draft-ietf-ipsecme-rfc4307bis-07.txt   draft-ietf-ipsecme-rfc4307bis-08.txt 
Network Working Group Y. Nir Network Working Group Y. Nir
Internet-Draft Check Point Internet-Draft Check Point
Obsoletes: 4307 (if approved) T. Kivinen Obsoletes: 4307 (if approved) T. Kivinen
Updates: 7296 (if approved) INSIDE Secure Updates: 7296 (if approved) INSIDE Secure
Intended status: Standards Track P. Wouters Intended status: Standards Track P. Wouters
Expires: October 09, 2016 Red Hat Expires: November 12, 2016 Red Hat
D. Migault D. Migault
Ericsson Ericsson
April 07, 2016 May 11, 2016
Algorithm Implementation Requirements and Usage Guidance for IKEv2 Algorithm Implementation Requirements and Usage Guidance for IKEv2
draft-ietf-ipsecme-rfc4307bis-07 draft-ietf-ipsecme-rfc4307bis-08
Abstract Abstract
The IPsec series of protocols makes use of various cryptographic The IPsec series of protocols makes use of various cryptographic
algorithms in order to provide security services. The Internet Key algorithms in order to provide security services. The Internet Key
Exchange (IKE) protocol is used to negotiate the IPsec Security Exchange (IKE) protocol is used to negotiate the IPsec Security
Association (IPsec SA) parameters, such as which algorithms should be Association (IPsec SA) parameters, such as which algorithms should be
used. To ensure interoperability between different implementations, used. To ensure interoperability between different implementations,
it is necessary to specify a set of algorithm implementation it is necessary to specify a set of algorithm implementation
requirements and usage guidance to ensure that there is at least one requirements and usage guidance to ensure that there is at least one
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 09, 2016. This Internet-Draft will expire on November 12, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Updating Algorithm Implementation Requirements and Usage 1.1. Updating Algorithm Implementation Requirements and Usage
Guidance . . . . . . . . . . . . . . . . . . . . . . . . 3 Guidance . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Updating Algorithm Requirement Levels . . . . . . . . . . 3 1.2. Updating Algorithm Requirement Levels . . . . . . . . . . 3
1.3. Document Audience . . . . . . . . . . . . . . . . . . . . 4 1.3. Document Audience . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 4 2. Conventions Used in This Document . . . . . . . . . . . . . . 4
3. Algorithm Selection . . . . . . . . . . . . . . . . . . . . . 5 3. Algorithm Selection . . . . . . . . . . . . . . . . . . . . . 5
3.1. Type 1 - IKEv2 Encryption Algorithm Transforms . . . . . 5 3.1. Type 1 - IKEv2 Encryption Algorithm Transforms . . . . . 5
3.2. Type 2 - IKEv2 Pseudo-random Function Transforms . . . . 7 3.2. Type 2 - IKEv2 Pseudo-random Function Transforms . . . . 6
3.3. Type 3 - IKEv2 Integrity Algorithm Transforms . . . . . . 8 3.3. Type 3 - IKEv2 Integrity Algorithm Transforms . . . . . . 7
3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms . . . . . 9 3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms . . . . . 8
4. IKEv2 Authentication . . . . . . . . . . . . . . . . . . . . 10 4. IKEv2 Authentication . . . . . . . . . . . . . . . . . . . . 10
4.1. IKEv2 Authentication Method . . . . . . . . . . . . . . . 10 4.1. IKEv2 Authentication Method . . . . . . . . . . . . . . . 10
4.1.1. Recommendations for RSA key length . . . . . . . . . 11 4.1.1. Recommendations for RSA key length . . . . . . . . . 11
4.2. Digital Signature Recommendations . . . . . . . . . . . . 11 4.2. Digital Signature Recommendations . . . . . . . . . . . . 11
5. Algorithms for Internet of Things . . . . . . . . . . . . . . 12 5. Algorithms for Internet of Things . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . 14 9.1. Normative References . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . 14 9.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
The Internet Key Exchange (IKE) protocol [RFC7296] is used to The Internet Key Exchange (IKE) protocol [RFC7296] is used to
negotiate the parameters of the IPsec SA, such as the encryption and negotiate the parameters of the IPsec SA, such as the encryption and
authentication algorithms and the keys for the protected authentication algorithms and the keys for the protected
communications between the two endpoints. The IKE protocol itself is communications between the two endpoints. The IKE protocol itself is
also protected by cryptographic algorithms which are negotiated also protected by cryptographic algorithms which are negotiated
between the two endpoints using IKE. Different implementations of between the two endpoints using IKE. Different implementations of
IKE may negotiate different algorithms based on their individual IKE may negotiate different algorithms based on their individual
local policy. To ensure interoperability, a set of "mandatory-to- local policy. To ensure interoperability, a set of "mandatory-to-
implement" IKE cryptographic algorithms is defined. implement" IKE cryptographic algorithms is defined.
