draft-ietf-hip-rfc4423-bis-20.txt   rfc9063.txt 
Network Working Group R. Moskowitz, Ed. Internet Engineering Task Force (IETF) R. Moskowitz, Ed.
Internet-Draft HTT Consulting Request for Comments: 9063 HTT Consulting
Obsoletes: 4423 (if approved) M. Komu Obsoletes: 4423 M. Komu
Intended status: Informational Ericsson Category: Informational Ericsson
Expires: August 18, 2019 February 14, 2019 ISSN: 2070-1721 July 2021
Host Identity Protocol Architecture Host Identity Protocol Architecture
draft-ietf-hip-rfc4423-bis-20
Abstract Abstract
This memo describes the Host Identity (HI) namespace, that provides a This memo describes the Host Identity (HI) namespace, which provides
cryptographic namespace to applications, and the associated protocol a cryptographic namespace to applications, and the associated
layer, the Host Identity Protocol, located between the protocol layer, the Host Identity Protocol, located between the
internetworking and transport layers, that supports end-host internetworking and transport layers, that supports end-host
mobility, multihoming and NAT traversal. Herein are presented the mobility, multihoming, and NAT traversal. Herein are presented the
basics of the current namespaces, their strengths and weaknesses, and basics of the current namespaces, their strengths and weaknesses, and
how a HI namespace will add completeness to them. The roles of the how a HI namespace will add completeness to them. The roles of the
HI namespace in the protocols are defined. HI namespace in the protocols are defined.
This document obsoletes RFC 4423 and addresses the concerns raised by This document obsoletes RFC 4423 and addresses the concerns raised by
the IESG, particularly that of crypto agility. The section on the IESG, particularly that of crypto agility. The Security
security considerations describe also measures against flooding Considerations section also describes measures against flooding
attacks, usage of identities in access control lists, weaker types of attacks, usage of identities in access control lists, weaker types of
identifiers and trust on first use. This document incorporates identifiers, and trust on first use. This document incorporates
lessons learned from the implementations of RFC 5201 and goes further lessons learned from the implementations of RFC 7401 and goes further
to explain how HIP works as a secure signaling channel. to explain how HIP works as a secure signaling channel.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for informational purposes.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on August 18, 2019. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9063.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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skipping to change at page 2, line 34 skipping to change at line 74
modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
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than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology
2.1. Terms common to other documents . . . . . . . . . . . . . . 4 2.1. Terms Common to Other Documents
2.2. Terms specific to this and other HIP documents . . . . . . 5 2.2. Terms Specific to This and Other HIP Documents
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Background
3.1. A desire for a namespace for computing platforms . . . . . 8 3.1. A Desire for a Namespace for Computing Platforms
4. Host Identity namespace . . . . . . . . . . . . . . . . . . . 9 4. Host Identity Namespace
4.1. Host Identifiers . . . . . . . . . . . . . . . . . . . . . 10 4.1. Host Identifiers
4.2. Host Identity Hash (HIH) . . . . . . . . . . . . . . . . . 11 4.2. Host Identity Hash (HIH)
4.3. Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . . 11 4.3. Host Identity Tag (HIT)
4.4. Local Scope Identifier (LSI) . . . . . . . . . . . . . . . 12 4.4. Local Scope Identifier (LSI)
4.5. Storing Host Identifiers in directories . . . . . . . . . . 13 4.5. Storing Host Identifiers in Directories
5. New stack architecture . . . . . . . . . . . . . . . . . . . 14 5. New Stack Architecture
5.1. On the multiplicity of identities . . . . . . . . . . . . . 15 5.1. On the Multiplicity of Identities
6. Control plane . . . . . . . . . . . . . . . . . . . . . . . . 16 6. Control Plane
6.1. Base exchange . . . . . . . . . . . . . . . . . . . . . . . 16 6.1. Base Exchange
6.2. End-host mobility and multi-homing . . . . . . . . . . . . 17 6.2. End-Host Mobility and Multihoming
6.3. Rendezvous mechanism . . . . . . . . . . . . . . . . . . . 18 6.3. Rendezvous Mechanism
6.4. Relay mechanism . . . . . . . . . . . . . . . . . . . . . . 18 6.4. Relay Mechanism
6.5. Termination of the control plane . . . . . . . . . . . . . 18 6.5. Termination of the Control Plane
7. Data plane . . . . . . . . . . . . . . . . . . . . . . . . . 18 7. Data Plane
8. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . . . 19 8. HIP and NATs
8.1. HIP and Upper-layer checksums . . . . . . . . . . . . . . . 20 8.1. HIP and Upper-Layer Checksums
9. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . . 20 9. Multicast
10. HIP policies . . . . . . . . . . . . . . . . . . . . . . . . 21 10. HIP Policies
11. Security considerations . . . . . . . . . . . . . . . . . . . 21 11. Security Considerations
11.1. MiTM Attacks . . . . . . . . . . . . . . . . . . . . . . . 22 11.1. MitM Attacks
11.2. Protection against flooding attacks . . . . . . . . . . . 23 11.2. Protection against Flooding Attacks
11.3. HITs used in ACLs . . . . . . . . . . . . . . . . . . . . 24 11.3. HITs Used in ACLs
11.4. Alternative HI considerations . . . . . . . . . . . . . . 25 11.4. Alternative HI Considerations
11.5. Trust On First Use . . . . . . . . . . . . . . . . . . . . 25 11.5. Trust on First Use
12. IANA considerations . . . . . . . . . . . . . . . . . . . . . 28 12. IANA Considerations
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28 13. Changes from RFC 4423
14. Changes from RFC 4423 . . . . . . . . . . . . . . . . . . . . 29 14. References
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 29 14.1. Normative References
15.1. Normative References . . . . . . . . . . . . . . . . . . . 29 14.2. Informative References
15.2. Informative references . . . . . . . . . . . . . . . . . . 31 Appendix A. Design Considerations
Appendix A. Design considerations . . . . . . . . . . . . . . . 38 A.1. Benefits of HIP
A.1. Benefits of HIP . . . . . . . . . . . . . . . . . . . . . . 38 A.2. Drawbacks of HIP
A.2. Drawbacks of HIP . . . . . . . . . . . . . . . . . . . . . 41 A.3. Deployment and Adoption Considerations
A.3. Deployment and adoption considerations . . . . . . . . . . 43 A.3.1. Deployment Analysis
A.3.1. Deployment analysis . . . . . . . . . . . . . . . . . . . 43 A.3.2. HIP in 802.15.4 Networks
A.3.2. HIP in 802.15.4 networks . . . . . . . . . . . . . . . . 44 A.3.3. HIP and Internet of Things
A.3.3. HIP and Internet of Things . . . . . . . . . . . . . . . 44 A.3.4. Infrastructure Applications
A.3.4. Infrastructure Applications . . . . . . . . . . . . . . . 46 A.3.5. Management of Identities in a Commercial Product
A.3.5. Management of Identities in a Commercial Product . . . . 47 A.4. Answers to NSRG Questions
A.4. Answers to NSRG questions . . . . . . . . . . . . . . . . . 48 Acknowledgments
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50 Authors' Addresses
1. Introduction 1. Introduction
The Internet has two important global namespaces: Internet Protocol The Internet has two important global namespaces: Internet Protocol
(IP) addresses and Domain Name Service (DNS) names. These two (IP) addresses and Domain Name Service (DNS) names. These two
namespaces have a set of features and abstractions that have powered namespaces have a set of features and abstractions that have powered
the Internet to what it is today. They also have a number of the Internet to what it is today. They also have a number of
weaknesses. Basically, since they are all we have, we try to do too weaknesses. Basically, since they are all we have, we try to do too
much with them. Semantic overloading and functionality extensions much with them. Semantic overloading and functionality extensions
have greatly complicated these namespaces. have greatly complicated these namespaces.
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Identity conceptually refers to a computing platform, and there may Identity conceptually refers to a computing platform, and there may
be multiple such Host Identities per computing platform (because the be multiple such Host Identities per computing platform (because the
platform may wish to present a different identity to different platform may wish to present a different identity to different
communicating peers). The Host Identity namespace consists of Host communicating peers). The Host Identity namespace consists of Host
Identifiers (HI). There is exactly one Host Identifier for each Host Identifiers (HI). There is exactly one Host Identifier for each Host
Identity (although there may be transient periods of time such as key Identity (although there may be transient periods of time such as key
replacement when more than one identifier may be active). While this replacement when more than one identifier may be active). While this
text later talks about non-cryptographic Host Identifiers, the text later talks about non-cryptographic Host Identifiers, the
architecture focuses on the case in which Host Identifiers are architecture focuses on the case in which Host Identifiers are
cryptographic in nature. Specifically, the Host Identifier is the cryptographic in nature. Specifically, the Host Identifier is the
public key of an asymmetric key-pair. Each Host Identity uniquely public key of an asymmetric key pair. Each Host Identity uniquely
identifies a single host, i.e., no two hosts have the same Host identifies a single host, i.e., no two hosts have the same Host
Identity. If two or more computing platforms have the same Host Identity. If two or more computing platforms have the same Host
Identifier, then they are instantiating a distributed host. The Host Identifier, then they are instantiating a distributed host. The Host
Identifier can either be public (e.g., published in the DNS), or Identifier can either be public (e.g., published in the DNS) or
unpublished. Client systems will tend to have both public and unpublished. Client systems will tend to have both public and
unpublished Host Identifiers. unpublished Host Identifiers.
There is a subtle but important difference between Host Identities There is a subtle but important difference between Host Identities
and Host Identifiers. An Identity refers to the abstract entity that and Host Identifiers. An Identity refers to the abstract entity that
is identified. An Identifier, on the other hand, refers to the is identified. An Identifier, on the other hand, refers to the
concrete bit pattern that is used in the identification process. concrete bit pattern that is used in the identification process.
Although the Host Identifiers could be used in many authentication Although the Host Identifiers could be used in many authentication
systems, such as IKEv2 [RFC4306], the presented architecture systems, such as IKEv2 [RFC7296], the presented architecture
introduces a new protocol, called the Host Identity Protocol (HIP), introduces a new protocol, called the Host Identity Protocol (HIP),
and a cryptographic exchange, called the HIP base exchange; see also and a cryptographic exchange, called the HIP base exchange; see also
Section 6. HIP provides for limited forms of trust between systems, Section 6. HIP provides for limited forms of trust between systems,
enhances mobility, multi-homing and dynamic IP renumbering, aids in enhances mobility, multihoming, and dynamic IP renumbering, aids in
protocol translation / transition, and reduces certain types of protocol translation and transition, and reduces certain types of
denial-of-service (DoS) attacks. denial-of-service (DoS) attacks.
When HIP is used, the actual payload traffic between two HIP hosts is When HIP is used, the actual payload traffic between two HIP hosts is
typically, but not necessarily, protected with ESP [RFC7402]. The typically, but not necessarily, protected with Encapsulating Security
Host Identities are used to create the needed ESP Security Payload (ESP) [RFC7402]. The Host Identities are used to create the
Associations (SAs) and to authenticate the hosts. When ESP is used, needed ESP Security Associations (SAs) and to authenticate the hosts.
the actual payload IP packets do not differ in any way from standard When ESP is used, the actual payload IP packets do not differ in any
ESP protected IP packets. way from standard ESP-protected IP packets.
Much has been learned about HIP [RFC6538] since [RFC4423] was Much has been learned about HIP [RFC6538] since [RFC4423] was
published. This document expands Host Identities beyond use to published. This document expands Host Identities beyond their
enable IP connectivity and security to general interhost secure original use to enable IP connectivity and security to enable general
signalling at any protocol layer. The signal may establish a interhost secure signaling at any protocol layer. The signal may
security association between the hosts, or simply pass information establish a security association between the hosts or simply pass
within the channel. information within the channel.
2. Terminology 2. Terminology
2.1. Terms common to other documents 2.1. Terms Common to Other Documents
+---------------+---------------------------------------------------+
| Term | Explanation |
+---------------+---------------------------------------------------+
| Public key | The public key of an asymmetric cryptographic key |
| | pair. Used as a publicly known identifier for |
| | cryptographic identity authentication. Public is |
| | a relative term here, ranging from "known to |
| | peers only" to "known to the world." |
| Private key | The private or secret key of an asymmetric |
| | cryptographic key pair. Assumed to be known only |
| | to the party identified by the corresponding |
| | public key. Used by the identified party to |
| | authenticate its identity to other parties. |
| Public key | An asymmetric cryptographic key pair consisting |
| pair | of public and private keys. For example, Rivest- |
| | Shamir-Adleman (RSA), Digital Signature Algorithm |
| | (DSA) and Elliptic Curve DSA (ECDSA) key pairs |
| | are such key pairs. |
| End-point | A communicating entity. For historical reasons, |
| | the term 'computing platform' is used in this |
| | document as a (rough) synonym for end-point. |
+---------------+---------------------------------------------------+
2.2. Terms specific to this and other HIP documents +==========+===================================================+
| Term | Explanation |
+==========+===================================================+
| Public | The public key of an asymmetric cryptographic key |
| key | pair. Used as a publicly known identifier for |
| | cryptographic identity authentication. Public is |
| | a relative term here, ranging from "known to |
| | peers only" to "known to the world". |
+----------+---------------------------------------------------+
| Private | The private or secret key of an asymmetric |
| key | cryptographic key pair. Assumed to be known only |
| | to the party identified by the corresponding |
| | public key. Used by the identified party to |
| | authenticate its identity to other parties. |
+----------+---------------------------------------------------+
| Public | An asymmetric cryptographic key pair consisting |
| key pair | of public and private keys. For example, Rivest- |
| | Shamir-Adleman (RSA), Digital Signature Algorithm |
| | (DSA) and Elliptic Curve DSA (ECDSA) key pairs |
| | are such key pairs. |
+----------+---------------------------------------------------+
| Endpoint | A communicating entity. For historical reasons, |
| | the term 'computing platform' is used in this |
| | document as a (rough) synonym for endpoint. |
+----------+---------------------------------------------------+
Table 1
2.2. Terms Specific to This and Other HIP Documents
It should be noted that many of the terms defined herein are It should be noted that many of the terms defined herein are
tautologous, self-referential or defined through circular reference tautologous, self-referential, or defined through circular reference
to other terms. This is due to the succinct nature of the to other terms. This is due to the succinct nature of the
definitions. See the text elsewhere in this document and the base definitions. See the text elsewhere in this document and the base
specification [RFC7401] for more elaborate explanations. specification [RFC7401] for more elaborate explanations.
+---------------+---------------------------------------------------+ +==============+=============================================+
| Term | Explanation | | Term | Explanation |
+---------------+---------------------------------------------------+ +==============+=============================================+
| Computing | An entity capable of communicating and computing, | | Computing | An entity capable of communicating and |
| platform | for example, a computer. See the definition of | | platform | computing, for example, a computer. See |
| | 'End-point', above. | | | the definition of 'Endpoint', above. |
| | | +--------------+---------------------------------------------+
| HIP base | A cryptographic protocol; see also Section 6 | | HIP base | A cryptographic protocol; see also |
| exchange | | | exchange | Section 6. |
| | | +--------------+---------------------------------------------+
| HIP packet | An IP packet that carries a 'Host Identity | | HIP packet | An IP packet that carries a 'Host Identity |
| | Protocol' message. | | | Protocol' message. |
| | | +--------------+---------------------------------------------+
| Host Identity | An abstract concept assigned to a 'computing | | Host | An abstract concept assigned to a |
| | platform'. See 'Host Identifier', below. | | Identity | 'computing platform'. See 'Host |
| | | | | Identifier', below. |
| Host | A public key used as a name for a Host Identity. | +--------------+---------------------------------------------+
| Identifier | | | Host | A public key used as a name for a Host |
| | | | Identifier | Identity. |
| Host Identity | A name space formed by all possible Host | +--------------+---------------------------------------------+
| namespace | Identifiers. | | Host | A name space formed by all possible Host |
| | | | Identity | Identifiers. |
| Host Identity | A protocol used to carry and authenticate Host | | namespace | |
| Protocol | Identifiers and other information. | +--------------+---------------------------------------------+
| | | | Host | A protocol used to carry and authenticate |
| Host Identity | The cryptographic hash used in creating the Host | | Identity | Host Identifiers and other information. |
| Hash | Identity Tag from the Host Identifier. | | Protocol | |
| | | +--------------+---------------------------------------------+
| Host Identity | A 128-bit datum created by taking a cryptographic | | Host | The cryptographic hash used in creating the |
| Tag | hash over a Host Identifier plus bits to identify | | Identity | Host Identity Tag from the Host Identifier. |
| | which hash used. | | Hash | |
| | | +--------------+---------------------------------------------+
| Local Scope | A 32-bit datum denoting a Host Identity. | | Host | A 128-bit datum created by taking a |
| Identifier | | | Identity Tag | cryptographic hash over a Host Identifier |
| | | | | plus bits to identify which hash was used. |
| Public Host | A published or publicly known Host Identifier | +--------------+---------------------------------------------+
| Identifier | used as a public name for a Host Identity, and | | Local Scope | A 32-bit datum denoting a Host Identity. |
| and Identity | the corresponding Identity. | | Identifier | |
| | | +--------------+---------------------------------------------+
| Unpublished | A Host Identifier that is not placed in any | | Public Host | A published or publicly known Host |
| Host | public directory, and the corresponding Host | | Identifier | Identifier used as a public name for a Host |
| Identifier | Identity. Unpublished Host Identities are | | and Identity | Identity, and the corresponding Identity. |
| and Identity | typically short lived in nature, being often | +--------------+---------------------------------------------+
| | replaced and possibly used just once. | | Unpublished | A Host Identifier that is not placed in any |
| | | | Host | public directory, and the corresponding |
| Rendezvous | A mechanism used to locate mobile hosts based on | | Identifier | Host Identity. Unpublished Host Identities |
| Mechanism | their HIT. | | and Identity | are typically short lived in nature, being |
+---------------+---------------------------------------------------+ | | often replaced and possibly used just once. |
+--------------+---------------------------------------------+
| Rendezvous | A mechanism used to locate mobile hosts |
| Mechanism | based on their HIT. |
+--------------+---------------------------------------------+
Table 2
3. Background 3. Background
The Internet is built from three principal components: computing The Internet is built from three principal components: computing
platforms (end-points), packet transport (i.e., internetworking) platforms (endpoints), packet transport (i.e., internetworking)
infrastructure, and services (applications). The Internet exists to infrastructure, and services (applications). The Internet exists to
service two principal components: people and robotic services service two principal components: people and robotic services
(silicon-based people, if you will). All these components need to be (silicon-based people, if you will). All these components need to be
named in order to interact in a scalable manner. Here we concentrate named in order to interact in a scalable manner. Here we concentrate
on naming computing platforms and packet transport elements. on naming computing platforms and packet transport elements.
There are two principal namespaces in use in the Internet for these There are two principal namespaces in use in the Internet for these
components: IP addresses, and Domain Names. Domain Names provide components: IP addresses, and Domain Names. Domain Names provide
hierarchically assigned names for some computing platforms and some hierarchically assigned names for some computing platforms and some
services. Each hierarchy is delegated from the level above; there is services. Each hierarchy is delegated from the level above; there is
no anonymity in Domain Names. Email, HTTP, and SIP addresses all no anonymity in Domain Names. Email, HTTP, and SIP addresses all
reference Domain Names. reference Domain Names.
The IP addressing namespace has been overloaded to name both The IP addressing namespace has been overloaded to name both
interfaces (at layer-3) and endpoints (for the endpoint-specific part interfaces (at Layer 3) and endpoints (for the endpoint-specific part
of layer-3, and for layer-4). In their role as interface names, IP of Layer 3 and for Layer 4). In their role as interface names, IP
addresses are sometimes called "locators" and serve as an endpoint addresses are sometimes called "locators" and serve as an endpoint
within a routing topology. within a routing topology.
IP addresses are numbers that name networking interfaces, and IP addresses are numbers that name networking interfaces, and
typically only when the interface is connected to the network. typically only when the interface is connected to the network.
Originally, IP addresses had long-term significance. Today, the vast Originally, IP addresses had long-term significance. Today, the vast
number of interfaces use ephemeral and/or non-unique IP addresses. number of interfaces use ephemeral and/or non-unique IP addresses.
That is, every time an interface is connected to the network, it is That is, every time an interface is connected to the network, it is
assigned an IP address. assigned an IP address.
In the current Internet, the transport layers are coupled to the IP In the current Internet, the transport layers are coupled to the IP
addresses. Neither can evolve separately from the other. IPng addresses. Neither can evolve separately from the other. IPng
deliberations were strongly shaped by the decision that a deliberations were strongly shaped by the decision that a
corresponding TCPng would not be created. corresponding TCPng would not be created.
There are three critical deficiencies with the current namespaces. There are three critical deficiencies with the current namespaces.
Firstly, establishing initial contact and sustaining of data flows First, the establishing of initial contact and the sustaining of data
between two hosts can be challenging due to private address realms flows between two hosts can be challenging due to private address
and ephemeral nature of addresses. Secondly, confidentiality is not realms and the ephemeral nature of addresses. Second,
provided in a consistent, trustable manner. Finally, authentication confidentiality is not provided in a consistent, trustable manner.
for systems and datagrams is not provided. All of these deficiencies Finally, authentication for systems and datagrams is not provided.
arise because computing platforms are not well named with the current All of these deficiencies arise because computing platforms are not
namespaces. well named with the current namespaces.
3.1. A desire for a namespace for computing platforms 3.1. A Desire for a Namespace for Computing Platforms
An independent namespace for computing platforms could be used in An independent namespace for computing platforms could be used in
end-to-end operations independent of the evolution of the end-to-end operations independent of the evolution of the
internetworking layer and across the many internetworking layers. internetworking layer and across the many internetworking layers.
This could support rapid readdressing of the internetworking layer This could support rapid readdressing of the internetworking layer
because of mobility, rehoming, or renumbering. because of mobility, rehoming, or renumbering.
If the namespace for computing platforms is based on public-key If the namespace for computing platforms is based on public-key
cryptography, it can also provide authentication services. If this cryptography, it can also provide authentication services. If this
namespace is locally created without requiring registration, it can namespace is locally created without requiring registration, it can
provide anonymity. provide anonymity.
Such a namespace (for computing platforms) and the names in it should Such a namespace (for computing platforms) and the names in it should
have the following characteristics: have the following characteristics:
o The namespace should be applied to the IP 'kernel' or stack. The * The namespace should be applied to the IP 'kernel' or stack. The
IP stack is the 'component' between applications and the packet IP stack is the 'component' between applications and the packet
transport infrastructure. transport infrastructure.
o The namespace should fully decouple the internetworking layer from * The namespace should fully decouple the internetworking layer from
the higher layers. The names should replace all occurrences of IP the higher layers. The names should replace all occurrences of IP
addresses within applications (like in the Transport Control addresses within applications (like in the Transport Control
Block, TCB). This replacement can be handled transparently for Block, TCB). This replacement can be handled transparently for
legacy applications as the LSIs and HITs are compatible with IPv4 legacy applications as the Local Scope Identifiers (LSIs) and HITs
and IPv6 addresses [RFC5338]. However, HIP-aware applications are compatible with IPv4 and IPv6 addresses [RFC5338]. However,
require some modifications from the developers, who may employ HIP-aware applications require some modifications from the
networking API extensions for HIP [RFC6317]. developers, who may employ networking API extensions for HIP
[RFC6317].
o The introduction of the namespace should not mandate any * The introduction of the namespace should not mandate any
administrative infrastructure. Deployment must come from the administrative infrastructure. Deployment must come from the
bottom up, in a pairwise deployment. bottom up, in a pairwise deployment.
o The names should have a fixed-length representation, for easy * The names should have a fixed-length representation, for easy
inclusion in datagram headers and existing programming interfaces inclusion in datagram headers and existing programming interfaces
(e.g the TCB). (e.g., the TCB).
o Using the namespace should be affordable when used in protocols. * Using the namespace should be affordable when used in protocols.