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algorithms for future mandatory-to-implement status. There is no algorithms for future mandatory-to-implement status. There is no
guarantee that the algorithms in use today may become mandatory in guarantee that the algorithms in use today may become mandatory in
the future. Published algorithms are continuously subjected to the future. Published algorithms are continuously subjected to
cryptographic attack and may become too weak or could become cryptographic attack and may become too weak or could become
completely broken before this document is updated. completely broken before this document is updated.
This document only provides recommendations for the mandatory-to- This document only provides recommendations for the mandatory-to-
implement algorithms or algorithms too weak that are recommended not implement algorithms or algorithms too weak that are recommended not
to be implemented. As a result, any algorithm listed at the IKEv2 to be implemented. As a result, any algorithm listed at the IKEv2
IANA registry not mentioned in this document MAY be implemented. For IANA registry not mentioned in this document MAY be implemented. For
clarification and consistency with [RFC4307] an algorithm will be set clarification and consistency with [RFC4307] an algorithm will be
to MAY only when it has been downgraded. denoted here as MAY only when it has been downgraded.
Although this document updates the algorithms to keep the IKEv2 Although this document updates the algorithms to keep the IKEv2
communication secure over time, it also aims at providing communication secure over time, it also aims at providing
recommendations so that IKEv2 implementations remain interoperable. recommendations so that IKEv2 implementations remain interoperable.
IKEv2 interoperability is addressed by an incremental introduction or IKEv2 interoperability is addressed by an incremental introduction or
deprecation of algorithms. In addition, this document also considers deprecation of algorithms. In addition, this document also considers
the new use cases for IKEv2 deployment, such as Internet of Things the new use cases for IKEv2 deployment, such as Internet of Things
(IoT). (IoT).
It is expected that deprecation of an algorithm is performed It is expected that deprecation of an algorithm is performed
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Similarly, an algorithm that has not been mentioned as mandatory-to- Similarly, an algorithm that has not been mentioned as mandatory-to-
implement is expected to be introduced with a SHOULD instead of a implement is expected to be introduced with a SHOULD instead of a
MUST. MUST.
The current trend toward Internet of Things and its adoption of IKEv2 The current trend toward Internet of Things and its adoption of IKEv2
requires this specific use case to be taken into account as well. requires this specific use case to be taken into account as well.
IoT devices are resource constrained devices and their choice of IoT devices are resource constrained devices and their choice of
algorithms are motivated by minimizing the footprint of the code, the algorithms are motivated by minimizing the footprint of the code, the
computation effort and the size of the messages to send. This computation effort and the size of the messages to send. This
document indicates "[IoT]" when a specified algorithm is specifically document indicates "[IoT]" when a specified algorithm is specifically
listed for IoT devices. listed for IoT devices. Requirement levels that are marked as "IoT"
apply to IoT devices and to server-side implementations that might
presumably need to interoperate with them, including any general-
purpose VPN gateways.
1.3. Document Audience 1.3. Document Audience
The recommendations of this document mostly target IKEv2 implementers The recommendations of this document mostly target IKEv2 implementers
as implementations need to meet both high security expectations as as implementations need to meet both high security expectations as
well as high interoperability between various vendors and with well as high interoperability between various vendors and with
different versions. Interoperability requires a smooth move to more different versions. Interoperability requires a smooth move to more
secure cipher suites. This may differ from a user point of view that secure cipher suites. This may differ from a user point of view that
may deploy and configure IKEv2 with only the safest cipher suite. On may deploy and configure IKEv2 with only the safest cipher suite. On
the other hand, comments and recommendations from this document are the other hand, comments from this document are also expected to be
also expected to be useful for such users. useful for such users.
IKEv1 is out of scope of this document. IKEv1 is deprecated and the IKEv1 is out of scope of this document. IKEv1 is deprecated and the
recommendations of this document must not be considered for IKEv1, as recommendations of this document must not be considered for IKEv1, as
most IKEv1 implementations have been "frozen" and will not be able to most IKEv1 implementations have been "frozen" and will not be able to
update the list of mandatory-to-implement algorithms. update the list of mandatory-to-implement algorithms.
2. Conventions Used in This Document 2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
We define some additional terms here: We define some additional terms here:
SHOULD+ This term means the same as SHOULD. However, it is likely SHOULD+ This term means the same as SHOULD. However, it is likely
that an algorithm marked as SHOULD+ will be promoted at some that an algorithm marked as SHOULD+ will be promoted at
future time to be a MUST. some future time to be a MUST.
SHOULD- This term means the same as SHOULD. However, an algorithm SHOULD- This term means the same as SHOULD. However, an algorithm
marked as SHOULD- may be deprecated to a MAY in a future marked as SHOULD- may be deprecated to a MAY in a future
version of this document. version of this document.
MUST- This term means the same as MUST. However, we expect at some MUST- This term means the same as MUST. However, we expect at
point that this algorithm will no longer be a MUST in a some point that this algorithm will no longer be a MUST in
future document. Although its status will be determined at a a future document. Although its status will be determined
later time, it is reasonable to expect that if a future at a later time, it is reasonable to expect that if a
revision of a document alters the status of a MUST- future revision of a document alters the status of a MUST-
algorithm, it will remain at least a SHOULD or a SHOULD- algorithm, it will remain at least a SHOULD or a SHOULD-
level. level.
IoT stands for Internet of Things. IoT stands for Internet of Things.
Table 1
3. Algorithm Selection 3. Algorithm Selection
3.1. Type 1 - IKEv2 Encryption Algorithm Transforms 3.1. Type 1 - IKEv2 Encryption Algorithm Transforms
The algorithms in the below table are negotiated in the SA payload The algorithms in the below table are negotiated in the SA payload
and used for the Encrypted Payload. References to the specification and used for the Encrypted Payload. References to the specification
defining these algorithms and the ones in the following subsections defining these algorithms and the ones in the following subsections
are in the IANA registry [IKEV2-IANA]. Some of these algorithms are are in the IANA registry [IKEV2-IANA]. Some of these algorithms are
Authenticated Encryption with Associated Data (AEAD - [RFC5282]). Authenticated Encryption with Associated Data (AEAD - [RFC5282]).
Algorithms that are not AEAD MUST be used in conjunction with an Algorithms that are not AEAD MUST be used in conjunction with an
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| AES-GCM with a 16 octet ICV | SHOULD | Yes | [1] | | AES-GCM with a 16 octet ICV | SHOULD | Yes | [1] |
| ENCR_AES_CCM_8 | SHOULD | Yes | [1][IoT] | | ENCR_AES_CCM_8 | SHOULD | Yes | [1][IoT] |
| ENCR_3DES | MAY | No | | | ENCR_3DES | MAY | No | |
| ENCR_DES | MUST NOT | No | | | ENCR_DES | MUST NOT | No | |
+-----------------------------+----------+-------+----------+ +-----------------------------+----------+-------+----------+
[1] - This requirement level is for 128-bit keys. 256-bit keys are at [1] - This requirement level is for 128-bit keys. 256-bit keys are at
SHOULD. 192-bit keys can safely be ignored. [IoT] - This requirement SHOULD. 192-bit keys can safely be ignored. [IoT] - This requirement
is for interoperability with IoT. is for interoperability with IoT.