This is primarily a packet size issue. There is also a This is primarily a packet size issue. There is also a
computational concern in affordability. computational concern in affordability.
o Name collisions should be avoided as much as possible. The * Name collisions should be avoided as much as possible. The
mathematics of the birthday paradox can be used to estimate the mathematics of the birthday paradox can be used to estimate the
chance of a collision in a given population and hash space. In chance of a collision in a given population and hash space. In
general, for a random hash space of size n bits, we would expect general, for a random hash space of size n bits, we would expect
to obtain a collision after approximately 1.2*sqrt(2**n) hashes to obtain a collision after approximately 1.2*sqrt(2^n) hashes
were obtained. For 64 bits, this number is roughly 4 billion. A were obtained. For 64 bits, this number is roughly 4 billion. A
hash size of 64 bits may be too small to avoid collisions in a hash size of 64 bits may be too small to avoid collisions in a
large population; for example, there is a 1% chance of collision large population; for example, there is a 1% chance of collision
in a population of 640M. For 100 bits (or more), we would not in a population of 640M. For 100 bits (or more), we would not
expect a collision until approximately 2**50 (1 quadrillion) expect a collision until approximately 2^50 (1 quadrillion) hashes
hashes were generated. With the currently used hash size of 96 were generated. With the currently used hash size of 96 bits
bits [RFC7343], the figure is 2**48 (281 trillions). [RFC7343], the figure is 2^48 (281 trillions).
o The names should have a localized abstraction so that they can be * The names should have a localized abstraction so that they can be
used in existing protocols and APIs. used in existing protocols and APIs.
o It must be possible to create names locally. When such names are * It must be possible to create names locally. When such names are
not published, this can provide anonymity at the cost of making not published, this can provide anonymity at the cost of making
resolvability very difficult. resolvability very difficult.
o The namespace should provide authentication services. * The namespace should provide authentication services.
o The names should be long-lived, but replaceable at any time. This * The names should be long-lived, but replaceable at any time. This
impacts access control lists; short lifetimes will tend to result impacts access control lists; short lifetimes will tend to result
in tedious list maintenance or require a namespace infrastructure in tedious list maintenance or require a namespace infrastructure
for central control of access lists. for central control of access lists.
In this document, the namespace approaching these ideas is called the In this document, the namespace approaching these ideas is called the
Host Identity namespace. Using Host Identities requires its own Host Identity namespace. Using Host Identities requires its own
protocol layer, the Host Identity Protocol, between the protocol layer, the Host Identity Protocol, between the
internetworking and transport layers. The names are based on public- internetworking and transport layers. The names are based on public-
key cryptography to supply authentication services. Properly key cryptography to supply authentication services. Properly
designed, it can deliver all of the above-stated requirements. designed, it can deliver all of the above-stated requirements.
4. Host Identity namespace 4. Host Identity Namespace
A name in the Host Identity namespace, a Host Identifier (HI), A name in the Host Identity namespace, a Host Identifier (HI),
represents a statistically globally unique name for naming any system represents a statistically globally unique name for naming any system
with an IP stack. This identity is normally associated with, but not with an IP stack. This identity is normally associated with, but not
limited to, an IP stack. A system can have multiple identities, some limited to, an IP stack. A system can have multiple identities, some
'well known', some unpublished or 'anonymous'. A system may self- 'well known', some unpublished or 'anonymous'. A system may self-
assert its own identity, or may use a third-party authenticator like assert its own identity, or may use a third-party authenticator like
DNSSEC [RFC2535], PGP, or X.509 to 'notarize' the identity assertion DNSSEC [RFC4033], Pretty Good Privacy (PGP), or X.509 to 'notarize'
to another namespace. the identity assertion to another namespace.
In theory, any name that can claim to be 'statistically globally In theory, any name that can claim to be 'statistically globally
unique' may serve as a Host Identifier. In the HIP architecture, the unique' may serve as a Host Identifier. In the HIP architecture, the
public key of a private-public key pair has been chosen as the Host public key of a private-public key pair has been chosen as the Host
Identifier because it can be self-managed and it is computationally Identifier because it can be self-managed and it is computationally
difficult to forge. As specified in the Host Identity Protocol difficult to forge. As specified in the Host Identity Protocol
[RFC7401] specification, a public-key-based HI can authenticate the specification [RFC7401], a public-key-based HI can authenticate the
HIP packets and protect them from man-in-the-middle attacks. Since HIP packets and protect them from man-in-the-middle (MitM) attacks.
authenticated datagrams are mandatory to provide much of HIP's Since authenticated datagrams are mandatory to provide much of HIP's
denial-of-service protection, the Diffie-Hellman exchange in HIP base denial-of-service protection, the Diffie-Hellman exchange in HIP base
exchange has to be authenticated. Thus, only public-key HI and exchange has to be authenticated. Thus, only public-key HI and
authenticated HIP messages are supported in practice. authenticated HIP messages are supported in practice.
In this document, some non-cryptographic forms of HI and HIP are In this document, some non-cryptographic forms of HI and HIP are
referenced, but cryptographic forms SHOULD be preferred because they referenced, but cryptographic forms should be preferred because they
are more secure than their non-cryptographic counterparts. There has are more secure than their non-cryptographic counterparts. There has
been past research in challenge puzzles to use non-cryptographic HI, been past research in challenge puzzles using non-cryptographic HI
for Radio Frequency IDentification (RFID), in an HIP exchange for Radio Frequency IDentification (RFID), in an HIP exchange
tailored to the workings of such challenges (as described further in tailored to the workings of such challenges (as described further in
[urien-rfid] and [urien-rfid-draft]). [urien-rfid] and [urien-rfid-draft]).
4.1. Host Identifiers 4.1. Host Identifiers
Host Identity adds two main features to Internet protocols. The Host Identity adds two main features to Internet protocols. The
first is a decoupling of the internetworking and transport layers; first is a decoupling of the internetworking and transport layers;
see Section 5. This decoupling will allow for independent evolution see Section 5. This decoupling will allow for independent evolution
of the two layers. Additionally, it can provide end-to-end services of the two layers. Additionally, it can provide end-to-end services
skipping to change at page 10, line 35 skipping to change at line 447
An identity is based on public-private key cryptography in HIP. The An identity is based on public-private key cryptography in HIP. The
Host Identity is referred to by its public component, the public key. Host Identity is referred to by its public component, the public key.
Thus, the name representing a Host Identity in the Host Identity Thus, the name representing a Host Identity in the Host Identity
namespace, i.e., the Host Identifier, is the public key. In a way, namespace, i.e., the Host Identifier, is the public key. In a way,
the possession of the private key defines the Identity itself. If the possession of the private key defines the Identity itself. If
the private key is possessed by more than one node, the Identity can the private key is possessed by more than one node, the Identity can
be considered to be a distributed one. be considered to be a distributed one.
Architecturally, any other Internet naming convention might form a Architecturally, any other Internet naming convention might form a
usable base for Host Identifiers. However, non-cryptographic names usable base for Host Identifiers. However, non-cryptographic names
should only be used in situations of high trust - low risk. That is should only be used in situations of high trust and/or low risk.
any place where host authentication is not needed (no risk of host That is any place where host authentication is not needed (no risk of
spoofing) and no use of ESP. However, at least for interconnected host spoofing) and no use of ESP. However, at least for
networks spanning several operational domains, the set of interconnected networks spanning several operational domains, the set
environments where the risk of host spoofing allowed by non- of environments where the risk of host spoofing allowed by non-
cryptographic Host Identifiers is acceptable is the null set. Hence, cryptographic Host Identifiers is acceptable is the null set. Hence,
the current HIP documents do not specify how to use any other types the current HIP documents do not specify how to use any other types
of Host Identifiers but public keys. For instance, Back-to-My-Mac of Host Identifiers but public keys. For instance, the Back to My
[RFC6281] from Apple comes pretty close to the functionality of HIP, Mac service [RFC6281] from Apple comes pretty close to the
but unlike HIP, it is based on non-cryptographic identifiers. functionality of HIP, but unlike HIP, it is based on non-
cryptographic identifiers.
The actual Host Identifiers are never directly used at the transport The actual Host Identifiers are never directly used at the transport
or network layers. The corresponding Host Identifiers (public keys) or network layers. The corresponding Host Identifiers (public keys)
may be stored in various DNS or other directories as identified may be stored in various DNS or other directories as identified
elsewhere in this document, and they are passed in the HIP base elsewhere in this document, and they are passed in the HIP base
exchange. A Host Identity Tag (HIT) is used in other protocols to exchange. A Host Identity Tag (HIT) is used in other protocols to
represent the Host Identity. Another representation of the Host represent the Host Identity. Another representation of the Host
Identities, the Local Scope Identifier (LSI), can also be used in Identities, the Local Scope Identifier (LSI), can also be used in
protocols and APIs. protocols and APIs.
4.2. Host Identity Hash (HIH) 4.2. Host Identity Hash (HIH)
The Host Identity Hash (HIH) is the cryptographic hash algorithm used The Host Identity Hash (HIH) is the cryptographic hash algorithm used
in producing the HIT from the HI. It is also the hash used in producing the HIT from the HI. It is also the hash used
throughout the HIP protocol for consistency and simplicity. It is throughout HIP for consistency and simplicity. It is possible for
possible for the two hosts in the HIP exchange to use different hash the two hosts in the HIP exchange to use different hash algorithms.
algorithms.
Multiple HIHs within HIP are needed to address the moving target of Multiple HIHs within HIP are needed to address the moving target of
creation and eventual compromise of cryptographic hashes. This creation and eventual compromise of cryptographic hashes. This
significantly complicates HIP and offers an attacker an additional significantly complicates HIP and offers an attacker an additional
downgrade attack that is mitigated in the HIP protocol [RFC7401]. downgrade attack that is mitigated in HIP [RFC7401].
4.3. Host Identity Tag (HIT) 4.3. Host Identity Tag (HIT)
A Host Identity Tag (HIT) is a 128-bit representation for a Host A Host Identity Tag (HIT) is a 128-bit representation for a Host
Identity. Due to its size, it is suitable to be used in the existing Identity. Due to its size, it is suitable for use in the existing
sockets API in the place of IPv6 addresses (e.g., in sockaddr_in6 sockets API in the place of IPv6 addresses (e.g., in sockaddr_in6
structure, sin6_addr member) without modifying applications. It is structure, sin6_addr member) without modifying applications. It is
created from an HIH, an IPv6 prefix [RFC7343] and a hash identifier. created from an HIH, an IPv6 prefix [RFC7343], and a hash identifier.
There are two advantages of using the HIT over using the Host There are two advantages of using the HIT over using the Host
Identifier in protocols. Firstly, its fixed length makes for easier Identifier in protocols. First, its fixed length makes for easier
protocol coding and also better manages the packet size cost of this protocol coding and also better manages the packet size cost of this
technology. Secondly, it presents the identity in a consistent technology. Second, it presents the identity in a consistent format
format to the protocol independent of the cryptographic algorithms to the protocol independent of the cryptographic algorithms used.
used.
In essence, the HIT is a hash over the public key. As such, two In essence, the HIT is a hash over the public key. As such, two
algorithms affect the generation of a HIT: the public-key algorithm algorithms affect the generation of a HIT: the public-key algorithm
of the HI and the used HIH. The two algorithms are encoded in the of the HI and the used HIH. The two algorithms are encoded in the
bit presentation of the HIT. As the two communicating parties may bit presentation of the HIT. As the two communicating parties may
support different algorithms, [RFC7401] defines the minimum set for support different algorithms, [RFC7401] defines the minimum set for
interoperability. For further interoperability, the responder may interoperability. For further interoperability, the Responder may
store its keys in DNS records, and thus the initiator may have to store its keys in DNS records, and thus the Initiator may have to
couple destination HITs with appropriate source HITs according to couple destination HITs with appropriate source HITs according to
matching HIH. matching HIH.
In the HIP packets, the HITs identify the sender and recipient of a In the HIP packets, the HITs identify the sender and recipient of a
packet. Consequently, a HIT should be unique in the whole IP packet. Consequently, a HIT should be unique in the whole IP
universe as long as it is being used. In the extremely rare case of universe as long as it is being used. In the extremely rare case of
a single HIT mapping to more than one Host Identity, the Host a single HIT mapping to more than one Host Identity, the Host
Identifiers (public keys) will make the final difference. If there Identifiers (public keys) will make the final difference. If there
is more than one public key for a given node, the HIT acts as a hint is more than one public key for a given node, the HIT acts as a hint
for the correct public key to use. for the correct public key to use.
Although it may be rare for an accidental collision to cause a single Although it may be rare for an accidental collision to cause a single
HIT mapping to more than one Host Identity, it may be the case that HIT mapping to more than one Host Identity, it may be the case that
an attacker succeeds to find, by brute force or algorithmic weakness, an attacker succeeds to find, by brute force or algorithmic weakness,
a second Host Identity hashing to the same HIT. This type of attack a second Host Identity hashing to the same HIT. This type of attack
is known as a preimage attack, and the resistance to finding a second is known as a preimage attack, and the resistance to finding a second
Host Identifier (public key) that hashes to the same HIT is called Host Identifier (public key) that hashes to the same HIT is called
second preimage resistance. Second preimage resistance in HIP is second preimage resistance. Second preimage resistance in HIP is
based on the hash algorithm strength and the length of the hash based on the hash algorithm strength and the length of the hash
output used. Through HIPv2 [RFC7401], this resistance is 96 bits output used. Through HIPv2 [RFC7401], this resistance is 96 bits
(less than the 128 bit width of an IPv6 address field due to the (less than the 128-bit width of an IPv6 address field due to the
presence of the ORCHID prefix [RFC7343]). 96 bits of resistance was presence of the Overlay Routable Cryptographic Hash Identifiers
considered acceptable strength during the design of HIP, but may (ORCHID) prefix [RFC7343]). 96 bits of resistance was considered
eventually be considered insufficient for the threat model of an acceptable strength during the design of HIP but may eventually be
envisioned deployment. One possible mitigation would be to augment considered insufficient for the threat model of an envisioned
the use of HITs in the deployment with the HIs themselves (and deployment. One possible mitigation would be to augment the use of
mechanisms to securely bind the HIs to the HITs), so that the HI HITs in the deployment with the HIs themselves (and mechanisms to
becomes the final authority. It also may be possible to increase the securely bind the HIs to the HITs), so that the HI becomes the final
difficulty of brute force attack by making the generation of the HI authority. It also may be possible to increase the difficulty of a
more computationally difficult, such as the hash extension approach brute force attack by making the generation of the HI more
of SEND CGAs [RFC3972], although the HIP specifications through HIPv2 computationally difficult, such as the hash extension approach of
do not provide such a mechanism. Finally, deployments that do not Secure Neighbor Discovery Cryptographically Generated Addresses
use ORCHIDs (such as certain types of overlay networks) might also (CGAs) [RFC3972], although the HIP specifications through HIPv2 do
use the full 128-bit width of an IPv6 address field for the HIT. not provide such a mechanism. Finally, deployments that do not use
ORCHIDs (such as certain types of overlay networks) might also use
the full 128-bit width of an IPv6 address field for the HIT.
4.4. Local Scope Identifier (LSI) 4.4. Local Scope Identifier (LSI)
An LSI is a 32-bit localized representation for a Host Identity. Due An LSI is a 32-bit localized representation for a Host Identity. Due
to its size, it is suitable to be used in the existing sockets API in to its size, it is suitable for use in the existing sockets API in
the place of IPv4 addresses (e.g., in sockaddr_in structure, sin_addr the place of IPv4 addresses (e.g., in sockaddr_in structure, sin_addr
member) without modifying applications. The purpose of an LSI is to member) without modifying applications. The purpose of an LSI is to
facilitate using Host Identities in existing APIs for IPv4-based facilitate using Host Identities in existing APIs for IPv4-based
applications. LSIs are never transmitted on the wire; when an applications. LSIs are never transmitted on the wire; when an
application sends data using a pair of LSIs, the HIP layer (or application sends data using a pair of LSIs, the HIP layer (or
sockets handler) translates the LSIs to the corresponding HITs, and sockets handler) translates the LSIs to the corresponding HITs, and
vice versa for receiving of data. Besides facilitating HIP-based vice versa for the receiving of data. Besides facilitating HIP-based
connectivity for legacy IPv4 applications, the LSIs are beneficial in connectivity for legacy IPv4 applications, the LSIs are beneficial in
two other scenarios [RFC6538]. two other scenarios [RFC6538].
In the first scenario, two IPv4-only applications are residing on two In the first scenario, two IPv4-only applications reside on two
separate hosts connected by IPv6-only network. With HIP-based separate hosts connected by IPv6-only network. With HIP-based
connectivity, the two applications are able to communicate despite of connectivity, the two applications are able to communicate despite
the mismatch in the protocol families of the applications and the the mismatch in the protocol families of the applications and the
underlying network. The reason is that the HIP layer translates the underlying network. The reason is that the HIP layer translates the
LSIs originating from the upper layers into routable IPv6 locators LSIs originating from the upper layers into routable IPv6 locators
before delivering the packets on the wire. before delivering the packets on the wire.
The second scenario is the same as the first one, but with the The second scenario is the same as the first one, but with the
difference that one of the applications supports only IPv6. Now two difference that one of the applications supports only IPv6. Now two
obstacles hinder the communication between the application: the obstacles hinder the communication between the applications: the
addressing families of the two applications differ, and the addressing families of the two applications differ, and the
application residing at the IPv4-only side is again unable to application residing at the IPv4-only side is again unable to
communicate because of the mismatch between addressing families of communicate because of the mismatch between addressing families of
the application (IPv4) and network (IPv6). With HIP-based the application (IPv4) and network (IPv6). With HIP-based
connectivity for applications, this scenario works; the HIP layer can connectivity for applications, this scenario works; the HIP layer can
choose whether to translate the locator of an incoming packet into an choose whether to translate the locator of an incoming packet into an
LSI or HIT. LSI or HIT.
Effectively, LSIs improve IPv6 interoperability at the network layer Effectively, LSIs improve IPv6 interoperability at the network layer
as described in the first scenario and at the application layer as as described in the first scenario and at the application layer as
skipping to change at page 13, line 29 skipping to change at line 586
closed-source, IPv4-only applications may never see the daylight of closed-source, IPv4-only applications may never see the daylight of
IPv6, and the LSI mechanism is suitable for extending the lifetime of IPv6, and the LSI mechanism is suitable for extending the lifetime of
such applications even in IPv6-only networks. such applications even in IPv6-only networks.
The main disadvantage of an LSI is its local scope. Applications may The main disadvantage of an LSI is its local scope. Applications may
violate layering principles and pass LSIs to each other in violate layering principles and pass LSIs to each other in
application-layer protocols. As the LSIs are valid only in the application-layer protocols. As the LSIs are valid only in the
context of the local host, they may represent an entirely different context of the local host, they may represent an entirely different
host when passed to another host. However, it should be emphasized host when passed to another host. However, it should be emphasized
here that the LSI concept is effectively a host-based NAT and does here that the LSI concept is effectively a host-based NAT and does
not introduce any more issues than the prevalent middlebox based NATs not introduce any more issues than the prevalent middlebox-based NATs
for IPv4. In other words, the applications violating layering for IPv4. In other words, the applications violating layering
principles are already broken by the NAT boxes that are ubiquitously principles are already broken by the NAT boxes that are ubiquitously
deployed. deployed.
4.5. Storing Host Identifiers in directories 4.5. Storing Host Identifiers in Directories
The public Host Identifiers should be stored in DNS; the unpublished The public Host Identifiers should be stored in DNS; the unpublished
Host Identifiers should not be stored anywhere (besides the Host Identifiers should not be stored anywhere (besides the
communicating hosts themselves). The (public) HI along with the communicating hosts themselves). The (public) HI along with the
supported HIHs are stored in a new RR type. This RR type is defined supported HIHs are stored in a new Resource Record (RR) type. This
in HIP DNS Extension [RFC8005]. RR type is defined in the HIP DNS extension [RFC8005].
Alternatively, or in addition to storing Host Identifiers in the DNS, Alternatively, or in addition to storing Host Identifiers in the DNS,
they may be stored in various other directories. For instance, a they may be stored in various other directories. For instance, a
directory based on the Lightweight Directory Access Protocol (LDAP) directory based on the Lightweight Directory Access Protocol (LDAP)
or a Public Key Infrastructure (PKI) [RFC8002] may be used. or a Public Key Infrastructure (PKI) [RFC8002] may be used.
Alternatively, Distributed Hash Tables (DHTs) [RFC6537] have Alternatively, Distributed Hash Tables (DHTs) [RFC6537] have
successfully been utilized [RFC6538]. Such a practice may allow them successfully been utilized [RFC6538]. Such a practice may allow them
to be used for purposes other than pure host identification. to be used for purposes other than pure host identification.
Some types of applications may cache and use Host Identifiers Some types of applications may cache and use Host Identifiers
directly, while others may indirectly discover them through symbolic directly, while others may indirectly discover them through a
host name (such as FQDN) look up from a directory. Even though Host symbolic host name (such as a Fully Qualified Domain Name (FQDN))
Identities can have a substantially longer lifetime associated with look up from a directory. Even though Host Identities can have a
them than routable IP addresses, directories may be a better approach substantially longer lifetime associated with them than routable IP
to manage the lifespan of Host Identities. For example, an LDAP- addresses, directories may be a better approach to manage the
based directory or DHT can be used for locally published identities lifespan of Host Identities. For example, an LDAP-based directory or
whereas DNS can be more suitable for public advertisement. DHT can be used for locally published identities whereas DNS can be
more suitable for public advertisement.
5. New stack architecture 5. New Stack Architecture
One way to characterize Host Identity is to compare the proposed HI- One way to characterize Host Identity is to compare the proposed HI-
based architecture with the current one. Using the terminology from based architecture with the current one. Using the terminology from
the IRTF Name Space Research Group Report [nsrg-report] and, e.g., the IRTF Name Space Research Group Report [nsrg-report] and, e.g.,
the unpublished Internet-Draft Endpoints and Endpoint Names the document on "Endpoints and Endpoint Names" [chiappa-endpoints],
[chiappa-endpoints], the IP addresses currently embody the dual role the IP addresses currently embody the dual role of locators and
of locators and end-point identifiers. That is, each IP address endpoint identifiers. That is, each IP address names a topological
names a topological location in the Internet, thereby acting as a location in the Internet, thereby acting as a routing direction
routing direction vector, or locator. At the same time, the IP vector, or locator. At the same time, the IP address names the
address names the physical network interface currently located at the physical network interface currently located at the point-of-
point-of-attachment, thereby acting as a end-point name. attachment, thereby acting as an endpoint name.
In the HIP architecture, the end-point names and locators are In the HIP architecture, the endpoint names and locators are
separated from each other. IP addresses continue to act as locators. separated from each other. IP addresses continue to act as locators.
The Host Identifiers take the role of end-point identifiers. It is The Host Identifiers take the role of endpoint identifiers. It is
important to understand that the end-point names based on Host important to understand that the endpoint names based on Host
Identities are slightly different from interface names; a Host Identities are slightly different from interface names; a Host
Identity can be simultaneously reachable through several interfaces. Identity can be simultaneously reachable through several interfaces.
The difference between the bindings of the logical entities are The difference between the bindings of the logical entities are
illustrated in Figure 1. The left side illustrates the current TCP/ illustrated in Figure 1. The left side illustrates the current TCP/
IP architecture and the right side the HIP-based architecture. IP architecture and the right side the HIP-based architecture.