Table 2
ENCR_AES_CBC is raised from SHOULD+ in [RFC4307] to MUST. It is the ENCR_AES_CBC is raised from SHOULD+ in [RFC4307] to MUST. It is the
only shared mandatory-to-implement algorithm with RFC4307 and as a only shared mandatory-to-implement algorithm with RFC4307 and as a
result it is necessary for interoperability with IKEv2 implementation result it is necessary for interoperability with IKEv2 implementation
compatible with RFC4307. compatible with RFC4307.
ENCR_CHACHA20_POLY1305 was not ready to be considered at the time of ENCR_CHACHA20_POLY1305 was not ready to be considered at the time of
RFC4307. It has been recommended by the CRFG and others as an RFC4307. It has been recommended by the CRFG and others as an
alternative to AES-CBC and AES-GCM. It is also being standardized alternative to AES-CBC and AES-GCM. It is also being standardized
for IPsec for the same reasons. At the time of writing, there were for IPsec for the same reasons. At the time of writing, there were
not enough IKEv2 implementations supporting ENCR_CHACHA20_POLY1305 to not enough IKEv2 implementations supporting ENCR_CHACHA20_POLY1305 to
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+-------------------+----------+---------+ +-------------------+----------+---------+
| PRF_HMAC_SHA2_256 | MUST | | | PRF_HMAC_SHA2_256 | MUST | |
| PRF_HMAC_SHA2_512 | SHOULD+ | | | PRF_HMAC_SHA2_512 | SHOULD+ | |
| PRF_HMAC_SHA1 | MUST- | | | PRF_HMAC_SHA1 | MUST- | |
| PRF_AES128_XCBC | SHOULD | [IoT] | | PRF_AES128_XCBC | SHOULD | [IoT] |
| PRF_HMAC_MD5 | MUST NOT | | | PRF_HMAC_MD5 | MUST NOT | |
+-------------------+----------+---------+ +-------------------+----------+---------+
[IoT] - This requirement is for interoperability with IoT [IoT] - This requirement is for interoperability with IoT
Table 3
PRF_HMAC_SHA2_256 was not mentioned in RFC4307, as no SHA2 based PRF_HMAC_SHA2_256 was not mentioned in RFC4307, as no SHA2 based
transforms were mentioned. PRF_HMAC_SHA2_256 MUST be implemented in transforms were mentioned. PRF_HMAC_SHA2_256 MUST be implemented in
order to replace SHA1 and PRF_HMAC_SHA1. order to replace SHA1 and PRF_HMAC_SHA1.
PRF_HMAC_SHA2_512 SHOULD be implemented as a future replacement for PRF_HMAC_SHA2_512 SHOULD be implemented as a future replacement for
PRF_HMAC_SHA2_256 or when stronger security is required. PRF_HMAC_SHA2_256 or when stronger security is required.
PRF_HMAC_SHA2_512 is preferred over PRF_HMAC_SHA2_384, as the PRF_HMAC_SHA2_512 is preferred over PRF_HMAC_SHA2_384, as the
additional overhead of PRF_HMAC_SHA2_512 is negligible. additional overhead of PRF_HMAC_SHA2_512 is negligible.