Transport ---- Socket Transport ------ Socket Transport ---- Socket Transport ------ Socket
association | association | association | association |
| | | |
| | | |
| | | |
End-point | End-point --- Host Identity Endpoint | Endpoint --- Host Identity
\ | | \ | |
\ | | \ | |
\ | | \ | |
\ | | \ | |
Location --- IP address Location --- IP address Location --- IP address Location --- IP address
Figure 1 Figure 1
Architecturally, HIP provides for a different binding of transport- Architecturally, HIP provides for a different binding of transport-
layer protocols. That is, the transport-layer associations, i.e., layer protocols. That is, the transport-layer associations, i.e.,
TCP connections and UDP associations, are no longer bound to IP TCP connections and UDP associations, are no longer bound to IP
addresses but rather to Host Identities. In practice, the Host addresses but rather to Host Identities. In practice, the Host
Identities are exposed as LSIs and HITs for legacy applications and Identities are exposed as LSIs and HITs for legacy applications and
the transport layer to facilitate backward compatibility with the transport layer to facilitate backward compatibility with
existing networking APIs and stacks. existing networking APIs and stacks.
The HIP layer is logically located at layer 3.5, between the The HIP layer is logically located at Layer 3.5, between the
transport and network layers, in the networking stack. It acts as transport and network layers, in the networking stack. It acts as
shim layer for transport data utilizing LSIs or HITs, but leaves shim layer for transport data utilizing LSIs or HITs but leaves other
other data intact. The HIP layer translates between the two forms of data intact. The HIP layer translates between the two forms of HIP
HIP identifiers originating from the transport layer into routable identifiers originating from the transport layer into routable IPv4/
IPv4/IPv6 addresses for the network layer, and vice versa for the IPv6 addresses for the network layer and vice versa for the reverse
reverse direction. direction.
5.1. On the multiplicity of identities 5.1. On the Multiplicity of Identities
A host may have multiple identities both at the client and server A host may have multiple identities both at the client and server
side. This raises some additional concerns that are addressed in side. This raises some additional concerns that are addressed in
this section. this section.
For security reasons, it may be a bad idea to duplicate the same Host For security reasons, it may be a bad idea to duplicate the same Host
Identity on multiple hosts because the compromise of a single host Identity on multiple hosts because the compromise of a single host
taints the identities of the other hosts. Management of machines taints the identities of the other hosts. Management of machines
with identical Host Identities may also present other challenges and, with identical Host Identities may also present other challenges and,
therefore, it is advisable to have a unique identity for each host. therefore, it is advisable to have a unique identity for each host.
At the server side, utilizing DNS is a better alternative than a At the server side, utilizing DNS is a better alternative than a
shared Host Identity to implement load balancing. A single FQDN shared Host Identity to implement load balancing. A single FQDN
entry can be configured to refer to multiple Host Identities. Each entry can be configured to refer to multiple Host Identities. Each
of the FQDN entries can be associated with the related locators, or a of the FQDN entries can be associated with the related locators or
single shared locator in the case the servers are using the same HIP with a single shared locator in the case the servers are using the
rendezvous server Section 6.3 or HIP relay server Section 6.4. same HIP rendezvous server (Section 6.3) or HIP relay server
(Section 6.4).
Instead of duplicating identities, HIP opportunistic mode can be Instead of duplicating identities, HIP opportunistic mode can be
employed, where the initiator leaves out the identifier of the employed, where the Initiator leaves out the identifier of the
responder when initiating the key exchange and learns it upon the Responder when initiating the key exchange and learns it upon the
completion of the exchange. The tradeoffs are related to lowered completion of the exchange. The trade-offs are related to lowered
security guarantees, but a benefit of the approach is to avoid security guarantees, but a benefit of the approach is to avoid the
publishing of Host Identifiers in any directories [komu-leap]. Since publishing of Host Identifiers in any directories [komu-leap]. Since
many public servers already employ DNS as their directory, many public servers already employ DNS as their directory,
opportunistic mode may be more suitable for, e.g, peer-to-peer opportunistic mode may be more suitable for, e.g., peer-to-peer
connectivity. It is also worth noting that opportunistic mode is connectivity. It is also worth noting that opportunistic mode is
also required in practice when anycast IP addresses would be utilized also required in practice when anycast IP addresses would be utilized
as locators. as locators.
HIP opportunistic mode could be utilized in association with HIP HIP opportunistic mode could be utilized in association with HIP
rendezvous servers or HIP relay servers [komu-diss]. In such a rendezvous servers or HIP relay servers [komu-diss]. In such a
scenario, the Initiator sends an I1 message with a wildcard scenario, the Initiator sends an I1 message with a wildcard
destination HIT to the locator of a HIP rendezvous/relay server. destination HIT to the locator of a HIP rendezvous/relay server.
When the receiving rendezvous/relay server is serving multiple When the receiving rendezvous/relay server is serving multiple
registered Responders, the server can choose the ultimate destination registered Responders, the server can choose the ultimate destination
HIT, thus acting as a HIP based load balancer. However, this HIT, thus acting as a HIP-based load balancer. However, this
approach is still experimental and requires further investigation. approach is still experimental and requires further investigation.
At the client side, a host may have multiple Host Identities, for At the client side, a host may have multiple Host Identities, for
instance, for privacy purposes. Another reason can be that the instance, for privacy purposes. Another reason can be that the
person utilizing the host employs different identities for different person utilizing the host employs different identities for different
administrative domains as an extra security measure. If a HIP-aware administrative domains as an extra security measure. If a HIP-aware
middlebox, such as a HIP-based firewall, is on the path between the middlebox, such as a HIP-based firewall, is on the path between the
client and server, the user or the underlying system should carefully client and server, the user or the underlying system should carefully
choose the correct identity to avoid the firewall to unnecessarily choose the correct identity to avoid the firewall unnecessarily
drop HIP-based connectivity [komu-diss]. dropping HIP-based connectivity [komu-diss].
Similarly, a server may have multiple Host Identities. For instance, Similarly, a server may have multiple Host Identities. For instance,
a single web server may serve multiple different administrative a single web server may serve multiple different administrative
domains. Typically, the distinction is accomplished based on the DNS domains. Typically, the distinction is accomplished based on the DNS
name, but also the Host Identity could be used for this purpose. name, but also the Host Identity could be used for this purpose.
However, a more compelling reason to employ multiple identities are However, a more compelling reason to employ multiple identities is
HIP-aware firewalls that are unable see the HTTP traffic inside the the HIP-aware firewall that is unable to see the HTTP traffic inside
encrypted IPsec tunnel. In such a case, each service could be the encrypted IPsec tunnel. In such a case, each service could be
configured with a separate identity, thus allowing the firewall to configured with a separate identity, thus allowing the firewall to
segregate the different services of the single web server from each segregate the different services of the single web server from each
other [lindqvist-enterprise]. other [lindqvist-enterprise].
6. Control plane 6. Control Plane
HIP decouples control and data plane from each other. Two end-hosts HIP decouples the control and data planes from each other. Two end-
initialize the control plane using a key exchange procedure called hosts initialize the control plane using a key exchange procedure
the base exchange. The procedure can be assisted by HIP specific called the base exchange. The procedure can be assisted by HIP-
infrastructural intermediaries called rendezvous or relay servers. specific infrastructural intermediaries called rendezvous or relay
In the event of IP address changes, the end-hosts sustain control servers. In the event of IP address changes, the end-hosts sustain
plane connectivity with mobility and multihoming extensions. control plane connectivity with mobility and multihoming extensions.
Eventually, the end-hosts terminate the control plane and remove the Eventually, the end-hosts terminate the control plane and remove the
associated state. associated state.
6.1. Base exchange 6.1. Base Exchange
The base exchange is a key exchange procedure that authenticates the The base exchange is a key exchange procedure that authenticates the
initiator and responder to each other using their public keys. Initiator and Responder to each other using their public keys.
Typically, the initiator is the client-side host and the responder is Typically, the Initiator is the client-side host and the Responder is
the server-side host. The roles are used by the state machine of a the server-side host. The roles are used by the state machine of a
HIP implementation, but discarded upon successful completion. HIP implementation but then discarded upon successful completion.
The exchange consists of four messages during which the hosts also The exchange consists of four messages during which the hosts also
create symmetric keys to protect the control plane with Hash-based create symmetric keys to protect the control plane with Hash-based
message authentication codes (HMACs). The keys can be also used to Message Authentication Codes (HMACs). The keys can be also used to
protect the data plane, and IPsec ESP [RFC7402] is typically used as protect the data plane, and IPsec ESP [RFC7402] is typically used as
the data-plane protocol, albeit HIP can also accommodate others. the data plane protocol, albeit HIP can also accommodate others.
Both the control and data plane are terminated using a closing Both the control and data planes are terminated using a closing
procedure consisting of two messages. procedure consisting of two messages.
In addition, the base exchange also includes a computational puzzle In addition, the base exchange also includes a computational puzzle
[RFC7401] that the initiator must solve. The responder chooses the [RFC7401] that the Initiator must solve. The Responder chooses the
difficulty of the puzzle which permits the responder to delay new difficulty of the puzzle, which permits the Responder to delay new
incoming initiators according to local policies, for instance, when incoming Initiators according to local policies, for instance, when
the responder is under heavy load. The puzzle can offer some the Responder is under heavy load. The puzzle can offer some
resiliency against DoS attacks because the design of the puzzle resiliency against DoS attacks because the design of the puzzle
mechanism allows the responder to remain stateless until the very end mechanism allows the Responder to remain stateless until the very end
of the base exchange [aura-dos]. HIP puzzles have also been studied of the base exchange [aura-dos]. HIP puzzles have also been studied
under steady-state DDoS attacks [beal-dos], on multiple adversary under steady-state DDoS attacks [beal-dos], on multiple adversary
models with varying puzzle difficulties [tritilanunt-dos] and with models with varying puzzle difficulties [tritilanunt-dos], and with
ephemeral Host Identities [komu-mitigation]. ephemeral Host Identities [komu-mitigation].
6.2. End-host mobility and multi-homing 6.2. End-Host Mobility and Multihoming
HIP decouples the transport from the internetworking layer, and binds HIP decouples the transport from the internetworking layer and binds
the transport associations to the Host Identities (actually through the transport associations to the Host Identities (actually through
either the HIT or LSI). After the initial key exchange, the HIP either the HIT or LSI). After the initial key exchange, the HIP
layer maintains transport-layer connectivity and data flows using its layer maintains transport-layer connectivity and data flows using its
mobility [RFC8046] and multihoming [RFC8047] extensions. extensions for mobility [RFC8046] and multihoming [RFC8047].
Consequently, HIP can provide for a degree of internetworking Consequently, HIP can provide for a degree of internetworking
mobility and multi-homing at a low infrastructure cost. HIP mobility mobility and multihoming at a low infrastructure cost. HIP mobility
includes IP address changes (via any method) to either party. Thus, includes IP address changes (via any method) to either party. Thus,
a system is considered mobile if its IP address can change a system is considered mobile if its IP address can change
dynamically for any reason like PPP, DHCP, IPv6 prefix reassignments, dynamically for any reason like PPP, DHCP, IPv6 prefix reassignments,
or a NAT device remapping its translation. Likewise, a system is or a NAT device remapping its translation. Likewise, a system is
considered multi-homed if it has more than one globally routable IP considered multihomed if it has more than one globally routable IP
address at the same time. HIP links IP addresses together, when address at the same time. HIP links IP addresses together when
multiple IP addresses correspond to the same Host Identity. If one multiple IP addresses correspond to the same Host Identity. If one
address becomes unusable, or a more preferred address becomes address becomes unusable, or a more preferred address becomes
available, existing transport associations can easily be moved to available, existing transport associations can easily be moved to
another address. another address.
When a mobile node moves while communication is already on-going, When a mobile node moves while communication is ongoing, address
address changes are rather straightforward. The mobile node sends a changes are rather straightforward. The mobile node sends a HIP
HIP UPDATE packet to inform the peer of the new address(es), and the UPDATE packet to inform the peer of the new address(es), and the peer
peer then verifies that the mobile node is reachable through these then verifies that the mobile node is reachable through these
addresses. This way, the peer can avoid flooding attacks as further addresses. This way, the peer can avoid flooding attacks as further
discussed in Section 11.2. discussed in Section 11.2.
6.3. Rendezvous mechanism 6.3. Rendezvous Mechanism
Establishing a contact to a mobile, moving node is slightly more Establishing a contact to a mobile, moving node is slightly more
involved. In order to start the HIP exchange, the initiator node has involved. In order to start the HIP exchange, the Initiator node has
to know how to reach the mobile node. For instance, the mobile node to know how to reach the mobile node. For instance, the mobile node
can employ Dynamic DNS [RFC2136] to update its reachability can employ Dynamic DNS [RFC2136] to update its reachability
information in the DNS. To avoid the dependency to DNS, HIP provides information in the DNS. To avoid the dependency to DNS, HIP provides
its own HIP-specific alternative: the HIP rendezvous mechanism as its own HIP-specific alternative: the HIP rendezvous mechanism as
defined in HIP Rendezvous specifications [RFC8004]. defined in the HIP rendezvous specification [RFC8004].
Using the HIP rendezvous extensions, the mobile node keeps the Using the HIP rendezvous extensions, the mobile node keeps the
rendezvous infrastructure continuously updated with its current IP rendezvous infrastructure continuously updated with its current IP
address(es). The mobile nodes trusts the rendezvous mechanism in address(es). The mobile nodes trusts the rendezvous mechanism in
order to properly maintain their HIT and IP address mappings. order to properly maintain their HIT and IP address mappings.
The rendezvous mechanism is especially useful in scenarios where both The rendezvous mechanism is especially useful in scenarios where both
of the nodes are expected to change their address at the same time. of the nodes are expected to change their address at the same time.
In such a case, the HIP UPDATE packets will cross each other in the In such a case, the HIP UPDATE packets will cross each other in the
network and never reach the peer node. network and never reach the peer node.
6.4. Relay mechanism 6.4. Relay Mechanism
The HIP relay mechanism [I-D.ietf-hip-native-nat-traversal] is an The HIP relay mechanism [RFC9028] is an alternative to the HIP
alternative to the HIP rendezvous mechanism. The HIP relay mechanism rendezvous mechanism. The HIP relay mechanism is more suitable for
is more suitable for IPv4 networks with NATs because a HIP relay can IPv4 networks with NATs because a HIP relay can forward all control
forward all control and data plane communications in order to and data plane communications in order to guarantee successful NAT
guarantee successful NAT traversal. traversal.
6.5. Termination of the control plane 6.5. Termination of the Control Plane
The control plane between two hosts is terminated using a secure two- The control plane between two hosts is terminated using a secure two-
message exchange as specified in base exchange specification message exchange as specified in base exchange specification
[RFC7401]. The related state (i.e. host associations) should be [RFC7401]. The related state (i.e., host associations) should be
removed upon successful termination. removed upon successful termination.
7. Data plane 7. Data Plane
The encapsulation format for the data plane used for carrying the The encapsulation format for the data plane used for carrying the
application-layer traffic can be dynamically negotiated during the application-layer traffic can be dynamically negotiated during the
key exchange. For instance, HICCUPS extensions [RFC6078] define one key exchange. For instance, HICCUPS extensions [RFC6078] define one
way to transport application-layer datagrams directly over the HIP way to transport application-layer datagrams directly over the HIP
control plane, protected by asymmetric key cryptography. Also, SRTP control plane, protected by asymmetric key cryptography. Also,
has been considered as the data encapsulation protocol [hip-srtp]. Secure Real-time Transport Protocol (SRTP) has been considered as the
However, the most widely implemented method is the Encapsulated data encapsulation protocol [hip-srtp]. However, the most widely
Security Payload (ESP) [RFC7402] that is protected by symmetric keys implemented method is the Encapsulated Security Payload (ESP)
derived during the key exchange. ESP Security Associations (SAs) [RFC7402] that is protected by symmetric keys derived during the key
offer both confidentiality and integrity protection, of which the exchange. ESP Security Associations (SAs) offer both confidentiality
former can be disabled during the key exchange. In the future, other and integrity protection, of which the former can be disabled during
ways of transporting application-layer data may be defined. the key exchange. In the future, other ways of transporting
application-layer data may be defined.
The ESP SAs are established and terminated between the initiator and The ESP SAs are established and terminated between the Initiator and
the responder hosts. Usually, the hosts create at least two SAs, one the Responder hosts. Usually, the hosts create at least two SAs, one
in each direction (initiator-to-responder SA and responder-to- in each direction (Initiator-to-Responder SA and Responder-to-
initiator SA). If the IP addresses of either host changes, the HIP Initiator SA). If the IP addresses of either host changes, the HIP
mobility extensions can be used to re-negotiate the corresponding mobility extensions can be used to renegotiate the corresponding SAs.
SAs.
On the wire, the difference in the use of identifiers between the HIP On the wire, the difference in the use of identifiers between the HIP
control and data plane is that the HITs are included in all control control and data planes is that the HITs are included in all control
packets, but not in the data plane when ESP is employed. Instead, packets, but not in the data plane when ESP is employed. Instead,
the ESP employs SPI numbers that act as compressed HITs. Any HIP- the ESP employs Security Parameter Index (SPI) numbers that act as
aware middlebox (for instance, a HIP-aware firewall) interested in compressed HITs. Any HIP-aware middlebox (for instance, a HIP-aware
the ESP based data plane should keep track between the control and firewall) interested in the ESP-based data plane should keep track
data plane identifiers in order to associate them with each other. between the control and data plane identifiers in order to associate
them with each other.
Since HIP does not negotiate any SA lifetimes, all lifetimes are Since HIP does not negotiate any SA lifetimes, all lifetimes are
subject to local policy. The only lifetimes a HIP implementation subject to local policy. The only lifetimes a HIP implementation
must support are sequence number rollover (for replay protection), must support are sequence number rollover (for replay protection) and
and SA timeout. An SA times out if no packets are received using SA timeout. An SA times out if no packets are received using that
that SA. Implementations may support lifetimes for the various ESP SA. Implementations may support lifetimes for the various ESP
transforms and other data-plane protocols. transforms and other data plane protocols.
8. HIP and NATs 8. HIP and NATs
Passing packets between different IP addressing realms requires Passing packets between different IP addressing realms requires
changing IP addresses in the packet header. This may occur, for changing IP addresses in the packet header. This may occur, for
example, when a packet is passed between the public Internet and a example, when a packet is passed between the public Internet and a
private address space, or between IPv4 and IPv6 networks. The private address space, or between IPv4 and IPv6 networks. The
address translation is usually implemented as Network Address address translation is usually implemented as Network Address
Translation (NAT) [RFC3022] or NAT Protocol translation (NAT-PT) Translation (NAT) [RFC3022] or the historic NAT Protocol Translation
[RFC2766]. (NAT-PT) [RFC2766].
In a network environment where identification is based on the IP In a network environment where identification is based on the IP
addresses, identifying the communicating nodes is difficult when NATs addresses, identifying the communicating nodes is difficult when NATs
are employed because private address spaces are overlapping. In are employed because private address spaces are overlapping. In
other words, two hosts cannot be distinguished from each other solely other words, two hosts cannot be distinguished from each other solely
based on their IP address. With HIP, the transport-layer end-points based on their IP addresses. With HIP, the transport-layer endpoints
(i.e. applications) are bound to unique Host Identities rather than (i.e., applications) are bound to unique Host Identities rather than
overlapping private addresses. This allows two end-points to overlapping private addresses. This allows two endpoints to
distinguish one other even when they are located in different private distinguish one other even when they are located in different private
address realms. Thus, the IP addresses are used only for routing address realms. Thus, the IP addresses are used only for routing
purposes and can be changed freely by NATs when a packet between two purposes and can be changed freely by NATs when a packet between two
HIP capable hosts traverses through multiple private address realms. HIP-capable hosts traverses through multiple private address realms.
NAT traversal extensions for HIP [I-D.ietf-hip-native-nat-traversal] NAT traversal extensions for HIP [RFC9028] can be used to realize the
can be used to realize the actual end-to-end connectivity through NAT actual end-to-end connectivity through NAT devices. To support basic
devices. To support basic backward compatibility with legacy NATs, backward compatibility with legacy NATs, the extensions encapsulate
the extensions encapsulate both HIP control and data plane in UDP. both HIP control and data planes in UDP. The extensions define
The extensions define mechanisms for forwarding the two planes mechanisms for forwarding the two planes through an intermediary host
through an intermediary host called HIP relay and procedures to called HIP relay and procedures to establish direct end-to-end
establish direct end-to-end connectivity by penetrating NATs. connectivity by penetrating NATs. Besides this "native" NAT
Besides this "native" NAT traversal mode for HIP, other NAT traversal traversal mode for HIP, other NAT traversal mechanisms have been
mechanisms have been successfully utilized, such as Teredo [RFC4380] successfully utilized, such as Teredo [RFC4380] (as described in
(as described in further detail in [varjonen-split]). further detail in [varjonen-split]).
Besides legacy NATs, a HIP-aware NAT has been designed and Besides legacy NATs, a HIP-aware NAT has been designed and
implemented [ylitalo-spinat]. For a HIP-based flow, a HIP-aware NAT implemented [ylitalo-spinat]. For a HIP-based flow, a HIP-aware NAT
or NAT-PT system tracks the mapping of HITs, and the corresponding or HIP-aware historic NAT-PT system tracks the mapping of HITs, and
ESP SPIs, to an IP address. The NAT system has to learn mappings the corresponding ESP SPIs, to an IP address. The NAT system has to
both from HITs and from SPIs to IP addresses. Many HITs (and SPIs) learn mappings both from HITs and from SPIs to IP addresses. Many
can map to a single IP address on a NAT, simplifying connections on HITs (and SPIs) can map to a single IP address on a NAT, simplifying
address-poor NAT interfaces. The NAT can gain much of its knowledge connections on address-poor NAT interfaces. The NAT can gain much of
from the HIP packets themselves; however, some NAT configuration may its knowledge from the HIP packets themselves; however, some NAT
be necessary. configuration may be necessary.
8.1. HIP and Upper-layer checksums 8.1. HIP and Upper-Layer Checksums
There is no way for a host to know if any of the IP addresses in an There is no way for a host to know if any of the IP addresses in an
IP header are the addresses used to calculate the TCP checksum. That IP header are the addresses used to calculate the TCP checksum. That
is, it is not feasible to calculate the TCP checksum using the actual is, it is not feasible to calculate the TCP checksum using the actual
IP addresses in the pseudo header; the addresses received in the IP addresses in the pseudo header; the addresses received in the
incoming packet are not necessarily the same as they were on the incoming packet are not necessarily the same as they were on the
sending host. Furthermore, it is not possible to recompute the sending host. Furthermore, it is not possible to recompute the
upper-layer checksums in the NAT/NAT-PT system, since the traffic is upper-layer checksums in the NAT/NAT-PT system, since the traffic is
ESP protected. Consequently, the TCP and UDP checksums are ESP protected. Consequently, the TCP and UDP checksums are
calculated using the HITs in the place of the IP addresses in the calculated using the HITs in the place of the IP addresses in the
pseudo header. Furthermore, only the IPv6 pseudo header format is pseudo header. Furthermore, only the IPv6 pseudo header format is
used. This provides for IPv4 / IPv6 protocol translation. used. This provides for IPv4 / IPv6 protocol translation.
9. Multicast 9. Multicast
A number of studies investigating HIP-based multicast have been A number of studies investigating HIP-based multicast have been
published (including [shields-hip], [xueyong-hip], [xueyong-hip], published (including [shields-hip], [zhu-hip], [amir-hip],
[amir-hip], [kovacshazi-host] and [xueyong-secure]). In particular, [kovacshazi-host], and [zhu-secure]). In particular, so-called Bloom
so-called Bloom filters, that allow compressing of multiple labels filters, which allow the compression of multiple labels into small
into small data structures, may be a promising way forward data structures, may be a promising way forward [sarela-bloom].
[sarela-bloom]. However, the different schemes have not been adopted However, the different schemes have not been adopted by the HIP
by the HIP working group (nor the HIP research group in IRTF), so the working group (nor the HIP research group in the IRTF), so the
details are not further elaborated here. details are not further elaborated here.
10. HIP policies 10. HIP Policies
There are a number of variables that influence the HIP exchange that There are a number of variables that influence the HIP exchange that
each host must support. All HIP implementations should support at each host must support. All HIP implementations should support at
least 2 HIs, one to publish in DNS or similar directory service and least two HIs, one to publish in DNS or a similar directory service
an unpublished one for anonymous usage (that should expect to be and an unpublished one for anonymous usage (that should expect to be
rotated frequently in order to disrupt linkability/trackability). rotated frequently in order to disrupt linkability and/or
Although unpublished HIs will be rarely used as responder HIs, they trackability). Although unpublished HIs will rarely be used as
are likely to be common for initiators. As stated in [RFC7401], "all Responder HIs, they are likely to be common for Initiators. As
HIP implementations MUST support more than one simultaneous HI, at stated in [RFC7401], "all HIP implementations MUST support more than
least one of which SHOULD be reserved for anonymous usage", and one simultaneous HI, at least one of which SHOULD be reserved for
"support for more than two HIs is RECOMMENDED". This provides new anonymous usage", and "support for more than two HIs is RECOMMENDED".
challenges for systems or users to decide which type of HI to expose This provides new challenges for systems or users to decide which
when they start a new session. type of HI to expose when they start a new session.
Opportunistic mode (where the initiator starts a HIP exchange without Opportunistic mode (where the Initiator starts a HIP exchange without
prior knowledge of the responder's HI) presents a security tradeoff. prior knowledge of the Responder's HI) presents a security trade-off.
At the expense of being subject to MITM attacks, the opportunistic At the expense of being subject to MitM attacks, the opportunistic
mode allows the initiator to learn the identity of the responder mode allows the Initiator to learn the identity of the Responder
during communication rather than from an external directory. during communication rather than from an external directory.
Opportunistic mode can be used for registration to HIP-based services Opportunistic mode can be used for registration to HIP-based services
[RFC8003] (i.e. utilized by HIP for its own internal purposes) or by [RFC8003] (i.e., utilized by HIP for its own internal purposes) or by
the application layer [komu-leap]. For security reasons, especially the application layer [komu-leap]. For security reasons, especially
the latter requires some involvement from the user to accept the the latter requires some involvement from the user to accept the
identity of the responder similar to how SSH prompts the user when identity of the Responder similar to how the Secure Shell (SSH)
connecting to a server for the first time [pham-leap]. In practice, protocol prompts the user when connecting to a server for the first
this can be realized in end-host based firewalls in the case of time [pham-leap]. In practice, this can be realized in end-host-
legacy applications [karvonen-usable] or with native APIs for HIP based firewalls in the case of legacy applications [karvonen-usable]
APIs [RFC6317] in the case of HIP-aware applications. or with native APIs for HIP APIs [RFC6317] in the case of HIP-aware
applications.
As stated in [RFC7401], "Initiators MAY use a different HI for As stated in [RFC7401]:
different Responders to provide basic privacy. Whether such private
HIs are used repeatedly with the same Responder, and how long these
HIs are used, are decided by local policy and depend on the privacy
requirements of the Initiator".
According to [RFC7401], "Responders that only respond to selected | Initiators MAY use a different HI for different Responders to
Initiators require an Access Control List (ACL), representing for | provide basic privacy. Whether such private HIs are used
which hosts they accept HIP base exchanges, and the preferred | repeatedly with the same Responder, and how long these HIs are
transport format and local lifetimes. Wildcarding SHOULD be | used, are decided by local policy and depend on the privacy
supported for such ACLs, and also for Responders that offer public or | requirements of the Initiator.
anonymous services".
11. Security considerations According to [RFC7401]:
| Responders that only respond to selected Initiators require an
| Access Control List (ACL), representing for which hosts they
| accept HIP base exchanges, and the preferred transport format and
| local lifetimes. Wildcarding SHOULD be supported for such ACLs,
| and also for Responders that offer public or anonymous services.
11. Security Considerations
This section includes discussion on some issues and solutions related This section includes discussion on some issues and solutions related
to security in the HIP architecture. to security in the HIP architecture.
11.1. MiTM Attacks 11.1. MitM Attacks
HIP takes advantage of the Host Identity paradigm to provide secure HIP takes advantage of the Host Identity paradigm to provide secure
authentication of hosts and to provide a fast key exchange for ESP. authentication of hosts and to provide a fast key exchange for ESP.
HIP also attempts to limit the exposure of the host to various HIP also attempts to limit the exposure of the host to various
denial-of-service (DoS) and man-in-the-middle (MitM) attacks. In so denial-of-service (DoS) and man-in-the-middle (MitM) attacks. In so
doing, HIP itself is subject to its own DoS and MitM attacks that doing, HIP itself is subject to its own DoS and MitM attacks that
potentially could be more damaging to a host's ability to conduct potentially could be more damaging to a host's ability to conduct
business as usual. business as usual.
Resource exhausting denial-of-service attacks take advantage of the Resource exhausting DoS attacks take advantage of the cost of setting
cost of setting up a state for a protocol on the responder compared up a state for a protocol on the Responder compared to the
to the 'cheapness' on the initiator. HIP allows a responder to 'cheapness' on the Initiator. HIP allows a Responder to increase the
increase the cost of the start of state on the initiator and makes an cost of the start of state on the Initiator and makes an effort to
effort to reduce the cost to the responder. This is done by having reduce the cost to the Responder. This is done by having the
the responder start the authenticated Diffie-Hellman exchange instead Responder start the authenticated Diffie-Hellman exchange instead of
of the initiator, making the HIP base exchange 4 packets long. The the Initiator, making the HIP base exchange four packets long. The
first packet sent by the responder can be prebuilt to further first packet sent by the Responder can be prebuilt to further
mitigate the costs. This packet also includes a computational puzzle mitigate the costs. This packet also includes a computational puzzle
that can optionally be used to further delay the initiator, for that can optionally be used to further delay the Initiator, for
instance, when the responder is overloaded. The details are instance, when the Responder is overloaded. The details are
explained in the base exchange specification [RFC7401]. explained in the base exchange specification [RFC7401].
Man-in-the-middle (MitM) attacks are difficult to defend against, MitM attacks are difficult to defend against without third-party
without third-party authentication. A skillful MitM could easily authentication. A skillful MitM could easily handle all parts of the
handle all parts of the HIP base exchange, but HIP indirectly HIP base exchange, but HIP indirectly provides the following
provides the following protection from a MitM attack. If the protection from a MitM attack. If the Responder's HI is retrieved
responder's HI is retrieved from a signed DNS zone or securely from a signed DNS zone or securely obtained by some other means, the
obtained by some other means, the initiator can use this to Initiator can use this to authenticate the signed HIP packets.
authenticate the signed HIP packets. Likewise, if the initiator's HI Likewise, if the Initiator's HI is in a secure DNS zone, the
is in a secure DNS zone, the responder can retrieve it and validate Responder can retrieve it and validate the signed HIP packets.
the signed HIP packets. However, since an initiator may choose to However, since an Initiator may choose to use an unpublished HI, it
use an unpublished HI, it knowingly risks a MitM attack. The knowingly risks a MitM attack. The Responder may choose not to
responder may choose not to accept a HIP exchange with an initiator accept a HIP exchange with an Initiator using an unknown HI.
using an unknown HI.
Other types of MitM attacks against HIP can be mounted using ICMP Other types of MitM attacks against HIP can be mounted using ICMP
messages that can be used to signal about problems. As an overall messages that can be used to signal about problems. As an overall
guideline, the ICMP messages should be considered as unreliable guideline, the ICMP messages should be considered as unreliable
"hints" and should be acted upon only after timeouts. The exact "hints" and should be acted upon only after timeouts. The exact
attack scenarios and countermeasures are described in full detail the attack scenarios and countermeasures are described in full detail in
base exchange specification [RFC7401]. the base exchange specification [RFC7401].
A MitM attacker could try to replay older I1 or R1 messages using A MitM attacker could try to replay older I1 or R1 messages using
weaker cryptographic algorithms as described in section 4.1.4 in weaker cryptographic algorithms as described in Section 4.1.4 of
[RFC7401]. The base exchange has been augmented to deal with such an [RFC7401]. The base exchange has been augmented to deal with such an
attack by restarting on detecting the attack. At worst this would attack by restarting on the detection of the attack. At worst, this
only lead to a situation in which the base exchange would never would only lead to a situation in which the base exchange would never
finish (or would be aborted after some retries). As a drawback, this finish (or would be aborted after some retries). As a drawback, this
leads to a 6-way base exchange which may seem bad at first. However, leads to a six-way base exchange, which may seem bad at first.
since this only occurs in an attack scenario and since the attack can However, since this only occurs in an attack scenario and since the
be handled (so it is not interesting to mount anymore), we assume the attack can be handled (so it is not interesting to mount anymore), we
subsequent messages do not represent a security threat. Since the assume the subsequent messages do not represent a security threat.
MitM cannot be successful with a downgrade attack, these sorts of Since the MitM cannot be successful with a downgrade attack, these
attacks will only occur as 'nuisance' attacks. So, the base exchange sorts of attacks will only occur as 'nuisance' attacks. So, the base
would still be usually just four packets even though implementations exchange would still be usually just four packets even though
must be prepared to protect themselves against the downgrade attack. implementations must be prepared to protect themselves against the
downgrade attack.
In HIP, the Security Association for ESP is indexed by the SPI; the In HIP, the Security Association for ESP is indexed by the SPI; the
source address is always ignored, and the destination address may be source address is always ignored, and the destination address may be
ignored as well. Therefore, HIP-enabled Encapsulated Security ignored as well. Therefore, HIP-enabled ESP is IP address
Payload (ESP) is IP address independent. This might seem to make independent. This might seem to make attacking easier, but ESP with
attacking easier, but ESP with replay protection is already as well replay protection is already as well protected as possible, and the
protected as possible, and the removal of the IP address as a check removal of the IP address as a check should not increase the exposure
should not increase the exposure of ESP to DoS attacks. of ESP to DoS attacks.
11.2. Protection against flooding attacks 11.2. Protection against Flooding Attacks
Although the idea of informing about address changes by simply Although the idea of informing about address changes by simply
sending packets with a new source address appears appealing, it is sending packets with a new source address appears appealing, it is
not secure enough. That is, even if HIP does not rely on the source not secure enough. That is, even if HIP does not rely on the source
address for anything (once the base exchange has been completed), it address for anything (once the base exchange has been completed), it
appears to be necessary to check a mobile node's reachability at the appears to be necessary to check a mobile node's reachability at the
new address before actually sending any larger amounts of traffic to new address before actually sending any larger amounts of traffic to
the new address. the new address.
Blindly accepting new addresses would potentially lead to flooding Blindly accepting new addresses would potentially lead to flooding
Denial-of-Service attacks against third parties [RFC4225]. In a DoS attacks against third parties [RFC4225]. In a distributed
distributed flooding attack an attacker opens high volume HIP flooding attack, an attacker opens high-volume HIP connections with a
connections with a large number of hosts (using unpublished HIs), and large number of hosts (using unpublished HIs) and then claims to all
then claims to all of these hosts that it has moved to a target of these hosts that it has moved to a target node's IP address. If
node's IP address. If the peer hosts were to simply accept the move, the peer hosts were to simply accept the move, the result would be a
the result would be a packet flood to the target node's address. To packet flood to the target node's address. To prevent this type of
prevent this type of attack, HIP mobility extensions include a return attack, HIP mobility extensions include a return routability check
routability check procedure where the reachability of a node is procedure where the reachability of a node is separately checked at
separately checked at each address before using the address for each address before using the address for larger amounts of traffic.
larger amounts of traffic.
A credit-based authorization approach for host mobility with the Host A credit-based authorization approach for "Host Mobility with the
Identity Protocol [RFC8046] can be used between hosts for sending Host Identity Protocol" [RFC8046] can be used between hosts for
data prior to completing the address tests. Otherwise, if HIP is sending data prior to completing the address tests. Otherwise, if
used between two hosts that fully trust each other, the hosts may HIP is used between two hosts that fully trust each other, the hosts
optionally decide to skip the address tests. However, such may optionally decide to skip the address tests. However, such
performance optimization must be restricted to peers that are known performance optimization must be restricted to peers that are known
to be trustworthy and capable of protecting themselves from malicious to be trustworthy and capable of protecting themselves from malicious
software. software.
11.3. HITs used in ACLs 11.3. HITs Used in ACLs
At end-hosts, HITs can be used in IP-based access control lists at At end-hosts, HITs can be used in IP-based access control lists at
the application and network layers. At middleboxes, HIP-aware the application and network layers. At middleboxes, HIP-aware
firewalls [lindqvist-enterprise] can use HITs or public keys to firewalls [lindqvist-enterprise] can use HITs or public keys to
control both ingress and egress access to networks or individual control both ingress and egress access to networks or individual
hosts, even in the presence of mobile devices because the HITs and hosts, even in the presence of mobile devices because the HITs and
public keys are topology independent. As discussed earlier in public keys are topology independent. As discussed earlier in
Section 7, once a HIP session has been established, the SPI value in Section 7, once a HIP session has been established, the SPI value in
an ESP packet may be used as an index, indicating the HITs. In an ESP packet may be used as an index, indicating the HITs. In
practice, firewalls can inspect HIP packets to learn of the bindings practice, firewalls can inspect HIP packets to learn of the bindings
between HITs, SPI values, and IP addresses. They can even explicitly between HITs, SPI values, and IP addresses. They can even explicitly
control ESP usage, dynamically opening ESP only for specific SPI control ESP usage, dynamically opening ESP only for specific SPI
values and IP addresses. The signatures in HIP packets allow a values and IP addresses. The signatures in HIP packets allow a
capable firewall to ensure that the HIP exchange is indeed occurring capable firewall to ensure that the HIP exchange is indeed occurring
between two known hosts. This may increase firewall security. between two known hosts. This may increase firewall security.
A potential drawback of HITs in ACLs is their 'flatness' means they A potential drawback of HITs in ACLs is their 'flatness', which means
cannot be aggregated, and this could potentially result in larger they cannot be aggregated, and this could potentially result in
table searches in HIP-aware firewalls. A way to optimize this could larger table searches in HIP-aware firewalls. A way to optimize this
be to utilize Bloom filters for grouping of HITs [sarela-bloom]. could be to utilize Bloom filters for grouping HITs [sarela-bloom].
However, it should be noted that it is also easier to exclude However, it should be noted that it is also easier to exclude
individual, misbehaving hosts out when the firewall rules concern individual, misbehaving hosts when the firewall rules concern
individual HITs rather than groups. individual HITs rather than groups.
There has been considerable bad experience with distributed ACLs that There has been considerable bad experience with distributed ACLs that
contain public key related material, for example, with SSH. If the contain material related to public keys, for example, with SSH. If
owner of a key needs to revoke it for any reason, the task of finding the owner of a key needs to revoke it for any reason, the task of
all locations where the key is held in an ACL may be impossible. If finding all locations where the key is held in an ACL may be
the reason for the revocation is due to private key theft, this could impossible. If the reason for the revocation is due to private key
be a serious issue. theft, this could be a serious issue.
A host can keep track of all of its partners that might use its HIT A host can keep track of all of its partners that might use its HIT
in an ACL by logging all remote HITs. It should only be necessary to in an ACL by logging all remote HITs. It should only be necessary to
log responder hosts. With this information, the host can notify the log Responder hosts. With this information, the host can notify the
various hosts about the change to the HIT. There have been attempts various hosts about the change to the HIT. There have been attempts
to develop a secure method to issue the HIT revocation notice to develop a secure method to issue the HIT revocation notice
[zhang-revocation]. [zhang-revocation].
Some of the HIP-aware middleboxes, such as firewalls Some of the HIP-aware middleboxes, such as firewalls
[lindqvist-enterprise] or NATs [ylitalo-spinat], may observe the on- [lindqvist-enterprise] or NATs [ylitalo-spinat], may observe the on-
path traffic passively. Such middleboxes are transparent by their path traffic passively. Such middleboxes are transparent by their
nature and may not get a notification when a host moves to a nature and may not get a notification when a host moves to a
different network. Thus, such middleboxes should maintain soft state different network. Thus, such middleboxes should maintain soft state
and timeout when the control and data plane between two HIP end-hosts and time out when the control and data planes between two HIP end-
has been idle too long. Correspondingly, the two end-hosts may send hosts have been idle too long. Correspondingly, the two end-hosts
periodically keepalives, such as UPDATE packets or ICMP messages may send periodically keepalives, such as UPDATE packets or ICMP
inside the ESP tunnel, to sustain state at the on-path middleboxes. messages inside the ESP tunnel, to sustain state at the on-path
middleboxes.
One general limitation related to end-to-end encryption is that One general limitation related to end-to-end encryption is that
middleboxes may not be able to participate to the protection of data middleboxes may not be able to participate in the protection of data
flows. While the issue may affect also other protocols, Heer at al flows. While the issue may also affect other protocols, Heer et al.
[heer-end-host] have analyzed the problem in the context of HIP. [heer-end-host] have analyzed the problem in the context of HIP.
More specifically, when ESP is used as the data-plane protocol for More specifically, when ESP is used as the data plane protocol for
HIP, the association between the control and data plane is weak and HIP, the association between the control and data planes is weak and
can be exploited under certain assumptions. In the scenario, the can be exploited under certain assumptions. In the scenario, the
attacker has already gained access to the target network protected by attacker has already gained access to the target network protected by
a HIP-aware firewall, but wants to circumvent the HIP-based firewall. a HIP-aware firewall, but wants to circumvent the HIP-based firewall.
To achieve this, the attacker passively observes a base exchange To achieve this, the attacker passively observes a base exchange
between two HIP hosts and later replays it. This way, the attacker between two HIP hosts and later replays it. This way, the attacker
manages to penetrate the firewall and can use a fake ESP tunnel to manages to penetrate the firewall and can use a fake ESP tunnel to
transport its own data. This is possible because the firewall cannot transport its own data. This is possible because the firewall cannot
distinguish when the ESP tunnel is valid. As a solution, HIP-aware distinguish when the ESP tunnel is valid. As a solution, HIP-aware
middleboxes may participate to the control plane interaction by middleboxes may participate in the control plane interaction by
adding random nonce parameters to the control traffic, which the end- adding random nonce parameters to the control traffic, which the end-
hosts have to sign to guarantee the freshness of the control traffic hosts have to sign to guarantee the freshness of the control traffic
[heer-midauth]. As an alternative, extensions for transporting data [heer-midauth]. As an alternative, extensions for transporting the
plane directly over the control plane can be used [RFC6078]. data plane directly over the control plane can be used [RFC6078].
11.4. Alternative HI considerations 11.4. Alternative HI Considerations
The definition of the Host Identifier states that the HI need not be The definition of the Host Identifier states that the HI need not be
a public key. It implies that the HI could be any value; for example a public key. It implies that the HI could be any value, for
a FQDN. This document does not describe how to support such a non- example, a FQDN. This document does not describe how to support such
cryptographic HI, but examples of such protocol variants do exist a non-cryptographic HI, but examples of such protocol variants do
([urien-rfid], [urien-rfid-draft]). A non-cryptographic HI would exist ([urien-rfid], [urien-rfid-draft]). A non-cryptographic HI
still offer the services of the HIT or LSI for NAT traversal. It would still offer the services of the HIT or LSI for NAT traversal.
would be possible to carry HITs in HIP packets that had neither It would be possible to carry HITs in HIP packets that had neither
privacy nor authentication. Such schemes may be employed for privacy nor authentication. Such schemes may be employed for
resource constrained devices, such as small sensors operating on resource-constrained devices, such as small sensors operating on
battery power, but are not further analyzed here. battery power, but are not further analyzed here.
If it is desirable to use HIP in a low security situation where If it is desirable to use HIP in a low-security situation where
public key computations are considered expensive, HIP can be used public key computations are considered expensive, HIP can be used
with very short Diffie-Hellman and Host Identity keys. Such use with very short Diffie-Hellman and Host Identity keys. Such use
makes the participating hosts vulnerable to MitM and connection makes the participating hosts vulnerable to MitM and connection
hijacking attacks. However, it does not cause flooding dangers, hijacking attacks. However, it does not cause flooding dangers,
since the address check mechanism relies on the routing system and since the address check mechanism relies on the routing system and
not on cryptographic strength. not on cryptographic strength.
11.5. Trust On First Use 11.5. Trust on First Use
[RFC7435] highlights four design principles for Leap of Faith, or [RFC7435] highlights four design principles for Leap of Faith, or
Trust On First Use (TOFU), protocols that apply also to opportunistic Trust On First Use (TOFU), protocols that apply also to opportunistic
HIP: HIP:
1. Coexist with explicit policy 1. Coexist with explicit policy
2. Prioritize communication 2. Prioritize communication
3. Maximize security peer by peer 3. Maximize security peer by peer
4. No misrepresentation of security 4. No misrepresentation of security
According to the first TOFU design principle, "opportunistic security According to the first TOFU design principle, "Opportunistic security
never displaces or preempts explicit policy". Some application data never displaces or preempts explicit policy". Some application data
may be too sensitive, so the related policy could require may be too sensitive, so the related policy could require
authentication (i.e, the public key or certificate) in such a case authentication (i.e., the public key or certificate) in such a case
instead of the unauthenticated opportunistic mode. In practice, this instead of the unauthenticated opportunistic mode. In practice, this
has been realized in HIP implementations as follows [RFC6538]. has been realized in HIP implementations as follows [RFC6538].
The OpenHIP implementation allowed an Initiator to use opportunistic The OpenHIP implementation allowed an Initiator to use opportunistic
mode only with an explicitly configured Responder IP address, when mode only with an explicitly configured Responder IP address, when
the Responder's HIT is unknown. At the Responder, OpenHIP had an the Responder's HIT is unknown. At the Responder, OpenHIP had an
option to allow opportunistic mode with any Initiator -- trust any option to allow opportunistic mode with any Initiator -- trust any
Initiator. Initiator.
HIP for Linux (HIPL) developers experimented with more fine-grained HIP for Linux (HIPL) developers experimented with more fine-grained
policies operating at the application level. HIPL implementation policies operating at the application level. The HIPL implementation
utilized so called "LD_PRELOAD" hooking at the application layer that utilized so-called "LD_PRELOAD" hooking at the application layer that
allowed a dynamically linked library to intercept socket-related allowed a dynamically linked library to intercept socket-related
calls without rebuilding the related application binaries. The calls without rebuilding the related application binaries. The
library acted as a shim layer between the application and transport library acted as a shim layer between the application and transport
layers. The shim layer translated the non-HIP based socket calls layers. The shim layer translated the non-HIP-based socket calls
from the application into HIP-based socket calls. While the shim from the application into HIP-based socket calls. While the shim
library involved some level of complexity as described in more detail library involved some level of complexity as described in more detail
in [komu-leap], it achieved the goal of applying opportunistic mode in [komu-leap], it achieved the goal of applying opportunistic mode
at the granularity of individual applications. at the granularity of individual applications.