PRF_HMAC_SHA1 has been downgraded from MUST in RFC4307 to MUST- as PRF_HMAC_SHA1 has been downgraded from MUST in RFC4307 to MUST- as
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| AUTH_HMAC_SHA2_512_256 | SHOULD | | | AUTH_HMAC_SHA2_512_256 | SHOULD | |
| AUTH_HMAC_SHA1_96 | MUST- | | | AUTH_HMAC_SHA1_96 | MUST- | |
| AUTH_AES_XCBC_96 | SHOULD | [IoT] | | AUTH_AES_XCBC_96 | SHOULD | [IoT] |
| AUTH_HMAC_MD5_96 | MUST NOT | | | AUTH_HMAC_MD5_96 | MUST NOT | |
| AUTH_DES_MAC | MUST NOT | | | AUTH_DES_MAC | MUST NOT | |
| AUTH_KPDK_MD5 | MUST NOT | | | AUTH_KPDK_MD5 | MUST NOT | |
+------------------------+----------+---------+ +------------------------+----------+---------+
[IoT] - This requirement is for interoperability with IoT [IoT] - This requirement is for interoperability with IoT
Table 4
AUTH_HMAC_SHA2_256_128 was not mentioned in RFC4307, as no SHA2 based AUTH_HMAC_SHA2_256_128 was not mentioned in RFC4307, as no SHA2 based
transforms were mentioned. AUTH_HMAC_SHA2_256_128 MUST be transforms were mentioned. AUTH_HMAC_SHA2_256_128 MUST be
implemented in order to replace AUTH_HMAC_SHA1_96. implemented in order to replace AUTH_HMAC_SHA1_96.
AUTH_HMAC_SHA2_512_256 SHOULD be implemented as a future replacement AUTH_HMAC_SHA2_512_256 SHOULD be implemented as a future replacement
of AUTH_HMAC_SHA2_256_128 or when stronger security is required. of AUTH_HMAC_SHA2_256_128 or when stronger security is required.
This value has been preferred over AUTH_HMAC_SHA2_384, as the This value has been preferred over AUTH_HMAC_SHA2_384, as the
additional overhead of AUTH_HMAC_SHA2_512 is negligible. additional overhead of AUTH_HMAC_SHA2_512 is negligible.
AUTH_HMAC_SHA1_96 has been downgraded from MUST in RFC4307 to MUST- AUTH_HMAC_SHA1_96 has been downgraded from MUST in RFC4307 to MUST-
as there is an industry-wide trend to deprecate its usage. as there is an industry-wide trend to deprecate its usage.
AUTH_AES-XCBC is only recommended in the scope of IoT, as Internet of AUTH_AES-XCBC is only recommended in the scope of IoT, as Internet of
Things deployments tend to prefer AES based pseudo-random functions Things deployments tend to prefer AES based pseudo-random functions
in order to avoid implementing SHA2. For the non-IoT VPN deployment, in order to avoid implementing SHA2. For the non-IoT VPN deployment,
it has been downgraded from SHOULD in RFC4307 to MAY as it has not it has been downgraded from SHOULD in RFC4307 to MAY as it has not
been widely adopted. been widely adopted.
AUTH_HMAC_MD5_96, AUTH_DES_MAC and AUTH_KPDK_MD5 were not mentioned AUTH_DES_MAC, AUTH_HMAC_MD5_96, and AUTH_KPDK_MD5 were not mentioned
in RFC4307 so its default status was MAY. It has been downgraded to in RFC4307 so their default status ware MAY. They have been
MUST NOT. There is an industry-wide trend to deprecate its usage. downgraded to MUST NOT. There is an industry-wide trend to deprecate
DES and MD5. MD5 support is being removed from cryptographic
MD5 support is being removed from cryptographic libraries in general libraries in general because its non-HMAC use is known to be subject
because its non-HMAC use is known to be subject to collision attacks, to collision attacks, for example as mentioned in [TRANSCRIPTION].
for example as mentioned in [TRANSCRIPTION].