The second TOFU principle essentially states that communication The second TOFU principle essentially states that communication
should be first class citizen instead of security. So opportunistic should prioritized over security. So opportunistic mode should be,
mode should be, in general, allowed even if no authentication is in general, allowed even if no authentication is present, and even
present, and even possibly a fallback to non-encrypted communications possibly a fallback to unencrypted communications could be allowed
could be allowed (if policy permits) instead of blocking (if policy permits) instead of blocking communications. In practice,
communications. In practice, this can be realized in three steps. this can be realized in three steps. In the first step, a HIP
In the first step, a HIP Initiator can look up the HI of a Responder Initiator can look up the HI of a Responder from a directory such as
from a directory such as DNS. When the Initiator discovers a HI, it DNS. When the Initiator discovers a HI, it can use the HI for
can use the HI for authentication and skip the rest of the following authentication and skip the rest of the following steps. In the
steps. In the second step, the Initiator can, upon failing to find a second step, the Initiator can, upon failing to find a HI, try
HI, try opportunistic mode with the Responder. In the third step, opportunistic mode with the Responder. In the third step, the
the Initiator can fall back to non-HIP based communications upon Initiator can fall back to non-HIP-based communications upon failing
failing with opportunistic mode if the policy allows it. This three with opportunistic mode if the policy allows it. This three-step
step model has been implemented successfully and described in more model has been implemented successfully and described in more detail
detail in [komu-leap]. in [komu-leap].
The third TOFU principle suggests that security should be maximized, The third TOFU principle suggests that security should be maximized,
so that at least opportunistic security would be employed. The three so that at least opportunistic security would be employed. The
step model described earlier prefers authentication when it is three-step model described earlier prefers authentication when it is
available, e.g., via DNS records (and possibly even via DNSSEC when available, e.g., via DNS records (and possibly even via DNSSEC when
available) and falls back to opportunistic mode when no out-of-band available) and falls back to opportunistic mode when no out-of-band
credentials are available. As the last resort, fallback to non-HIP credentials are available. As the last resort, fallback to non-HIP-
based communications can be used if the policy allows it. Also, based communications can be used if the policy allows it. Also,
since perfect forward security (PFS) is explicitly mentioned in the since perfect forward secrecy (PFS) is explicitly mentioned in the
third design principle, it is worth mentioning that HIP supports it. third design principle, it is worth mentioning that HIP supports it.
The fourth TOFU principle states that users and non-interactive The fourth TOFU principle states that users and noninteractive
applications should be properly informed about the level of security applications should be properly informed about the level of security
being applied. In practice, non-HIP aware applications would assume being applied. In practice, non-HIP-aware applications would assume
no extra security being applied, so misleading at least a non- that no extra security is being applied, so misleading at least a
interactive application should not be possible. In the case of noninteractive application should not be possible. In the case of
interactive desktop applications, system-level prompts have been interactive desktop applications, system-level prompts have been
utilized in earlier HIP experiments [karvonen-usable], [RFC6538] to utilized in earlier HIP experiments [karvonen-usable] [RFC6538] to
guide the user about the underlying HIP-based security. In general, guide the user about the underlying HIP-based security. In general,
users in those experiments perceived when HIP-based security was users in those experiments perceived when HIP-based security was
being used versus not used. However, the users failed to notice the being used versus not used. However, the users failed to notice the
difference between opportunistic and non-opportunistic HIP. The difference between opportunistic, non-authenticated HIP and non-
reason for this was that the opportunistic HIP (i.e. lowered level of opportunistic, authenticated HIP. The reason for this was that the
security) was not clearly indicated in the prompt. This provided a opportunistic HIP (i.e., lowered level of security) was not clearly
valuable lesson to further improve the user interface. indicated in the prompt. This provided a valuable lesson to further
improve the user interface.
In the case of HIP-aware applications, native sockets APIs for HIP as In the case of HIP-aware applications, native sockets APIs for HIP as
specified in [RFC6317] can be used to develop application-specific specified in [RFC6317] can be used to develop application-specific
logic instead of using generic system-level prompting. In such case, logic instead of using generic system-level prompting. In such a
the application itself can directly prompt the user or otherwise case, the application itself can directly prompt the user or
manage the situation in other ways. In this case, also non- otherwise manage the situation in other ways. In this case,
interactive applications can properly log the level of security being noninteractive applications also can properly log the level of
employed because the developer can now explicitly program the use of security being employed because the developer can now explicitly
authenticated HIP, opportunistic HIP and plain-text communication. program the use of authenticated HIP, opportunistic HIP, and plain-
text communication.
It is worth mentioning a few additional items discussed in [RFC7435]. It is worth mentioning a few additional items discussed in [RFC7435].
Related to active attacks, HIP has built-in protection against Related to active attacks, HIP has built-in protection against
cipher-suite down-grade attacks as described in detail in [RFC7401]. ciphersuite downgrade attacks as described in detail in [RFC7401].
In addition, pre-deployed certificates could be used to mitigate In addition, pre-deployed certificates could be used to mitigate
against active attacks in the case of opportunistic mode as mentioned against active attacks in the case of opportunistic mode as mentioned
in [RFC6538]. in [RFC6538].
Detection of peer capabilities is also mentioned in the TOFU context. Detection of peer capabilities is also mentioned in the TOFU context.
As discussed in this section, the three-step model can be used to As discussed in this section, the three-step model can be used to
detect peer capabilities. A host can achieve the first step of detect peer capabilities. A host can achieve the first step of
authentication, i.e., discovery of a public key, via DNS, for authentication, i.e., discovery of a public key, via DNS, for
instance. If the host found no keys, the host can then try instance. If the host finds no keys, the host can then try
opportunistic mode as the second step. Upon a timeout, the host can opportunistic mode as the second step. Upon a timeout, the host can
then proceed to the third step by falling back to non-HIP based then proceed to the third step by falling back to non-HIP-based
communications if the policy permits. This last step is based on an communications if the policy permits. This last step is based on an
implicit timeout rather an explicit (negative) acknowledgment like in implicit timeout rather an explicit (negative) acknowledgment like in
the case of DNS, so the user may conclude prematurely that the the case of DNS, so the user may conclude prematurely that the
connectivity has failed. To speed up the detection phase by connectivity has failed. To speed up the detection phase by
explicitly detecting if the peer supports opportunistic HIP, explicitly detecting if the peer supports opportunistic HIP,
researchers have proposed TCP specific extensions [RFC6538], researchers have proposed TCP-specific extensions [RFC6538]
[komu-leap]. In a nutshell, an Initiator sends simultaneously both [komu-leap]. In a nutshell, an Initiator sends simultaneously both
an opportunistic I1 packet and the related TCP SYN datagram equipped an opportunistic I1 packet and the related TCP SYN datagram equipped
with a special TCP option to a peer. If the peer supports HIP, it with a special TCP option to a peer. If the peer supports HIP, it
drops the SYN packet and responds with an R1. If the peer is HIP drops the SYN packet and responds with an R1. If the peer is HIP
incapable, it drops the HIP packet (and the unknown TCP option) and incapable, it drops the HIP packet (and the unknown TCP option) and
responds with a TCP SYN-ACK. The benefit of the proposed scheme is responds with a TCP SYN-ACK. The benefit of the proposed scheme is a
faster, one round-trip fallback to non-HIP based communications. The faster, one round-trip fallback to non-HIP-based communications. The
drawback is that the approach is tied to TCP (IP-options were also drawback is that the approach is tied to TCP (IP options were also
considered, but do not work well with firewalls and NATs). considered, but do not work well with firewalls and NATs).
Naturally, the approach does not work against active attacker, but Naturally, the approach does not work against an active attacker, but
opportunistic mode is not anyway supposed to protect against such an opportunistic mode is not supposed to protect against such an
adversary. adversary anyway.
It is worth noting that while the use of opportunistic mode has some It is worth noting that while the use of opportunistic mode has some
benefits related to incremental deployment, it does not achieve all benefits related to incremental deployment, it does not achieve all
the benefits of authenticated HIP [komu-diss]. Namely, authenticated the benefits of authenticated HIP [komu-diss]. Namely, authenticated
HIP supports persistent identifiers in the sense that hosts are HIP supports persistent identifiers in the sense that hosts are
identified with the same HI independently of their movement. identified with the same HI independent of their movement.
Opportunistic HIP meets this goal only partially: after the first Opportunistic HIP meets this goal only partially: after the first
contact between two hosts, HIP can successfully sustain connectivity contact between two hosts, HIP can successfully sustain connectivity
with its mobility management extensions, but problems emerge when the with its mobility management extensions, but problems emerge when the
hosts close the HIP association and try to re-establish connectivity. hosts close the HIP association and try to reestablish connectivity.
As hosts can change their location, it is no longer guaranteed that As hosts can change their location, it is no longer guaranteed that
the same IP address belongs to the same host. The same address can the same IP address belongs to the same host. The same address can
be temporally assigned to different hosts, e.g., due to the reuse of be temporally assigned to different hosts, e.g., due to the reuse of
IP addresses (e.g., by a DHCP service), overlapping private address IP addresses (e.g., by a DHCP service), the overlapping of private
realms (see also the discussion on Internet transparency in address realms (see also the discussion on Internet transparency in
Appendix A.1) or due to an attempted attack. Appendix A.1), or due to an attempted attack.
12. IANA considerations
This document has no actions for IANA.
13. Acknowledgments
For the people historically involved in the early stages of HIP, see
the Acknowledgments section in the Host Identity Protocol
specification.
During the later stages of this document, when the editing baton was
transferred to Pekka Nikander, the comments from the early
implementers and others, including Jari Arkko, Jeff AhrenHolz, Tom
Henderson, Petri Jokela, Miika Komu, Mika Kousa, Andrew McGregor, Jan
Melen, Tim Shepard, Jukka Ylitalo, Sasu Tarkoma, and Jorma Wall, were
invaluable. Also, the comments from Lars Eggert, Spencer Dawkins,
Dave Crocker and Erik Giesa were also useful.
The authors want to express their special thanks to Tom Henderson,
who took the burden of editing the document in response to IESG
comments at the time when both of the authors were busy doing other
things. Without his perseverance original document might have never
made it as RFC4423.
This main effort to update and move HIP forward within the IETF 12. IANA Considerations
process owes its impetuous to a number of HIP development teams. The
authors are grateful for Boeing, Helsinki Institute for Information
Technology (HIIT), NomadicLab of Ericsson, and the three
universities: RWTH Aachen, Aalto and University of Helsinki, for
their efforts. Without their collective efforts HIP would have
withered as on the IETF vine as a nice concept.
Thanks also for Suvi Koskinen for her help with proofreading and with This document has no IANA actions.
the reference jungle.
14. Changes from RFC 4423 13. Changes from RFC 4423
In a nutshell, the changes from RFC 4423 [RFC4423] are mostly In a nutshell, the changes from RFC 4423 [RFC4423] are mostly
editorial, including clarifications on topics described in a editorial, including clarifications on topics described in a
difficult way and omitting some of the non-architectural difficult way and omitting some of the non-architectural
(implementation) details that are already described in other (implementation) details that are already described in other
documents. A number of missing references to the literature were documents. A number of missing references to the literature were
also added. New topics include the drawbacks of HIP, discussion on also added. New topics include the drawbacks of HIP, a discussion on
802.15.4 and MAC security, HIP for IoT scenarios, deployment 802.15.4 and MAC security, HIP for IoT scenarios, deployment
considerations and description of the base exchange. considerations, and a description of the base exchange.
15. References
15.1. Normative References
[I-D.ietf-hip-dex] 14. References
Moskowitz, R. and R. Hummen, "HIP Diet EXchange (DEX)",
draft-ietf-hip-dex-06 (work in progress), December 2017.
[I-D.ietf-hip-native-nat-traversal] 14.1. Normative References
Keranen, A., Melen, J., and M. Komu, "Native NAT Traversal
Mode for the Host Identity Protocol", draft-ietf-hip-
native-nat-traversal-28 (work in progress), March 2018.
[RFC5482] Eggert, L. and F. Gont, "TCP User Timeout Option", [RFC5482] Eggert, L. and F. Gont, "TCP User Timeout Option",
RFC 5482, DOI 10.17487/RFC5482, March 2009, RFC 5482, DOI 10.17487/RFC5482, March 2009,
<https://www.rfc-editor.org/info/rfc5482>. <https://www.rfc-editor.org/info/rfc5482>.
[RFC6079] Camarillo, G., Nikander, P., Hautakorpi, J., Keranen, A., [RFC6079] Camarillo, G., Nikander, P., Hautakorpi, J., Keranen, A.,
and A. Johnston, "HIP BONE: Host Identity Protocol (HIP) and A. Johnston, "HIP BONE: Host Identity Protocol (HIP)
Based Overlay Networking Environment (BONE)", RFC 6079, Based Overlay Networking Environment (BONE)", RFC 6079,
DOI 10.17487/RFC6079, January 2011, <https://www.rfc- DOI 10.17487/RFC6079, January 2011,
editor.org/info/rfc6079>. <https://www.rfc-editor.org/info/rfc6079>.
[RFC7086] Keranen, A., Camarillo, G., and J. Maenpaa, "Host Identity [RFC7086] Keranen, A., Camarillo, G., and J. Maenpaa, "Host Identity
Protocol-Based Overlay Networking Environment (HIP BONE) Protocol-Based Overlay Networking Environment (HIP BONE)
Instance Specification for REsource LOcation And Discovery Instance Specification for REsource LOcation And Discovery
(RELOAD)", RFC 7086, DOI 10.17487/RFC7086, January 2014, (RELOAD)", RFC 7086, DOI 10.17487/RFC7086, January 2014,
<https://www.rfc-editor.org/info/rfc7086>. <https://www.rfc-editor.org/info/rfc7086>.
[RFC7343] Laganier, J. and F. Dupont, "An IPv6 Prefix for Overlay [RFC7343] Laganier, J. and F. Dupont, "An IPv6 Prefix for Overlay
Routable Cryptographic Hash Identifiers Version 2 Routable Cryptographic Hash Identifiers Version 2
(ORCHIDv2)", RFC 7343, DOI 10.17487/RFC7343, September (ORCHIDv2)", RFC 7343, DOI 10.17487/RFC7343, September
2014, <https://www.rfc-editor.org/info/rfc7343>. 2014, <https://www.rfc-editor.org/info/rfc7343>.
[RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T. [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
Henderson, "Host Identity Protocol Version 2 (HIPv2)", Henderson, "Host Identity Protocol Version 2 (HIPv2)",
RFC 7401, DOI 10.17487/RFC7401, April 2015, RFC 7401, DOI 10.17487/RFC7401, April 2015,
<https://www.rfc-editor.org/info/rfc7401>. <https://www.rfc-editor.org/info/rfc7401>.
[RFC7402] Jokela, P., Moskowitz, R., and J. Melen, "Using the [RFC7402] Jokela, P., Moskowitz, R., and J. Melen, "Using the
Encapsulating Security Payload (ESP) Transport Format with Encapsulating Security Payload (ESP) Transport Format with
the Host Identity Protocol (HIP)", RFC 7402, the Host Identity Protocol (HIP)", RFC 7402,
DOI 10.17487/RFC7402, April 2015, <https://www.rfc- DOI 10.17487/RFC7402, April 2015,
editor.org/info/rfc7402>. <https://www.rfc-editor.org/info/rfc7402>.
[RFC8002] Heer, T. and S. Varjonen, "Host Identity Protocol [RFC8002] Heer, T. and S. Varjonen, "Host Identity Protocol
Certificates", RFC 8002, DOI 10.17487/RFC8002, October Certificates", RFC 8002, DOI 10.17487/RFC8002, October
2016, <https://www.rfc-editor.org/info/rfc8002>. 2016, <https://www.rfc-editor.org/info/rfc8002>.
[RFC8003] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) [RFC8003] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Registration Extension", RFC 8003, DOI 10.17487/RFC8003, Registration Extension", RFC 8003, DOI 10.17487/RFC8003,
October 2016, <https://www.rfc-editor.org/info/rfc8003>. October 2016, <https://www.rfc-editor.org/info/rfc8003>.
[RFC8004] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) [RFC8004] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004, Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004,
October 2016, <https://www.rfc-editor.org/info/rfc8004>. October 2016, <https://www.rfc-editor.org/info/rfc8004>.
[RFC8005] Laganier, J., "Host Identity Protocol (HIP) Domain Name [RFC8005] Laganier, J., "Host Identity Protocol (HIP) Domain Name
System (DNS) Extension", RFC 8005, DOI 10.17487/RFC8005, System (DNS) Extension", RFC 8005, DOI 10.17487/RFC8005,
October 2016, <https://www.rfc-editor.org/info/rfc8005>. October 2016, <https://www.rfc-editor.org/info/rfc8005>.
[RFC8046] Henderson, T., Ed., Vogt, C., and J. Arkko, "Host Mobility [RFC8046] Henderson, T., Ed., Vogt, C., and J. Arkko, "Host Mobility
with the Host Identity Protocol", RFC 8046, with the Host Identity Protocol", RFC 8046,
DOI 10.17487/RFC8046, February 2017, <https://www.rfc- DOI 10.17487/RFC8046, February 2017,
editor.org/info/rfc8046>. <https://www.rfc-editor.org/info/rfc8046>.
[RFC8047] Henderson, T., Ed., Vogt, C., and J. Arkko, "Host [RFC8047] Henderson, T., Ed., Vogt, C., and J. Arkko, "Host
Multihoming with the Host Identity Protocol", RFC 8047, Multihoming with the Host Identity Protocol", RFC 8047,
DOI 10.17487/RFC8047, February 2017, <https://www.rfc- DOI 10.17487/RFC8047, February 2017,
editor.org/info/rfc8047>. <https://www.rfc-editor.org/info/rfc8047>.
15.2. Informative references [RFC9028] Keränen, A., Melén, J., and M. Komu, Ed., "Native NAT
Traversal Mode for the Host Identity Protocol", RFC 9028,
DOI 10.17487/RFC9028, July 2021,
<https://www.rfc-editor.org/info/rfc9028>.
[amir-hip] 14.2. Informative References
Amir, K., Forsgren, H., Grahn, K., Karvi, T., and G.
[amir-hip] Amir, K., Forsgren, H., Grahn, K., Karvi, T., and G.
Pulkkis, "Security and Trust of Public Key Cryptography Pulkkis, "Security and Trust of Public Key Cryptography
for HIP and HIP Multicast", International Journal of for HIP and HIP Multicast", International Journal of
Dependable and Trustworthy Information Systems (IJDTIS), Dependable and Trustworthy Information Systems (IJDTIS),
2(3), 17-35, DOI: 10.4018/jdtis.2011070102, 2013. Vol. 2, Issue 3, pp. 17-35, DOI 10.4018/jdtis.2011070102,
2013, <https://doi.org/10.4018/jdtis.2011070102>.
[aura-dos] [aura-dos] Aura, T., Nikander, P., and J. Leiwo, "DOS-Resistant
Aura, T., Nikander, P., and J. Leiwo, "DOS-resistant
Authentication with Client Puzzles", 8th International Authentication with Client Puzzles", 8th International
Workshop on Security Protocols, pages 170-177. Springer, , Workshop on Security Protocols, Security Protocols 2000,
April 2001. Lecture Notes in Computer Science, Vol. 2133, pp. 170-177,
Springer, DOI 10.1007/3-540-44810-1_22, September 2001,
<https://doi.org/10.1007/3-540-44810-1_22>.
[beal-dos] [beal-dos] Beal, J. and T. Shepard, "Deamplification of DoS Attacks
Beal, J. and T. Shephard, "Deamplification of DoS Attacks via Puzzles", October 2004.
via Puzzles", , October 2004.
[camarillo-p2psip] [camarillo-p2psip]
Camarillo, G., Maeenpaeae, J., Keraenen, A., and V. Camarillo, G., Mäenpää, J., Keränen, A., and V. Anderson,
Anderson, "Reducing delays related to NAT traversal in "Reducing delays related to NAT traversal in P2PSIP
P2PSIP session establishments", IEEE Consumer session establishments", IEEE Consumer Communications and
Communications and Networking Conference (CCNC), pp. Networking Conference (CCNC), pp. 549-553,
549-553 DOI: 10.1109/CCNC.2011.5766540, 2011. DOI 10.1109/CCNC.2011.5766540, 2011,
<https://doi.org/10.1109/CCNC.2011.5766540>.
[chiappa-endpoints] [chiappa-endpoints]
Chiappa, J., "Endpoints and Endpoint Names: A Proposed Chiappa, J., "Endpoints and Endpoint Names: A Proposed
Enhancement to the Internet Architecture", Enhancement to the Internet Architecture", 1999,
URL http://www.chiappa.net/~jnc/tech/endpoints.txt, 1999. <http://mercury.lcs.mit.edu/~jnc/tech/endpoints.txt>.
[heer-end-host] [heer-end-host]
Heer, T., Hummen, R., Komu, M., Goetz, S., and K. Wehre, Heer, T., Hummen, R., Komu, M., Gotz, S., and K. Wehrle,
"End-host Authentication and Authorization for Middleboxes "End-Host Authentication and Authorization for Middleboxes
based on a Cryptographic Namespace", ICC2009 Communication Based on a Cryptographic Namespace", 2009 IEEE
and Information Systems Security Symposium, , 2009. International Conference on Communications,
DOI 10.1109/ICC.2009.5198984, 2009,
<https://doi.org/10.1109/ICC.2009.5198984>.
[heer-midauth] [heer-midauth]
Heer, T. and M. Komu, "End-Host Authentication for HIP Heer, T., Ed., Hummen, R., Wehrle, K., and M. Komu, "End-
Middleboxes", Working draft draft-heer-hip-middle-auth-02, Host Authentication for HIP Middleboxes", Work in
September 2009. Progress, Internet-Draft, draft-heer-hip-middle-auth-04,
31 October 2011, <https://datatracker.ietf.org/doc/html/
draft-heer-hip-middle-auth-04>.
[henderson-vpls] [henderson-vpls]
Henderson, T. and D. Mattes, "HIP-based Virtual Private Henderson, T. R., Venema, S. C., and D. Mattes, "HIP-based
LAN Service (HIPLS)", Working draft draft-henderson-hip- Virtual Private LAN Service (HIPLS)", Work in Progress,
vpls-07, Dec 2013. Internet-Draft, draft-henderson-hip-vpls-11, 3 August
2016, <https://datatracker.ietf.org/doc/html/draft-
henderson-hip-vpls-11>.
[hip-dex] Moskowitz, R., Ed., Hummen, R., and M. Komu, "HIP Diet
EXchange (DEX)", Work in Progress, Internet-Draft, draft-
ietf-hip-dex-24, 19 January 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-hip-dex-
24>.
[hip-lte] Liyanage, M., Kumar, P., Ylianttila, M., and A. Gurtov, [hip-lte] Liyanage, M., Kumar, P., Ylianttila, M., and A. Gurtov,
"Novel secure VPN architectures for LTE backhaul "Novel secure VPN architectures for LTE backhaul
networks", Security and Communication Networks DOI networks", Security and Communication Networks, Vol. 9,
10.1002/sec.1411, November 2015. pp. 1198-1215, DOI 10.1002/sec.1411, January 2016,
<https://doi.org/10.1002/sec.1411>.
[hip-srtp] [hip-srtp] Tschofenig, H., Shanmugam, M., and F. Muenz, "Using SRTP
Tschofenig, H., Muenz, F., and M. Shanmugam, "Using SRTP transport format with HIP", Work in Progress, Internet-
transport format with HIP", Working draft draft- Draft, draft-tschofenig-hiprg-hip-srtp-02, 25 October
tschofenig-hiprg-hip-srtp-01, October 2005. 2006, <https://datatracker.ietf.org/doc/html/draft-
tschofenig-hiprg-hip-srtp-02>.
[hummen] Hummen, R., Hiller, J., Henze, M., and K. Wehrle, "Slimfit [hummen] Hummen, R., Hiller, J., Henze, M., and K. Wehrle, "Slimfit
- A HIP DEX Compression Layer for the IP-based Internet of - A HIP DEX compression layer for the IP-based Internet of
Things", Wireless and Mobile Computing, Networking and Things", 2013 IEEE 9th International Conference on
Communications (WiMob), 2013 IEEE 9th International Wireless and Mobile Computing, Networking and
Conference on , page 259-266. DOI: Communications (WiMob), pp. 259-266,
10.1109/WiMOB.2013.6673370, October 2013. DOI 10.1109/WiMOB.2013.6673370, October 2013,
<https://doi.org/10.1109/WiMOB.2013.6673370>.