3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms 3.4. Type 4 - IKEv2 Diffie-Hellman Group Transforms
There are several Modular Exponential (MODP) groups and several There are several Modular Exponential (MODP) groups and several
Elliptic Curve groups (ECC) that are defined for use in IKEv2. These Elliptic Curve groups (ECC) that are defined for use in IKEv2. These
groups are defined in both the [IKEv2] base document and in groups are defined in both the [IKEv2] base document and in
extensions documents and are identified by group number. Note that extensions documents and are identified by group number. Note that
it is critical to enforce a secure Diffie-Hellman exchange as this it is critical to enforce a secure Diffie-Hellman exchange as this
exchange provides keys for the session. If an attacker can retrieve exchange provides keys for the session. If an attacker can retrieve
the private numbers (a, or b) and the public values (g**a, and g**b), the private numbers (a, or b) and the public values (g**a, and g**b),
then the attacker can compute the secret and the keys used and then the attacker can compute the secret and the keys used and
decrypt the exchange and IPsec SA created inside the IKEv2 SA. Such decrypt the exchange and IPsec SA created inside the IKEv2 SA. Such
an attack can be performed off-line on a previously recorded an attack can be performed off-line on a previously recorded
communication, years after the communication happened. This differs communication, years after the communication happened. This differs
from attacks that need to be executed during the authentication which from attacks that need to be executed during the authentication which
must be performed online and in near real-time. must be performed online and in near real-time.
+------------+----------------------------------------+-------------+ +--------+---------------------------------------------+------------+
| Number | Description | Status | | Number | Description | Status |
+------------+----------------------------------------+-------------+ +--------+---------------------------------------------+------------+
| 14 | 2048-bit MODP Group | MUST | | 14 | 2048-bit MODP Group | MUST |
| 19 | 256-bit random ECP group | SHOULD | | 19 | 256-bit random ECP group | SHOULD |
| 5 | 1536-bit MODP Group | SHOULD NOT | | 5 | 1536-bit MODP Group | SHOULD NOT |
| 2 | 1024-bit MODP Group | SHOULD NOT | | 2 | 1024-bit MODP Group | SHOULD NOT |
| 1 | 768-bit MODP Group | MUST NOT | | 1 | 768-bit MODP Group | MUST NOT |
| 22 | 1024-bit MODP Group with 160-bit Prime | SHOULD NOT | | 22 | 1024-bit MODP Group with 160-bit Prime | SHOULD NOT |
| | Order Subgroup | | | | Order Subgroup | |
| 23 | 2048-bit MODP Group with 224-bit Prime | SHOULD NOT | | 23 | 2048-bit MODP Group with 224-bit Prime | SHOULD NOT |
| | Order Subgroup | | | | Order Subgroup | |
| 24 | 2048-bit MODP Group with 256-bit Prime | SHOULD NOT | | 24 | 2048-bit MODP Group with 256-bit Prime | SHOULD NOT |
| | Order Subgroup | | | | Order Subgroup | |
+------------+----------------------------------------+-------------+ +--------+---------------------------------------------+------------+
Table 5
Group 14 or 2048-bit MODP Group is raised from SHOULD+ in RFC4307 as Group 14 or 2048-bit MODP Group is raised from SHOULD+ in RFC4307 as
a replacement for 1024-bit MODP Group. Group 14 is widely a replacement for 1024-bit MODP Group. Group 14 is widely
implemented and considered secure. implemented and considered secure.
Group 19 or 256-bit random ECP group was not specified in RFC4307, as Group 19 or 256-bit random ECP group was not specified in RFC4307, as
this group were not specified at that time. Group 19 is widely this group were not specified at that time. Group 19 is widely
implemented and considered secure. implemented and considered secure.