[IEEE.802-15-4.2011] [IEEE.802.15.4]
"Information technology - Telecommunications and IEEE, "IEEE Standard for Low-Rate Wireless Networks",
information exchange between systems - Local and IEEE Standard 802.15.4, DOI 10.1109/IEEESTD.2020.9144691,
metropolitan area networks - Specific requirements - Part July 2020, <https://ieeexplore.ieee.org/document/9144691>.
15.4: Wireless Medium Access Control (MAC) and Physical
Layer (PHY) Specifications for Low-Rate Wireless Personal
Area Networks (WPANs)", IEEE Standard 802.15.4, September
2011, <http://standards.ieee.org/getieee802/
download/802.15.4-2011.pdf>.
[IEEE.802-15-9] [IEEE.802.15.9]
"IEEE Draft Recommended Practice for Transort of Key IEEE, "IEEE Draft Recommended Practice for Transport of
Management Protocol (KMP) Datagrams", IEEE P802.15.9/D04, Key Management Protocol (KMP) Datagrams",
May 2015. IEEE P802.15.9/D04, May 2015.
[karvonen-usable] [karvonen-usable]
Karvonen, K., Komu, M., and A. Gurtov, "Usable Security Karvonen, K., Komu, M., and A. Gurtov, "Usable security
Management with Host Identity Protocol", 7th ACS/IEEE management with host identity protocol", 2009 IEEE/ACS
International Conference on Computer Systems and International Conference on Computer Systems and
Applications, (AICCSA-2009), 2009. Applications, pp. 279-286,
DOI 10.1109/AICCSA.2009.5069337, 2009,
<https://doi.org/10.1109/AICCSA.2009.5069337>.
[komu-cloud] [komu-cloud]
Komu, M., Sethi, M., Mallavarapu, R., Oirola, H., Khan, Komu, M., Sethi, M., Mallavarapu, R., Oirola, H., Khan,
R., and S. Tarkoma, "Secure Networking for Virtual R., and S. Tarkoma, "Secure Networking for Virtual
Machines in the Cloud", International Workshop on Power Machines in the Cloud", 2012 IEEE International Conference
and QoS Aware Computing (PQoSCom2012), IEEE, ISBN: on Cluster Computing Workshops, pp. 88-96,
978-1-4244-8567-3, September 2012. DOI 10.1109/ClusterW.2012.29, 2012,
<https://doi.org/10.1109/ClusterW.2012.29>.
[komu-diss] [komu-diss]
Komu, M., "A Consolidated Namespace for Network Komu, M., "A Consolidated Namespace for Network
Applications, Developers, Administrators and Users", Applications, Developers, Administrators and Users",
Dissertation, Aalto University, Espoo, Finland ISBN: Dissertation, Aalto University, Espoo, Finland,
978-952-60-4904-5 (printed), ISBN: 978-952-60-4905-2 ISBN 978-952-60-4904-5 (printed), ISBN 978-952-60-4905-2
(electronic). , December 2012. (electronic), December 2012.
[komu-leap] [komu-leap]
Komu, M. and J. Lindqvist, "Leap-of-Faith Security is Komu, M. and J. Lindqvist, "Leap-of-Faith Security is
Enough for IP Mobility", 6th Annual IEEE Consumer Enough for IP Mobility", 2009 6th IEEE Consumer
Communications and Networking Conference IEEE CCNC 2009, Communications and Networking Conference, Las Vegas, NV,
Las Vegas, Nevada, , January 2009. USA, pp. 1-5, DOI 10.1109/CCNC.2009.4784729, January 2009,
<https://doi.org/10.1109/CCNC.2009.4784729>.
[komu-mitigation] [komu-mitigation]
Komu, M., Tarkoma, S., and A. Lukyanenko, "Mitigation of Komu, M., Tarkoma, S., and A. Lukyanenko, "Mitigation of
Unsolicited Traffic Across Domains with Host Identities Unsolicited Traffic Across Domains with Host Identities
and Puzzles", 15th Nordic Conference on Secure IT Systems and Puzzles", 15th Nordic Conference on Secure IT Systems,
(NordSec 2010), Springer Lecture Notes in Computer NordSec 2010, Lecture Notes in Computer Science, Vol.
Science, Volume 7127, pp. 33-48, ISBN: 978-3-642-27936-2, 7127, pp. 33-48, Springer, ISBN 978-3-642-27936-2,
October 2010. DOI 10.1007/978-3-642-27937-9_3, October 2010,
<https://doi.org/10.1007/978-3-642-27937-9_3>.
[kovacshazi-host] [kovacshazi-host]
Kovacshazi, Z. and R. Vida, "Host Identity Specific Kovacshazi, Z. and R. Vida, "Host Identity Specific
Multicast", International conference on Networking and Multicast", International Conference on Networking and
Services (ICNS'06), IEEE Computer Society, Los Alamitos, Services (ICNS '07), Athens, Greece, pp. 1-1,
CA, USA, http://doi.ieeecomputersociety.org/10.1109/ DOI 10.1109/ICNS.2007.66, 2007,
ICNS.2007.66, 2007. <https://doi.org/10.1109/ICNS.2007.66>.
[leva-barriers] [levae-barriers]
Levae, A., Komu, M., and S. Luukkainen, "Adoption Barriers Levä, T., Komu, M., and S. Luukkainen, "Adoption barriers
of Network-layer Protocols: the Case of Host Identity of network layer protocols: the case of host identity
Protocol", The International Journal of Computer and protocol", Computer Networks, Vol. 57, Issue 10, pp.
Telecommunications Networking, ISSN: 1389-1286, March 2218-2232, ISSN 1389-1286,
2013. DOI 10.1016/j.comnet.2012.11.024, March 2013,
<https://doi.org/10.1016/j.comnet.2012.11.024>.
[lindqvist-enterprise] [lindqvist-enterprise]
Lindqvist, J., Vehmersalo, E., Manner, J., and M. Komu, Lindqvist, J., Vehmersalo, E., Komu, M., and J. Manner,
"Enterprise Network Packet Filtering for Mobile "Enterprise Network Packet Filtering for Mobile
Cryptographic Identities", International Journal of Cryptographic Identities", International Journal of
Handheld Computing Research, 1 (1), 79-94, , January-March Handheld Computing Research (IJHCR), Vol. 1, Issue 1, pp.
2010. 79-94, DOI 10.4018/jhcr.2010090905, 2010,
<https://doi.org/10.4018/jhcr.2010090905>.
[Nik2001] Nikander, P., "Denial-of-Service, Address Ownership, and [Nik2001] Nikander, P., "Denial-of-Service, Address Ownership, and
Early Authentication in the IPv6 World", in Proceesings Early Authentication in the IPv6 World", 9th International
of Security Protocols, 9th International Workshop, Workshop on Security Protocols, Security Protocols 2001,
Cambridge, UK, April 25-27 2001, LNCS 2467, pp. 12-26, Lecture Notes in Computer Science, Vol. 2467, pp. 12-21,
Springer, 2002. Springer, DOI 10.1007/3-540-45807-7_3, 2002,
<https://doi.org/10.1007/3-540-45807-7_3>.
[nsrg-report] [nsrg-report]
Lear, E. and R. Droms, "What's In A Name:Thoughts from the Lear, E. and R. Droms, "What's In A Name: Thoughts from
NSRG", draft-irtf-nsrg-report-10 (work in progress), the NSRG", Work in Progress, Internet-Draft, draft-irtf-
September 2003. nsrg-report-10, 22 September 2003,
<https://datatracker.ietf.org/doc/html/draft-irtf-nsrg-
report-10>.
[paine-hip] [paine-hip]
Paine, R., "Beyond HIP: The End to Hacking As We Know It", Paine, R. H., "Beyond HIP: The End to Hacking As We Know
BookSurge Publishing, ISBN: 1439256047, 9781439256046, It", BookSurge Publishing, ISBN-10 1439256047,
2009. ISBN-13 978-1439256046, 2009.
[pham-leap] [pham-leap]
Pham, V. and T. Aura, "Security Analysis of Leap-of-Faith Pham, V. and T. Aura, "Security Analysis of Leap-of-Faith
Protocols", Seventh ICST International Conference on Protocols", 7th International ICST Conference, Security
Security and Privacy for Communication Networks, , and Privacy for Communication Networks, SecureComm 2011,
September 2011. Lecture Notes of the Institute for Computer Sciences,
Social Informatics and Telecommunications Engineering,
Vol. 96, DOI 10.1007/978-3-642-31909-9_19, 2012,
<https://doi.org/10.1007/978-3-642-31909-9_19>.
[ranjbar-synaptic] [ranjbar-synaptic]
Ranjbar, A., Komu, M., Salmela, P., and T. Aura, Ranjbar, A., Komu, M., Salmela, P., and T. Aura,
"SynAPTIC: Secure and Persistent Connectivity for "SynAPTIC: Secure and Persistent Connectivity for
Containers", 2017 17th IEEE/ACM International Symposium on Containers", 2017 17th IEEE/ACM International Symposium on
Cluster, Cloud and Grid Computing (CCGRID), Madrid, 2017, Cluster, Cloud and Grid Computing (CCGRID), Madrid, 2017,
pp. 262-267 doi: 10.1109/CCGRID.2017.62, 2017. pp. 262-267, DOI 10.1109/CCGRID.2017.62, 2017,
<https://doi.org/10.1109/CCGRID.2017.62>.
[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound, [RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)", "Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997, RFC 2136, DOI 10.17487/RFC2136, April 1997,
<https://www.rfc-editor.org/info/rfc2136>. <https://www.rfc-editor.org/info/rfc2136>.
[RFC2535] Eastlake 3rd, D., "Domain Name System Security
Extensions", RFC 2535, DOI 10.17487/RFC2535, March 1999,
<https://www.rfc-editor.org/info/rfc2535>.
[RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address [RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address
Translation - Protocol Translation (NAT-PT)", RFC 2766, Translation - Protocol Translation (NAT-PT)", RFC 2766,
DOI 10.17487/RFC2766, February 2000, <https://www.rfc- DOI 10.17487/RFC2766, February 2000,
editor.org/info/rfc2766>. <https://www.rfc-editor.org/info/rfc2766>.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022, Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001, <https://www.rfc- DOI 10.17487/RFC3022, January 2001,
editor.org/info/rfc3022>. <https://www.rfc-editor.org/info/rfc3022>.
[RFC3102] Borella, M., Lo, J., Grabelsky, D., and G. Montenegro, [RFC3102] Borella, M., Lo, J., Grabelsky, D., and G. Montenegro,
"Realm Specific IP: Framework", RFC 3102, "Realm Specific IP: Framework", RFC 3102,
DOI 10.17487/RFC3102, October 2001, <https://www.rfc- DOI 10.17487/RFC3102, October 2001,
editor.org/info/rfc3102>. <https://www.rfc-editor.org/info/rfc3102>.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, Ed., "Extensible Authentication Protocol Levkowetz, Ed., "Extensible Authentication Protocol
(EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
<https://www.rfc-editor.org/info/rfc3748>. <https://www.rfc-editor.org/info/rfc3748>.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, DOI 10.17487/RFC3972, March 2005, RFC 3972, DOI 10.17487/RFC3972, March 2005,
<https://www.rfc-editor.org/info/rfc3972>. <https://www.rfc-editor.org/info/rfc3972>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005,
<https://www.rfc-editor.org/info/rfc4033>.
[RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E. [RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.
Nordmark, "Mobile IP Version 6 Route Optimization Security Nordmark, "Mobile IP Version 6 Route Optimization Security
Design Background", RFC 4225, DOI 10.17487/RFC4225, Design Background", RFC 4225, DOI 10.17487/RFC4225,
December 2005, <https://www.rfc-editor.org/info/rfc4225>. December 2005, <https://www.rfc-editor.org/info/rfc4225>.
[RFC4306] Kaufman, C., Ed., "Internet Key Exchange (IKEv2)
Protocol", RFC 4306, DOI 10.17487/RFC4306, December 2005,
<https://www.rfc-editor.org/info/rfc4306>.
[RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through
Network Address Translations (NATs)", RFC 4380, Network Address Translations (NATs)", RFC 4380,
DOI 10.17487/RFC4380, February 2006, <https://www.rfc- DOI 10.17487/RFC4380, February 2006,
editor.org/info/rfc4380>. <https://www.rfc-editor.org/info/rfc4380>.
[RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol
(HIP) Architecture", RFC 4423, DOI 10.17487/RFC4423, May (HIP) Architecture", RFC 4423, DOI 10.17487/RFC4423, May
2006, <https://www.rfc-editor.org/info/rfc4423>. 2006, <https://www.rfc-editor.org/info/rfc4423>.
[RFC5218] Thaler, D. and B. Aboba, "What Makes for a Successful [RFC5218] Thaler, D. and B. Aboba, "What Makes for a Successful
Protocol?", RFC 5218, DOI 10.17487/RFC5218, July 2008, Protocol?", RFC 5218, DOI 10.17487/RFC5218, July 2008,
<https://www.rfc-editor.org/info/rfc5218>. <https://www.rfc-editor.org/info/rfc5218>.
[RFC5338] Henderson, T., Nikander, P., and M. Komu, "Using the Host [RFC5338] Henderson, T., Nikander, P., and M. Komu, "Using the Host
Identity Protocol with Legacy Applications", RFC 5338, Identity Protocol with Legacy Applications", RFC 5338,
DOI 10.17487/RFC5338, September 2008, <https://www.rfc- DOI 10.17487/RFC5338, September 2008,
editor.org/info/rfc5338>. <https://www.rfc-editor.org/info/rfc5338>.
[RFC5887] Carpenter, B., Atkinson, R., and H. Flinck, "Renumbering [RFC5887] Carpenter, B., Atkinson, R., and H. Flinck, "Renumbering
Still Needs Work", RFC 5887, DOI 10.17487/RFC5887, May Still Needs Work", RFC 5887, DOI 10.17487/RFC5887, May
2010, <https://www.rfc-editor.org/info/rfc5887>. 2010, <https://www.rfc-editor.org/info/rfc5887>.
[RFC6078] Camarillo, G. and J. Melen, "Host Identity Protocol (HIP) [RFC6078] Camarillo, G. and J. Melen, "Host Identity Protocol (HIP)
Immediate Carriage and Conveyance of Upper-Layer Protocol Immediate Carriage and Conveyance of Upper-Layer Protocol
Signaling (HICCUPS)", RFC 6078, DOI 10.17487/RFC6078, Signaling (HICCUPS)", RFC 6078, DOI 10.17487/RFC6078,
January 2011, <https://www.rfc-editor.org/info/rfc6078>. January 2011, <https://www.rfc-editor.org/info/rfc6078>.
[RFC6250] Thaler, D., "Evolution of the IP Model", RFC 6250, [RFC6250] Thaler, D., "Evolution of the IP Model", RFC 6250,
DOI 10.17487/RFC6250, May 2011, <https://www.rfc- DOI 10.17487/RFC6250, May 2011,
editor.org/info/rfc6250>. <https://www.rfc-editor.org/info/rfc6250>.
[RFC6281] Cheshire, S., Zhu, Z., Wakikawa, R., and L. Zhang, [RFC6281] Cheshire, S., Zhu, Z., Wakikawa, R., and L. Zhang,
"Understanding Apple's Back to My Mac (BTMM) Service", "Understanding Apple's Back to My Mac (BTMM) Service",
RFC 6281, DOI 10.17487/RFC6281, June 2011, RFC 6281, DOI 10.17487/RFC6281, June 2011,
<https://www.rfc-editor.org/info/rfc6281>. <https://www.rfc-editor.org/info/rfc6281>.
[RFC6317] Komu, M. and T. Henderson, "Basic Socket Interface [RFC6317] Komu, M. and T. Henderson, "Basic Socket Interface
Extensions for the Host Identity Protocol (HIP)", Extensions for the Host Identity Protocol (HIP)",
RFC 6317, DOI 10.17487/RFC6317, July 2011, RFC 6317, DOI 10.17487/RFC6317, July 2011,
<https://www.rfc-editor.org/info/rfc6317>. <https://www.rfc-editor.org/info/rfc6317>.
[RFC6537] Ahrenholz, J., "Host Identity Protocol Distributed Hash [RFC6537] Ahrenholz, J., "Host Identity Protocol Distributed Hash
Table Interface", RFC 6537, DOI 10.17487/RFC6537, February Table Interface", RFC 6537, DOI 10.17487/RFC6537, February
2012, <https://www.rfc-editor.org/info/rfc6537>. 2012, <https://www.rfc-editor.org/info/rfc6537>.
[RFC6538] Henderson, T. and A. Gurtov, "The Host Identity Protocol [RFC6538] Henderson, T. and A. Gurtov, "The Host Identity Protocol
(HIP) Experiment Report", RFC 6538, DOI 10.17487/RFC6538, (HIP) Experiment Report", RFC 6538, DOI 10.17487/RFC6538,
March 2012, <https://www.rfc-editor.org/info/rfc6538>. March 2012, <https://www.rfc-editor.org/info/rfc6538>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection [RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435, Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, <https://www.rfc-editor.org/info/rfc7435>. December 2014, <https://www.rfc-editor.org/info/rfc7435>.
[sarela-bloom] [sarela-bloom]
Saerelae, M., Esteve Rothenberg, C., Zahemszky, A., Särelä, M., Esteve Rothenberg, C., Zahemszky, A.,
Nikander, P., and J. Ott, "BloomCasting: Security in Bloom Nikander, P., and J. Ott, "BloomCasting: Security in Bloom
filter based multicast", , Lecture Notes in Computer Filter Based Multicast", Information Security Technology
Science 2012, , pages 1-16, Springer Berlin Heidelberg, for Applications, NordSec 2010, Lecture Notes in Computer
2012. Science, Vol. 7127, pages 1-16, Springer,
DOI 10.1007/978-3-642-27937-9_1, 2012,
<https://doi.org/10.1007/978-3-642-27937-9_1>.
[schuetz-intermittent] [schuetz-intermittent]
Schuetz, S., Eggert, L., Schmid, S., and M. Brunner, Schütz, S., Eggert, L., Schmid, S., and M. Brunner,
"Protocol enhancements for intermittently connected "Protocol enhancements for intermittently connected
hosts", SIGCOMM Comput. Commun. Rev., 35(3):5-18, , July hosts", ACM SIGCOMM Computer Communication Review, Vol.
2005. 35, Issue 3, pp. 5-18, DOI 10.1145/1070873.1070875, July
2005, <https://doi.org/10.1145/1070873.1070875>.
[shields-hip] [shields-hip]
Shields, C. and J. Garcia-Luna-Aceves, "The HIP protocol Shields, C. and J. J. Garcia-Luna-Aceves, "The HIP
for hierarchical multicast routing", Proceedings of the protocol for hierarchical multicast routing", Proceedings
seventeenth annual ACM symposium on Principles of of the seventeenth annual ACM symposium on Principles of
distributed computing, pages 257-266. ACM, New York, NY, distributed computing, pp. 257-266, ISBN 0-89791-977-7,
USA, ISBN: 0-89791-977-7, DOI: 10.1145/277697.277744, DOI 10.1145/277697.277744, 1998,
1998. <https://doi.org/10.1145/277697.277744>.
[tempered-networks] [tempered-networks]
"Identity-Defined Network (IDN) Architecture: Unified, Tempered Networks, "Identity-Defined Network (IDN)
Secure Networking Made Simple", White Paper , 2016. Architecture: Unified, Secure Networking Made Simple",
White Paper, 2016.
[tritilanunt-dos] [tritilanunt-dos]
Tritilanunt, S., Boyd, C., Foo, E., and J. Nieto, Tritilanunt, S., Boyd, C., Foo, E., and J.M.G. Nieto,
"Examining the DoS Resistance of HIP", OTM Workshops (1), "Examining the DoS Resistance of HIP", On the Move to
volume 4277 of Lecture Notes in Computer Science, pages Meaningful Internet Systems 2006: OTM 2006 Workshops,
616-625,Springer , 2006. Lecture Notes in Computer Science, Vol. 4277, pp. 616-625,
Springer, DOI 10.1007/11915034_85, 2006,
<https://doi.org/10.1007/11915034_85>.
[urien-rfid] [urien-rfid]
Urien, P., Chabanne, H., Bouet, M., de Cunha, D., Guyot, Urien, P., Chabanne, H., Pepin, C., Orga, S., Bouet, M.,
V., Pujolle, G., Paradinas, P., Gressier, E., and J. de Cunha, D.O., Guyot, V., Pujolle, G., Paradinas, P.,
Susini, "HIP-based RFID Networking Architecture", IFIP Gressier, E., and J.-F. Susini, "HIP-based RFID Networking
International Conference on Wireless and Optical Architecture", 2007 IFIP International Conference on
Communications Networks, DOI: 10.1109/WOCN.2007.4284140, Wireless and Optical Communications Networks, pp. 1-5,
July 2007. DOI 10.1109/WOCN.2007.4284140, 2007,
<https://doi.org/10.1109/WOCN.2007.4284140>.
[urien-rfid-draft] [urien-rfid-draft]
Urien, P., Lee, G., and G. Pujolle, "HIP support for Urien, P., Lee, G. M., and G. Pujolle, "HIP support for
RFIDs", IRTF Working draft draft-irtf-hiprg-rfid-07, April RFIDs", Work in Progress, Internet-Draft, draft-irtf-
2013. hiprg-rfid-07, 23 April 2013,
<https://datatracker.ietf.org/doc/html/draft-irtf-hiprg-
rfid-07>.
[varjonen-split] [varjonen-split]
Varjonen, S., Komu, M., and A. Gurtov, "Secure and Varjonen, S., Komu, M., and A. Gurtov, "Secure and
Efficient IPv4/IPv6 Handovers Using Host-Based Identifier- Efficient IPv4/IPv6 Handovers Using Host-Based Identifier-
Location Split", Journal of Communications Software and Location Split", Journal of Communications Software and
Systems, 6(1), 2010, ISSN: 18456421, 2010. Systems, Vol. 6, Issue 1, ISSN 18456421,
DOI 10.24138/jcomss.v6i1.193, 2010,
<https://doi.org/10.24138/jcomss.v6i1.193>.
[xin-hip-lib] [xin-hip-lib]
Xin, G., "Host Identity Protocol Version 2.5", Master's Xin, G., "Host Identity Protocol Version 2.5", Master's
Thesis, Aalto University, Espoo, Finland, , June 2012. Thesis, Aalto University, Espoo, Finland, June 2012.
[xueyong-hip]
Xueyong, Z., Zhiguo, D., and W. Xinling, "A Multicast
Routing Algorithm Applied to HIP-Multicast Model",
Proceedings of the 2011 International Conference on
Network Computing and Information Security - Volume 01
(NCIS '11), Vol. 1. IEEE Computer Society, Washington, DC,
USA, pages 169-174, DOI: 10.1109/NCIS.2011.42, 2011.
[xueyong-secure]
Xueyong, Z. and J. Atwood, "A Secure Multicast Model for
Peer-to-Peer and Access Networks Using the Host Identity
Protocol", Consumer Communications and Networking
Conference. CCNC 2007. 4th IEEE, pages 1098,1102, DOI:
10.1109/CCNC.2007.221, January 2007.
[ylitalo-diss] [ylitalo-diss]
Ylitalo, J., "Secure Mobility at Multiple Granularity Ylitalo, J., "Secure Mobility at Multiple Granularity
Levels over Heterogeneous Datacom Networks", Dissertation, Levels over Heterogeneous Datacom Networks", Dissertation,
Helsinki University of Technology, Espoo, Finland ISBN Helsinki University of Technology, Espoo, Finland,
978-951-22-9531-9, 2008. ISBN 978-951-22-9531-9, 2008.
[ylitalo-spinat] [ylitalo-spinat]
Ylitalo, J., Salmela, P., and H. Tschofenig, "SPINAT: Ylitalo, J., Salmela, P., and H. Tschofenig, "SPINAT:
Integrating IPsec into overlay routing", Proceedings of Integrating IPsec into Overlay Routing", First
the First International Conference on Security and Privacy International Conference on Security and Privacy for
for Emerging Areas in Communication Networks (SecureComm Emerging Areas in Communication Networks, SECURECOMM'05,
2005). Athens, Greece. IEEE Computer Society, pages Athens, Greece, pp. 315-326, ISBN 0-7695-2369-2,
315-326, ISBN: 0-7695-2369-2, September 2005. DOI 10.1109/SECURECOMM.2005.53, 2005,
<https://doi.org/10.1109/SECURECOMM.2005.53>.
[zhang-revocation] [zhang-revocation]
Zhang, D., Kuptsov, D., and S. Shen, "Host Identifier Zhang, D., Kuptsov, D., and S. Shen, "Host Identifier
Revocation in HIP", IRTF Working draft draft-irtf-hiprg- Revocation in HIP", Work in Progress, Internet-Draft,
revocation-05, Mar 2012. draft-irtf-hiprg-revocation-05, 9 March 2012,
<https://datatracker.ietf.org/doc/html/draft-irtf-hiprg-
revocation-05>.
Appendix A. Design considerations [zhu-hip] Zhu, X., Ding, Z., and X. Wang, "A Multicast Routing
Algorithm Applied to HIP-Multicast Model", 2011
International Conference on Network Computing and
Information Security, Guilin, China, pp. 169-174,
DOI 10.1109/NCIS.2011.42, 2011,
<https://doi.org/10.1109/NCIS.2011.42>.
[zhu-secure]
Zhu, X. and J. W. Atwood, "A Secure Multicast Model for
Peer-to-Peer and Access Networks Using the Host Identity
Protocol", 2007 4th IEEE Consumer Communications and
Networking Conference, Las Vegas, NV, USA, pages
1098-1102, DOI 10.1109/CCNC.2007.221, 2007,
<https://doi.org/10.1109/CCNC.2007.221>.
Appendix A. Design Considerations
A.1. Benefits of HIP A.1. Benefits of HIP
In the beginning, the network layer protocol (i.e., IP) had the In the beginning, the network layer protocol (i.e., IP) had the
following four "classic" invariants: following four "classic" invariants:
1. Non-mutable: The address sent is the address received. 1. Non-mutable: The address sent is the address received.
2. Non-mobile: The address doesn't change during the course of an 2. Non-mobile: The address doesn't change during the course of an
"association". "association".
skipping to change at page 39, line 6 skipping to change at line 1810
source and destination addresses. source and destination addresses.
4. Omniscient: Each host knows what address a partner host can use 4. Omniscient: Each host knows what address a partner host can use
to send packets to it. to send packets to it.
Actually, the fourth can be inferred from 1 and 3, but it is worth Actually, the fourth can be inferred from 1 and 3, but it is worth
mentioning explicitly for reasons that will be obvious soon if not mentioning explicitly for reasons that will be obvious soon if not
already. already.
In the current "post-classic" world, we are intentionally trying to In the current "post-classic" world, we are intentionally trying to
get rid of the second invariant (both for mobility and for multi- get rid of the second invariant (both for mobility and for
homing), and we have been forced to give up the first and the fourth. multihoming), and we have been forced to give up the first and the
Realm Specific IP [RFC3102] is an attempt to reinstate the fourth fourth. Realm Specific IP [RFC3102] is an attempt to reinstate the
invariant without the first invariant. IPv6 is attempts to reinstate fourth invariant without the first invariant. IPv6 attempts to
the first invariant. reinstate the first invariant.
Few client-side systems on the Internet have DNS names that are Few client-side systems on the Internet have DNS names that are
meaningful. That is, if they have a Fully Qualified Domain Name meaningful. That is, if they have a Fully Qualified Domain Name
(FQDN), that name typically belongs to a NAT device or a dial-up (FQDN), that name typically belongs to a NAT device or a dial-up
server, and does not really identify the system itself but its server, and does not really identify the system itself but its
current connectivity. FQDNs (and their extensions as email names) current connectivity. FQDNs (and their extensions as email names)
are application-layer names; more frequently naming services than are application-layer names; more frequently naming services than
particular systems. This is why many systems on the Internet are not particular systems. This is why many systems on the Internet are not
registered in the DNS; they do not have services of interest to other registered in the DNS; they do not have services of interest to other
Internet hosts. Internet hosts.
DNS names are references to IP addresses. This only demonstrates the DNS names are references to IP addresses. This only demonstrates the
interrelationship of the networking and application layers. DNS, as interrelationship of the networking and application layers. DNS, as
the Internet's only deployed and distributed database, is also the the Internet's only deployed and distributed database, is also the
repository of other namespaces, due in part to DNSSEC and application repository of other namespaces, due in part to DNSSEC and
specific key records. Although each namespace can be stretched (IP application-specific key records. Although each namespace can be
with v6, DNS with KEY records), neither can adequately provide for stretched (IP with v6, DNS with KEY records), neither can adequately
host authentication or act as a separation between internetworking provide for host authentication or act as a separation between
and transport layers. internetworking and transport layers.
The Host Identity (HI) namespace fills an important gap between the The Host Identity (HI) namespace fills an important gap between the
IP and DNS namespaces. An interesting thing about the HI is that it IP and DNS namespaces. An interesting thing about the HI is that it
actually allows a host to give up all but the 3rd network-layer actually allows a host to give up all but the 3rd network-layer
invariant. That is to say, as long as the source and destination invariant. That is to say, as long as the source and destination
addresses in the network-layer protocol are reversible, HIP takes addresses in the network-layer protocol are reversible, HIP takes
care of host identification, and reversibility allows a local host to care of host identification, and reversibility allows a local host to
receive a packet back from a remote host. The address changes receive a packet back from a remote host. The address changes
occurring during NAT transit (non-mutable) or host movement (non- occurring during NAT transit (non-mutable) or host movement (non-
omniscient or non-mobile) can be managed by the HIP layer. omniscient or non-mobile) can be managed by the HIP layer.
With the exception of High-Performance Computing applications, the With the exception of high-performance computing applications, the
Sockets API is the most common way to develop network applications. sockets API is the most common way to develop network applications.
Applications use the Sockets API either directly or indirectly Applications use the sockets API either directly or indirectly
through some libraries or frameworks. However, the Sockets API is through some libraries or frameworks. However, the sockets API is
based on the assumption of static IP addresses, and DNS with its based on the assumption of static IP addresses, and DNS with its
lifetime values was invented at later stages during the evolution of lifetime values was invented at later stages during the evolution of
the Internet. Hence, the Sockets API does not deal with the lifetime the Internet. Hence, the sockets API does not deal with the lifetime
of addresses [RFC6250]. As the majority of the end-user equipment is of addresses [RFC6250]. As the majority of the end-user equipment is
mobile today, their addresses are effectively ephemeral, but the mobile today, their addresses are effectively ephemeral, but the
Sockets API still gives a fallacious illusion of persistent IP sockets API still gives a fallacious illusion of persistent IP
addresses to the unwary developer. HIP can be used to solidify this addresses to the unwary developer. HIP can be used to solidify this
illusion because HIP provides persistent surrogate addresses to the illusion because HIP provides persistent, surrogate addresses to the
application layer in the form of LSIs and HITs. application layer in the form of LSIs and HITs.
The persistent identifiers as provided by HIP are useful in multiple The persistent identifiers as provided by HIP are useful in multiple
scenarios (see, e.g., [ylitalo-diss] or [komu-diss], for a more scenarios (see, e.g., [ylitalo-diss] or [komu-diss] for a more
elaborate discussion): elaborate discussion):
o When a mobile host moves physically between two different WLAN * When a mobile host moves physically between two different WLAN
networks and obtains a new address, an application using the networks and obtains a new address, an application using the
identifiers remains isolated regardless of the topology changes identifiers remains isolated regardless of the topology changes
while the underlying HIP layer re-establishes connectivity (i.e. a while the underlying HIP layer reestablishes connectivity (i.e., a
horizontal handoff). horizontal handoff).
o Similarly, the application utilizing the identifiers remains again * Similarly, the application utilizing the identifiers remains again
unaware of the topological changes when the underlying host unaware of the topological changes when the underlying host
equipped with WLAN and cellular network interfaces switches equipped with WLAN and cellular network interfaces switches
between the two different access technologies (i.e. a vertical between the two different access technologies (i.e., a vertical
handoff). handoff).
o Even when hosts are located in private address realms, * Even when hosts are located in private address realms,
applications can uniquely distinguish different hosts from each applications can uniquely distinguish different hosts from each
other based on their identifiers. In other words, it can be other based on their identifiers. In other words, it can be
stated that HIP improves Internet transparency for the application stated that HIP improves Internet transparency for the application
layer [komu-diss]. layer [komu-diss].
o Site renumbering events for services can occur due to corporate * Site renumbering events for services can occur due to corporate
mergers or acquisitions, or by changes in Internet Service mergers or acquisitions, or by changes in Internet service
Provider. They can involve changing the entire network prefix of provider. They can involve changing the entire network prefix of
an organization, which is problematic due to hard-coded addresses an organization, which is problematic due to hard-coded addresses
in service configuration files or cached IP addresses at the in service configuration files or cached IP addresses at the
client side [RFC5887]. Considering such human errors, a site client side [RFC5887]. Considering such human errors, a site
employing location-independent identifiers as promoted by HIP may employing location-independent identifiers as promoted by HIP may
experience fewer problems while renumbering their network. experience fewer problems while renumbering their network.
o More agile IPv6 interoperability can be achieved, as discussed in * More agile IPv6 interoperability can be achieved, as discussed in
Section 4.4. IPv6-based applications can communicate using HITs Section 4.4. IPv6-based applications can communicate using HITs
with IPv4-based applications that are using LSIs. Additionally, with IPv4-based applications that are using LSIs. Additionally,
the underlying network type (IPv4 or IPv6) becomes independent of the underlying network type (IPv4 or IPv6) becomes independent of
the addressing family of the application. the addressing family of the application.
o HITs (or LSIs) can be used in IP-based access control lists as a * HITs (or LSIs) can be used in IP-based access control lists as a
more secure replacement for IPv6 addresses. Besides security, HIT more secure replacement for IPv6 addresses. Besides security,
based access control has two other benefits. First, the use of HIT-based access control has two other benefits. First, the use
HITs can potentially halve the size of access control lists of HITs can potentially halve the size of access control lists
because separate rules for IPv4 are not needed [komu-diss]. because separate rules for IPv4 are not needed [komu-diss].
Second, HIT-based configuration rules in HIP-aware middleboxes Second, HIT-based configuration rules in HIP-aware middleboxes
remain static and independent of topology changes, thus remain static and independent of topology changes, thus
simplifying administrative efforts particularly for mobile simplifying administrative efforts particularly for mobile
environments. For instance, the benefits of HIT-based access environments. For instance, the benefits of HIT-based access
control have been harnessed in the case of HIP-aware firewalls, control have been harnessed in the case of HIP-aware firewalls,
but can be utilized directly at the end-hosts as well [RFC6538]. but can be utilized directly at the end-hosts as well [RFC6538].
While some of these benefits could be and have been redundantly While some of these benefits could be and have been redundantly
implemented by individual applications, providing such generic implemented by individual applications, providing such generic
functionality at the lower layers is useful because it reduces functionality at the lower layers is useful because it reduces
software development effort and networking software bugs (as the software development effort and networking software bugs (as the
layer is tested with multiple applications). It also allows the layer is tested with multiple applications). It also allows the
developer to focus on building the application itself rather than developer to focus on building the application itself rather than
delving into the intricacies of mobile networking, thus facilitating delving into the intricacies of mobile networking, thus facilitating
separation of concerns. separation of concerns.
HIP could also be realized by combining a number of different HIP could also be realized by combining a number of different
protocols, but the complexity of the resulting software may become protocols, but the complexity of the resulting software may become
substantially larger, and the interaction between multiple possibly substantially larger, and the interaction between multiple, possibly
layered protocols may have adverse effects on latency and throughput. layered protocols may have adverse effects on latency and throughput.
It is also worth noting that virtually nothing prevents realizing the It is also worth noting that virtually nothing prevents realizing the
HIP architecture, for instance, as an application-layer library, HIP architecture, for instance, as an application-layer library,
which has been actually implemented in the past [xin-hip-lib]. which has been actually implemented in the past [xin-hip-lib].
However, the tradeoff in moving the HIP layer to the application However, the trade-off in moving the HIP layer to the application
layer is that legacy applications may not be supported. layer is that legacy applications may not be supported.
A.2. Drawbacks of HIP A.2. Drawbacks of HIP
In computer science, many problems can be solved with an extra layer In computer science, many problems can be solved with an extra layer
of indirection. However, the indirection always involves some costs of indirection. However, the indirection always involves some costs
as there is no such a thing as "free lunch". In the case of HIP, the as there is no such a thing as a "free lunch". In the case of HIP,
main costs could be stated as follows: the main costs could be stated as follows:
o In general, an additional layer and a namespace always involve * In general, an additional layer and a namespace always involve
some initial effort in terms of implementation, deployment and some initial effort in terms of implementation, deployment, and
maintenance. Some education of developers and administrators may maintenance. Some education of developers and administrators may
also be needed. However, the HIP community at the IETF has spent also be needed. However, the HIP community at the IETF has spent
years in experimenting, exploring, testing, documenting and years in experimenting, exploring, testing, documenting, and
implementing HIP to ease the adoption costs. implementing HIP to ease the adoption costs.
o HIP introduces a need to manage HIs and requires a centralized * HIP introduces a need to manage HIs and requires a centralized
approach to manage HIP-aware endpoints at scale. What were approach to manage HIP-aware endpoints at scale. What were
formerly IP address-based ACLs are now trusted HITs, and the HIT formerly IP address-based ACLs are now trusted HITs, and the HIT-
to IP address mappings as well as access policies must be managed. to-IP address mappings as well as access policies must be managed.
HIP-aware endpoints must also be able to operate autonomously to HIP-aware endpoints must also be able to operate autonomously to
ensure mobility and availability (an endpoint must be able to run ensure mobility and availability (an endpoint must be able to run
without having to have a persistent management connection). The without having to have a persistent management connection). The
users who want this better security and mobility of HIs instead of users who want this better security and mobility of HIs instead of
IP address based ACLs have to then manage this additional IP address-based ACLs have to then manage this additional
'identity layer' in a non-persistent fashion. As exemplified in 'identity layer' in a nonpersistent fashion. As exemplified in
Appendix A.3.5, these challenges have been already solved in an Appendix A.3.5, these challenges have been already solved in an
infrastructure setting to distribute policy and manage the infrastructure setting to distribute policy and manage the
mappings and trust relationships between HIP-aware endpoints. mappings and trust relationships between HIP-aware endpoints.
o HIP decouples identifier and locator roles of IP addresses. * HIP decouples identifier and locator roles of IP addresses.
Consequently, a mapping mechanism is needed to associate them Consequently, a mapping mechanism is needed to associate them
together. A failure to map a HIT to its corresponding locator may together. A failure to map a HIT to its corresponding locator may
result in failed connectivity because a HIT is "flat" by its result in failed connectivity because a HIT is "flat" by its
nature and cannot be looked up from the hierarchically organized nature and cannot be looked up from the hierarchically organized
DNS. HITs are flat by design due to a security tradeoff. The DNS. HITs are flat by design due to a security trade-off. The
more bits are allocated for the hash in the HIT, the less likely more bits that are allocated for the hash in the HIT, the less
there will be (malicious) collisions. likely there will be (malicious) collisions.
o From performance viewpoint, HIP control and data plane processing * From performance viewpoint, HIP control and data plane processing
introduces some overhead in terms of throughput and latency as introduces some overhead in terms of throughput and latency as
elaborated below. elaborated below.
Related to deployment drawbacks, firewalls are commonly used to Related to deployment drawbacks, firewalls are commonly used to
control access to various services and devices in the current control access to various services and devices in the current
Internet. Since HIP introduces an additional namespace, it is Internet. Since HIP introduces an additional namespace, it is
expected that also the HIP namespace would be filtered for unwanted expected that the HIP namespace would be filtered for unwanted
connectivity. While this can be achieved with existing tools connectivity also. While this can be achieved with existing tools
directly in the end-hosts, filtering at the middleboxes requires directly in the end-hosts, filtering at the middleboxes requires
modifications to existing firewall software or additional middleboxes modifications to existing firewall software or additional middleboxes
[RFC6538]. [RFC6538].
The key exchange introduces some extra latency (two round trips) in The key exchange introduces some extra latency (two round trips) in
the initial transport-layer connection establishment between two the initial transport-layer connection establishment between two
hosts. With TCP, additional delay occurs if the underlying network hosts. With TCP, additional delay occurs if the underlying network
stack implementation drops the triggering SYN packet during the key stack implementation drops the triggering SYN packet during the key
exchange. The same cost may also occur during HIP handoff exchange. The same cost may also occur during HIP handoff
procedures. However, subsequent TCP sessions using the same HIP procedures. However, subsequent TCP sessions using the same HIP
association will not bear this cost (within the key lifetime). Both association will not bear this cost (within the key lifetime). Both
the key exchange and handoff penalties can be minimized by caching the key exchange and handoff penalties can be minimized by caching
TCP packets. The latter case can further be optimized with TCP user TCP packets. The latter case can further be optimized with TCP user
timeout extensions [RFC5482] as described in further detail by timeout extensions [RFC5482] as described in further detail by Schütz
Schuetz et al [schuetz-intermittent]. et al. [schuetz-intermittent].
The most CPU-intensive operations involve the use of the asymmetric The most CPU-intensive operations involve the use of the asymmetric
keys and Diffie-Hellman key derivation at the control plane, but this keys and Diffie-Hellman key derivation at the control plane, but this
occurs only during the key exchange, its maintenance (handoffs, occurs only during the key exchange, its maintenance (handoffs and
refreshing of key material) and tear-down procedures of HIP refreshing of key material), and teardown procedures of HIP
associations. The data plane is typically implemented with ESP associations. The data plane is typically implemented with ESP
because it has a smaller overhead due to symmetric key encryption. because it has a smaller overhead due to symmetric key encryption.
Naturally, even ESP involves some overhead in terms of latency Naturally, even ESP involves some overhead in terms of latency
(processing costs) and throughput (tunneling) (see, e.g., (processing costs) and throughput (tunneling) (see, e.g.,
[ylitalo-diss] for a performance evaluation). [ylitalo-diss] for a performance evaluation).
A.3. Deployment and adoption considerations A.3. Deployment and Adoption Considerations
This section describes some deployment and adoption considerations This section describes some deployment and adoption considerations
related to HIP from a technical perspective. related to HIP from a technical perspective.
A.3.1. Deployment analysis A.3.1. Deployment Analysis
HIP has been adapted and deployed in an industrial control network in HIP has been adapted and deployed in an industrial control network in
a production factory, in which HIP's strong network layer identity a production factory, in which HIP's strong network-layer identity
supports the secure coexistence of the control network with many supports the secure coexistence of the control network with many
untrusted network devices operated by third-party vendors untrusted network devices operated by third-party vendors
[paine-hip]. Similarly, HIP has also been included in a security [paine-hip]. Similarly, HIP has also been included in a security
product to support layer-two Virtual Private Networks product to support Layer 2 VPNs [henderson-vpls] to enable security
[henderson-vpls] to enable security zones in a supervisory control zones in a supervisory control and data acquisition (SCADA) network.
and data acquisition (SCADA) network. However, HIP has not been a However, HIP has not been a "wild success" [RFC5218] in the Internet
"wild success" [RFC5218] in the Internet as argued by Levae et al as argued by Levä et al. [levae-barriers]. Here, we briefly
[leva-barriers]. Here, we briefly highlight some of their findings highlight some of their findings based on interviews with 19 experts
based on interviews with 19 experts from the industry and academia. from the industry and academia.
From a marketing perspective, the demand for HIP has been low and From a marketing perspective, the demand for HIP has been low and
substitute technologies have been favored. Another identified reason substitute technologies have been favored. Another identified reason
has been that some technical misconceptions related to the early has been that some technical misconceptions related to the early
stages of HIP specifications still persist. Two identified stages of HIP specifications still persist. Two identified
misconceptions are that HIP does not support NAT traversal, and that misconceptions are that HIP does not support NAT traversal and that
HIP must be implemented in the OS kernel. Both of these claims are HIP must be implemented in the OS kernel. Both of these claims are
untrue; HIP does have NAT traversal extensions untrue; HIP does have NAT traversal extensions [RFC9028], and kernel
[I-D.ietf-hip-native-nat-traversal], and kernel modifications can be modifications can be avoided with modern operating systems by
avoided with modern operating systems by diverting packets for diverting packets for userspace processing.
userspace processing.
The analysis by Levae et al clarifies infrastructural requirements The analysis by Levä et al. clarifies infrastructural requirements
for HIP. In a minimal set up, a client and server machine have to for HIP. In a minimal setup, a client and server machine have to run
run HIP software. However, to avoid manual configurations, usually HIP software. However, to avoid manual configurations, usually DNS
DNS records for HIP are set up. For instance, the popular DNS server records for HIP are set up. For instance, the popular DNS server
software Bind9 does not require any changes to accommodate DNS software Bind9 does not require any changes to accommodate DNS
records for HIP because they can be supported in binary format in its records for HIP because they can be supported in binary format in its
configuration files [RFC6538]. HIP rendezvous servers and firewalls configuration files [RFC6538]. HIP rendezvous servers and firewalls
are optional. No changes are required to network address points, are optional. No changes are required to network address points,
NATs, edge routers or core networks. HIP may require holes in legacy NATs, edge routers, or core networks. HIP may require holes in
firewalls. legacy firewalls.
The analysis also clarifies the requirements for the host components The analysis also clarifies the requirements for the host components
that consist of three parts. First, a HIP control plane component is that consist of three parts. First, a HIP control plane component is
required, typically implemented as a userspace daemon. Second, a required, typically implemented as a userspace daemon. Second, a
data plane component is needed. Most HIP implementations utilize the data plane component is needed. Most HIP implementations utilize the
so called BEET mode of ESP that has been available since Linux kernel so-called Bound End-to-End Tunnel (BEET) mode of ESP that has been
2.6.27, but the BEET mode is also included as a userspace component available since Linux kernel 2.6.27, but the BEET mode is also
in a few of the implementations. Third, HIP systems usually provide included as a userspace component in a few of the implementations.
a DNS proxy for the local host that translates HIP DNS records to Third, HIP systems usually provide a DNS proxy for the local host
LSIs and HITs, and communicates the corresponding locators to HIP that translates HIP DNS records to LSIs and HITs, and communicates
userspace daemon. While the third component is not mandatory, it is the corresponding locators to the HIP userspace daemon. While the
very useful for avoiding manual configurations. The three components third component is not mandatory, it is very useful for avoiding
are further described in the HIP experiment report [RFC6538]. manual configurations. The three components are further described in
the HIP experiment report [RFC6538].
Based on the interviews, Levae et al suggest further directions to Based on the interviews, Levä et al. suggest further directions to
facilitate HIP deployment. Transitioning a number of HIP facilitate HIP deployment. Transitioning a number of HIP
specifications to the standards track in IETF has already taken specifications to the Standards Track in the IETF has already taken
place, but the authors suggest other additional measures based on the place, but the authors suggest other additional measures based on the
interviews. As a more radical measure, the authors suggest to interviews. As a more radical measure, the authors suggest to
implement HIP as a purely application-layer library [xin-hip-lib] or implement HIP as a purely application-layer library [xin-hip-lib] or
other kind of middleware. On the other hand, more conservative other kind of middleware. On the other hand, more conservative
measures include focusing on private deployments controlled by a measures include focusing on private deployments controlled by a
single stakeholder. As a more concrete example of such a scenario, single stakeholder. As a more concrete example of such a scenario,
HIP could be used by a single service provider to facilitate secure HIP could be used by a single service provider to facilitate secure
connectivity between its servers [komu-cloud]. connectivity between its servers [komu-cloud].
A.3.2. HIP in 802.15.4 networks A.3.2. HIP in 802.15.4 Networks
The IEEE 802 standards have been defining MAC layered security. Many The IEEE 802 standards have been defining MAC-layer security. Many
of these standards use EAP [RFC3748] as a Key Management System (KMS) of these standards use Extensible Authentication Protocol (EAP)
transport, but some like IEEE 802.15.4 [IEEE.802-15-4.2011] leave the [RFC3748] as a Key Management System (KMS) transport, but some like
KMS and its transport as "Out of Scope". IEEE 802.15.4 [IEEE.802.15.4] leave the KMS and its transport as "out
of scope".
HIP is well suited as a KMS in these environments: HIP is well suited as a KMS in these environments:
o HIP is independent of IP addressing and can be directly * HIP is independent of IP addressing and can be directly
transported over any network protocol. transported over any network protocol.
o Master Keys in 802 protocols are commonly pair-based with group * Master keys in 802 protocols are commonly pair-based with group
keys transported from the group controller using pair-wise keys. keys transported from the group controller using pairwise keys.
o AdHoc 802 networks can be better served by a peer-to-peer KMS than * Ad hoc 802 networks can be better served by a peer-to-peer KMS
the EAP client/server model. than the EAP client/server model.
o Some devices are very memory constrained and a common KMS for both * Some devices are very memory constrained, and a common KMS for
MAC and IP security represents a considerable code savings. both MAC and IP security represents a considerable code savings.
A.3.3. HIP and Internet of Things A.3.3. HIP and Internet of Things
HIP requires certain amount computational resources from a device due HIP requires certain amount computational resources from a device due
to cryptographic processing. HIP scales down to phones and small to cryptographic processing. HIP scales down to phones and small
system-on-chip devices (such as Raspberry Pis, Intel Edison), but system-on-chip devices (such as Raspberry Pis, Intel Edison), but
small sensors operating with small batteries have remained small sensors operating with small batteries have remained
problematic. Different extensions to the HIP have been developed to problematic. Different extensions to the HIP have been developed to
scale HIP down to smaller devices, typically with different security scale HIP down to smaller devices, typically with different security
tradeoffs. For example, the non-cryptographic identifiers have been trade-offs. For example, the non-cryptographic identifiers have been
proposed in RFID scenarios. The slimfit approach [hummen] proposes a proposed in RFID scenarios. The Slimfit approach [hummen] proposes a
compression layer for HIP to make it more suitable for constrained compression layer for HIP to make it more suitable for constrained
networks. The approach is applied to a light-weight version of HIP networks. The approach is applied to a lightweight version of HIP
(i.e. "Diet HIP") in order to scale down to small sensors. (i.e., "Diet HIP") in order to scale down to small sensors.
The HIP Diet Exchange [I-D.ietf-hip-dex] design aims at reducing the The HIP Diet EXchange (DEX) [hip-dex] design aims to reduce the
overhead of the employed cryptographic primitives by omitting public- overhead of the employed cryptographic primitives by omitting public-
key signatures and hash functions. In doing so, the main goal is to key signatures and hash functions. In doing so, the main goal is to
still deliver similar security properties to the Base Exchange (BEX). still deliver security properties similar to the Base Exchange (BEX).
DEX is primarily designed for computation or memory- constrained DEX is primarily designed for computation- or memory-constrained
sensor/actuator devices. Like BEX, it is expected to be used sensor/actuator devices. Like BEX, it is expected to be used
together with a suitable security protocol such as the Encapsulated together with a suitable security protocol such as the ESP for the
Security Payload (ESP) for the protection of upper layer protocol protection of upper-layer protocol data. In addition, DEX can also
data. In addition, DEX can also be used as a keying mechanism for be used as a keying mechanism for security primitives at the MAC
security primitives at the MAC layer, e.g., for IEEE 802.15.9 layer, e.g., for IEEE 802.15.9 networks [IEEE.802.15.9].
networks ([IEEE.802-15-9].
The main differences between HIP BEX and DEX are: The main differences between HIP BEX and DEX are:
1. Minimum collection of cryptographic primitives to reduce the 1. Minimum collection of cryptographic primitives to reduce the
protocol overhead. protocol overhead.
* Static Elliptic Curve Diffie-Hellman key pairs for peer * Static Elliptic Curve Diffie-Hellman (ECDH) key pairs for peer
authentication and encryption of the session key. authentication and encryption of the session key.
* AES-CTR for symmetric encryption and AES-CMAC for MACing * AES-CTR for symmetric encryption and AES-CMAC for MACing
function. function.
* A simple fold function for HIT generation. * A simple fold function for HIT generation.
2. Forfeit of Perfect Forward Secrecy with the dropping of an 2. Forfeit of perfect forward secrecy with the dropping of an
ephemeral Diffie-Hellman key agreement. ephemeral Diffie-Hellman key agreement.
3. Forfeit of digital signatures with the removal of a hash 3. Forfeit of digital signatures with the removal of a hash
function. Reliance on ECDH derived key used in HIP_MAC to prove function. Reliance on the ECDH-derived key used in HIP_MAC to
ownership of the private key. prove ownership of the private key.
4. Diffie-Hellman derived key ONLY used to protect the HIP packets. 4. Diffie-Hellman derived key ONLY used to protect the HIP packets.
A separate secret exchange within the HIP packets creates the A separate secret exchange within the HIP packets creates the
session key(s). session key(s).
5. Optional retransmission strategy tailored to handle the 5. Optional retransmission strategy tailored to handle the
potentially extensive processing time of the employed potentially extensive processing time of the employed
cryptographic operations on computationally constrained devices. cryptographic operations on computationally constrained devices.
A.3.4. Infrastructure Applications A.3.4. Infrastructure Applications
HIP experimentation report [RFC6538] enumerates a number of client The HIP experimentation report [RFC6538] enumerates a number of
and server applications that have been trialed with HIP. Based on client and server applications that have been trialed with HIP.
the report, this section highlights and complements some potential Based on the report, this section highlights and complements some
ways how HIP could be exploited in existing infrastructure such as potential ways how HIP could be exploited in existing infrastructure
routers, gateways and proxies. such as routers, gateways, and proxies.
HIP has been successfully used with forward web proxies (i.e., HIP has been successfully used with forward web proxies (i.e.,
client-side proxies). HIP was used between a client host (web client-side proxies). HIP was used between a client host (web
browser) and a forward proxy (Apache server) that terminated the HIP/ browser) and a forward proxy (Apache server) that terminated the HIP/
ESP-tunnel. The forward web proxy translated HIP-based traffic ESP tunnel. The forward web proxy translated HIP-based traffic
originating from the client into non-HIP traffic towards any web originating from the client into non-HIP traffic towards any web
server in the Internet. Consequently, the HIP-capable client could server in the Internet. Consequently, the HIP-capable client could
communicate with HIP-incapable web servers. This way, the client communicate with HIP-incapable web servers. This way, the client
could utilize mobility support as provided by HIP while using the could utilize mobility support as provided by HIP while using the
fixed IP address of the web proxy, for instance, to access services fixed IP address of the web proxy, for instance, to access services
that were allowed only from the IP address range of the proxy. that were allowed only from the IP address range of the proxy.
HIP has also been experimented with reverse web proxies (i.e. server- HIP with reverse web proxies (i.e., server-side proxies) has also
side proxies) as described in more detail in [komu-cloud]. In this been investigated, as described in more detail in [komu-cloud]. In
scenario, a HIP-incapable client accessed a HIP-capable web service this scenario, a HIP-incapable client accessed a HIP-capable web
via an intermediary load balancer (that was a web based load balancer service via an intermediary load balancer (a web-based load balancer
implementation called HAProxy). The load balancer translated non-HIP implementation called HAProxy). The load balancer translated non-HIP
traffic originating from the client into HIP-based traffic for the traffic originating from the client into HIP-based traffic for the
web service (consisting of front-end and back-end servers). Both the web service (consisting of front-end and back-end servers). Both the
load balancer and the web service were located in a datacenter. One load balancer and the web service were located in a data center. One
of the key benefits for encrypting the web traffic with HIP in this of the key benefits for encrypting the web traffic with HIP in this
scenario was to support a private-public cloud scenario (i.e. hybrid scenario was supporting a private-public cloud scenario (i.e., hybrid
cloud) where the load balancer, front-end servers and back-end cloud) where the load balancer, front-end servers, and back-end
servers can be located in different datacenters and, thus, the servers were located in different data centers, and thus the traffic
traffic needs to protected when it passes through potentially needed to be protected when it passed through potentially insecure
insecure networks between the borders of the private and public networks between the borders of the private and public clouds.
clouds.
While HIP could be used to secure access to intermediary devices While HIP could be used to secure access to intermediary devices
(e.g., access to switches with legacy telnet), it has also been used (e.g., access to switches with legacy telnet), it has also been used
to secure intermittent connectivity between middlebox infrastructure. to secure intermittent connectivity between middlebox infrastructure.
For instance, earlier research [komu-mitigation] utilized HIP between For instance, earlier research [komu-mitigation] utilized HIP between
Secure Mail Transport Protocol (SMTP) servers in order to exploit the Simple Mail Transport Protocol (SMTP) servers in order to exploit the
computational puzzles of HIP as a spam mitigation mechanism. A computational puzzles of HIP as a spam mitigation mechanism. A
rather obvious practical challenge in this approach was the lack of rather obvious practical challenge in this approach was the lack of
HIP adoption on existing SMTP servers. HIP adoption on existing SMTP servers.
To avoid deployment hurdles with existing infrastructure, HIP could To avoid deployment hurdles with existing infrastructure, HIP could
be applied in the context of new protocols with little deployment. be applied in the context of new protocols with little deployment.
Namely, HIP has been experimented in the context of a new protocol, Namely, HIP has been studied in the context of a new protocol, peer-
peer-to-peer SIP [camarillo-p2psip]. The work has resulted in a to-peer SIP [camarillo-p2psip]. The work has resulted in a number of
number of related RFCs [RFC6078], [RFC6079], [RFC7086]. The key idea related RFCs [RFC6078], [RFC6079], and [RFC7086]. The key idea in
in the research work was to avoid redundant, time consuming ICE the research work was to avoid redundant, time-consuming ICE
procedures by grouping different connections (i.e. SIP and media procedures by grouping different connections (i.e., SIP and media
streams) together using the low-layer HIP which executes NAT streams) together using the low-layer HIP, which executes NAT
traversal procedures only once per host. An interesting aspect in traversal procedures only once per host. An interesting aspect in
the approach was the use of P2P-SIP infrastructure as rendezvous the approach was the use of P2P-SIP infrastructure as rendezvous
servers for HIP control plane instead of utilizing the traditional servers for the HIP control plane instead of utilizing the
HIP rendezvous services [RFC8004]. traditional HIP rendezvous services [RFC8004].
Researchers have proposed to use HIP in cellular networks as a Researchers have proposed using HIP in cellular networks as a
mobility, multihoming and security solution. [hip-lte] provides a mobility, multihoming, and security solution. [hip-lte] provides a
security analysis and simulation measurements of using HIP in Long security analysis and simulation measurements of using HIP in Long
Term Evolution (LTE) backhaul networks. Term Evolution (LTE) backhaul networks.
HIP has been experimented with securing cloud internal connectivity. HIP has been studied for securing cloud internal connectivity. First
First with virtual machines [komu-cloud] and then later also between with virtual machines [komu-cloud] and then between Linux containers
Linux containers [ranjbar-synaptic]. In both cases, HIP was [ranjbar-synaptic]. In both cases, HIP was suggested as a solution
suggested as a solution NAT traversal that could be utilized both to NAT traversal that could be utilized both internally by a cloud
internally by a cloud network and between multi-cloud deployments. network and between multi-cloud deployments. Specifically in the
Specifically in the former case, HIP was beneficial sustaining former case, HIP was beneficial sustaining connectivity with a
connectivity with a virtual machine while it migrates to a new virtual machine while it migrated to a new location. In the latter
location. In the latter case, Software-Defined Networking (SDN) case, a Software-Defined Networking (SDN) controller acted as a
controller acted as rendezvous server for HIP-capable containers. rendezvous server for HIP-capable containers. The controller
The controller enforced strong replay protection by adding middlebox enforced strong replay protection by adding middlebox nonces
nonces [heer-end-host] to the passing HIP base exchange and UPDATE [heer-end-host] to the passing HIP base exchange and UPDATE messages.
messages.
A.3.5. Management of Identities in a Commercial Product A.3.5. Management of Identities in a Commercial Product
Tempered Networks provides HIP-based products. They refer to their Tempered Networks provides HIP-based products. They refer to their
platform as Identity-Defined Networking (IDN) [tempered-networks] platform as Identity-Defined Networking (IDN) [tempered-networks]
because of HIP's identity-first networking architecture. Their because of HIP's identity-first networking architecture. Their
objective has been to make it simple and non-disruptive to deploy HIP objective has been to make it simple and nondisruptive to deploy HIP-
enabled services widely in production environments with the purpose enabled services widely in production environments with the purpose
of enabling transparent device authentication and authorization, of enabling transparent device authentication and authorization,
cloaking, segmentation, and end-to-end networking. The goal is to cloaking, segmentation, and end-to-end networking. The goal is to
eliminate much of the circular dependencies, exploits, and layered eliminate much of the circular dependencies, exploits, and layered
complexity of traditional "address-defined networking" that prevents complexity of traditional "address-defined networking" that prevents
mobility and verifiable device access control. The products in the mobility and verifiable device access control. The products in the
portfolio of Tempered Networks utilize HIP as follows: portfolio of Tempered Networks utilize HIP are as follows:
o HIP Switches / Gateways - these are physical or virtual appliances HIP Switches / Gateways
that serve as the HIP gateway and policy enforcement point for non These are physical or virtual appliances that serve as the HIP
HIP-aware applications and devices located behind it. No IP or gateway and policy enforcement point for non-HIP-aware
applications and devices located behind it. No IP or
infrastructure changes are required in order to connect, cloak, infrastructure changes are required in order to connect, cloak,
and protect the non-HIP aware devices. Currently known supported and protect the non-HIP-aware devices. Currently known supported
platforms for HIP gateways are: x86 and ARM chipsets, ESXi, Hyper- platforms for HIP gateways are x86 and ARM chipsets, ESXi, Hyper-
V, KVM, AWS, Azure, and Google clouds. V, KVM, AWS, Azure, and Google clouds.
o HIP Relays / Rendezvous - are physical or virtual appliances that HIP Relays / Rendezvous
serve as identity based routers authorizing and bridging HIP These are physical or virtual appliances that serve as identity-
endpoints without decrypting the HIP session. A HIP Relay can be based routers authorizing and bridging HIP endpoints without
deployed as a standalone appliance or in a cluster for horizontal decrypting the HIP session. A HIP relay can be deployed as a
scaling. All HIP aware endpoints and the devices they're standalone appliance or in a cluster for horizontal scaling. All
connecting and protecting can remain privately addressed, The HIP-aware endpoints and the devices they're connecting and
appliances eliminate IP conflicts, tunnel through NAT and CGNAT, protecting can remain privately addressed. The appliances
and require no changes to the underlay infrastructure. The only eliminate IP conflicts, tunnel through NAT and carrier-grade NAT,
and require no changes to the underlying infrastructure. The only
requirement is that a HIP endpoint should have outbound access to requirement is that a HIP endpoint should have outbound access to
the Internet and that a HIP Relay should have a public address. the Internet and that a HIP Relay should have a public address.
o HIP-Aware Clients and Servers - software that installs in the HIP-Aware Clients and Servers
host's network stack and enforces policy for that host. HIP This is software that is installed in the host's network stack and
clients support split tunneling. Both HIP client and HIP server enforces policy for that host. HIP clients support split
can interface with the local host firewall and HIP Server can be tunneling. Both the HIP client and HIP server can interface with
locked down to listen only on the port used for HIP, making the the local host firewall, and the HIP server can be locked down to
server invisible from unauthorized devices. Currently known listen only on the port used for HIP, making the server invisible
supported platforms are Windows, OSX, iOS, Android, Ubuntu, CentOS from unauthorized devices. Currently known supported platforms
and other Linux derivatives. are Windows, OS X, iOS, Android, Ubuntu, CentOS, and other Linux
derivatives.
o Policy Orchestration Managers - a physical or virtual appliance Policy Orchestration Managers
that serves as the engine to define and distribute network and These physical or virtual appliances serve as the engine to define
security policy (HI and IP mappings, overlay networks and and distribute network and security policy (HI and IP mappings,
whitelist policies etc.) to HIP-aware endpoints. Orchestration overlay networks, and whitelist policies, etc.) to HIP-aware
does not need to persist to the HIP endpoints and vice versa endpoints. Orchestration does not need to persist to the HIP
allowing for autonomous host networking and security. endpoints and vice versa, allowing for autonomous host networking
and security.
A.4. Answers to NSRG questions A.4. Answers to NSRG Questions
The IRTF Name Space Research Group has posed a number of evaluating The IRTF Name Space Research Group has posed a number of evaluating
questions in their report [nsrg-report]. In this section, we provide questions in their report [nsrg-report]. In this section, we provide
answers to these questions. answers to these questions.
1. How would a stack name improve the overall functionality of the 1. How would a stack name improve the overall functionality of the
Internet? Internet?
HIP decouples the internetworking layer from the transport HIP decouples the internetworking layer from the transport layer,
layer, allowing each to evolve separately. The decoupling allowing each to evolve separately. The decoupling makes end-
makes end-host mobility and multi-homing easier, also across host mobility and multihoming easier, also across IPv4 and IPv6
IPv4 and IPv6 networks. HIs make network renumbering easier, networks. HIs make network renumbering easier, and they also
and they also make process migration and clustered servers make process migration and clustered servers easier to implement.
easier to implement. Furthermore, being cryptographic in Furthermore, being cryptographic in nature, they provide the
nature, they provide the basis for solving the security basis for solving the security problems related to end-host
problems related to end-host mobility and multi-homing. mobility and multihoming.
2. What does a stack name look like? 2. What does a stack name look like?
A HI is a cryptographic public key. However, instead of using
the keys directly, most protocols use a fixed-size hash of the A HI is a cryptographic public key. However, instead of using
public key. the keys directly, most protocols use a fixed-size hash of the
public key.
3. What is its lifetime? 3. What is its lifetime?
HIP provides both stable and temporary Host Identifiers. HIP provides both stable and temporary Host Identifiers. Stable
Stable HIs are typically long-lived, with a lifetime of years HIs are typically long-lived, with a lifetime of years or more.
or more. The lifetime of temporary HIs depends on how long The lifetime of temporary HIs depends on how long the upper-layer
the upper-layer connections and applications need them, and connections and applications need them, and can range from a few
can range from a few seconds to years. seconds to years.
4. Where does it live in the stack? 4. Where does it live in the stack?
The HIs live between the transport and internetworking layers. The HIs live between the transport and internetworking layers.
5. How is it used on the end points? 5. How is it used on the endpoints?
The Host Identifiers may be used directly or indirectly (in The Host Identifiers may be used directly or indirectly (in the
the form of HITs or LSIs) by applications when they access form of HITs or LSIs) by applications when they access network
network services. Additionally, the Host Identifiers, as services. Additionally, the Host Identifiers, as public keys,
public keys, are used in the built-in key agreement protocol, are used in the built-in key agreement protocol, called the HIP
called the HIP base exchange, to authenticate the hosts to base exchange, to authenticate the hosts to each other.
each other.
6. What administrative infrastructure is needed to support it? 6. What administrative infrastructure is needed to support it?
In some environments, it is possible to use HIP In some environments, it is possible to use HIP
opportunistically, without any infrastructure. However, to opportunistically, without any infrastructure. However, to gain
gain full benefit from HIP, the HIs must be stored in the DNS full benefit from HIP, the HIs must be stored in the DNS or a
or a PKI, and the rendezvous mechanism is needed [RFC8005]. PKI, and the rendezvous mechanism is needed [RFC8005].
7. If we add an additional layer would it make the address list in 7. If we add an additional layer, would it make the address list in
SCTP unnecessary? SCTP unnecessary?
Yes Yes
8. What additional security benefits would a new naming scheme 8. What additional security benefits would a new naming scheme
offer? offer?
HIP reduces dependency on IP addresses, making the so-called HIP reduces dependency on IP addresses, making the so-called
address ownership [Nik2001] problems easier to solve. In address ownership [Nik2001] problems easier to solve. In
practice, HIP provides security for end-host mobility and practice, HIP provides security for end-host mobility and
multi-homing. Furthermore, since HIP Host Identifiers are multihoming. Furthermore, since HIP Host Identifiers are public
public keys, standard public key certificate infrastructures keys, standard public key certificate infrastructures can be
can be applied on the top of HIP. applied on the top of HIP.
9. What would the resolution mechanisms be, or what characteristics 9. What would the resolution mechanisms be, or what characteristics
of a resolution mechanisms would be required? of a resolution mechanisms would be required?
For most purposes, an approach where DNS names are resolved For most purposes, an approach where DNS names are resolved
simultaneously to HIs and IP addresses is sufficient. simultaneously to HIs and IP addresses is sufficient. However,
However, if it becomes necessary to resolve HIs into IP if it becomes necessary to resolve HIs into IP addresses or back
addresses or back to DNS names, a flat resolution to DNS names, a flat resolution infrastructure is needed. Such
infrastructure is needed. Such an infrastructure could be an infrastructure could be based on the ideas of Distributed Hash
based on the ideas of Distributed Hash Tables, but would Tables, but would require significant new development and
require significant new development and deployment. deployment.
Acknowledgments
For the people historically involved in the early stages of HIP, see
the Acknowledgments section in the Host Identity Protocol
specification.
During the later stages of this document, when the editing baton was
transferred to Pekka Nikander, the comments from the early
implementers and others, including Jari Arkko, Jeff Ahrenholz, Tom
Henderson, Petri Jokela, Miika Komu, Mika Kousa, Andrew McGregor, Jan
Melen, Tim Shepard, Jukka Ylitalo, Sasu Tarkoma, and Jorma Wall, were
invaluable. Also, the comments from Lars Eggert, Spencer Dawkins,
Dave Crocker, and Erik Giesa were also useful.
The authors want to express their special thanks to Tom Henderson,
who took the burden of editing the document in response to IESG
comments at the time when both of the authors were busy doing other
things. Without his perseverance, the original document might have
never made it as RFC 4423.
This main effort to update and move HIP forward within the IETF
process owes its impetus to a number of HIP development teams. The
authors are grateful for Boeing, Helsinki Institute for Information
Technology (HIIT), NomadicLab of Ericsson, and the three
universities: RWTH Aachen, Aalto, and University of Helsinki for
their efforts. Without their collective efforts, HIP would have
withered as on the IETF vine as a nice concept.
Thanks also to Suvi Koskinen for her help with proofreading and with
the reference jungle.
Authors' Addresses Authors' Addresses
Robert Moskowitz (editor) Robert Moskowitz (editor)
HTT Consulting HTT Consulting
Oak Park Oak Park, Michigan
Michigan United States of America
USA
Email: rgm@labs.htt-consult.com Email: rgm@labs.htt-consult.com
Miika Komu Miika Komu
Ericsson Ericsson
Hirsalantie 11 Hirsalantie 11
02420 Jorvas FI-02420 Jorvas
Finland Finland
Email: miika.komu@ericsson.com Email: miika.komu@ericsson.com
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