Group 5 or 1536-bit MODP Group has been downgraded from MAY in Group 5 or 1536-bit MODP Group has been downgraded from MAY in
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| Number | Description | Status | | Number | Description | Status |
+--------+---------------------------------------+------------+ +--------+---------------------------------------+------------+
| 1 | RSA Digital Signature | MUST | | 1 | RSA Digital Signature | MUST |
| 2 | Shared Key Message Integrity Code | MUST | | 2 | Shared Key Message Integrity Code | MUST |
| 3 | DSS Digital Signature | SHOULD NOT | | 3 | DSS Digital Signature | SHOULD NOT |
| 9 | ECDSA with SHA-256 on the P-256 curve | SHOULD | | 9 | ECDSA with SHA-256 on the P-256 curve | SHOULD |
| 10 | ECDSA with SHA-384 on the P-384 curve | SHOULD | | 10 | ECDSA with SHA-384 on the P-384 curve | SHOULD |
| 11 | ECDSA with SHA-512 on the P-521 curve | SHOULD | | 11 | ECDSA with SHA-512 on the P-521 curve | SHOULD |
| 14 | Digital Signature | SHOULD | | 14 | Digital Signature | SHOULD |
+--------+---------------------------------------+------------+ +--------+---------------------------------------+------------+
Table 6
RSA Digital Signature is widely deployed and therefore kept for RSA Digital Signature is widely deployed and therefore kept for
interoperability. It is expected to be downgraded in the future as interoperability. It is expected to be downgraded in the future as
its signatures are based on the older RSASSA-PKCS1-v1.5 which is no its signatures are based on the older RSASSA-PKCS1-v1.5 which is no
longer recommended. RSA authentication, as well as other specific longer recommended. RSA authentication, as well as other specific
Authentication Methods, are expected to be replaced with the generic Authentication Methods, are expected to be replaced with the generic
Digital Signature method of [RFC7427]. RSA Digital Signature is not Digital Signature method of [RFC7427]. RSA Digital Signature is not
recommended for keys smaller then 2048, but since these signatures recommended for keys smaller then 2048, but since these signatures
only have value in real-time, and need no future protection, smaller only have value in real-time, and need no future protection, smaller
keys was kept at SHOULD NOT instead of MUST NOT. keys was kept at SHOULD NOT instead of MUST NOT.
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+-------------------------------------------+------------+ +-------------------------------------------+------------+
| Description | Status | | Description | Status |
+-------------------------------------------+------------+ +-------------------------------------------+------------+
| RSA with key length 2048 | MUST | | RSA with key length 2048 | MUST |
| RSA with key length 3072 and 4096 | SHOULD | | RSA with key length 3072 and 4096 | SHOULD |
| RSA with key length between 2049 and 4095 | MAY | | RSA with key length between 2049 and 4095 | MAY |
| RSA with key length smaller than 2048 | SHOULD NOT | | RSA with key length smaller than 2048 | SHOULD NOT |
+-------------------------------------------+------------+ +-------------------------------------------+------------+
Table 7
The IKEv2 RFC7296 mandates support for the RSA keys of size 1024 or The IKEv2 RFC7296 mandates support for the RSA keys of size 1024 or
2048 bits, but here we make key sizes less than 2048 SHOULD NOT as 2048 bits, but here we make key sizes less than 2048 SHOULD NOT as
there is industry-wide trend to deprecate key lengths less than 2048 there is industry-wide trend to deprecate key lengths less than 2048
bits. bits.
4.2. Digital Signature Recommendations 4.2. Digital Signature Recommendations
Recommendations for when a hash function is involved in a signature: When Digital Signature authentication method is implemented, then the
following recommendations are applied for hash functions:
+--------+-------------+------------+---------+ +--------+-------------+------------+---------+
| Number | Description | Status | Comment | | Number | Description | Status | Comment |
+--------+-------------+------------+---------+ +--------+-------------+------------+---------+
| 1 | SHA1 | SHOULD NOT | | | 1 | SHA1 | SHOULD NOT | |
| 2 | SHA2-256 | MUST | | | 2 | SHA2-256 | MUST | |
| 3 | SHA2-384 | MAY | | | 3 | SHA2-384 | MAY | |
| 4 | SHA2-512 | SHOULD | | | 4 | SHA2-512 | SHOULD | |
+--------+-------------+------------+---------+ +--------+-------------+------------+---------+
Table 8 When Digital Signature authentication method is used with RSA
signature algorithm, then RSASSA-PSS MUST be supported and RSASSA-
With the use of Digital Signature, RSASSA-PKCS1-v1.5 MAY be PKCS1-v1.5 MAY be supported.
implemented. RSASSA-PSS MUST be implemented.
Recommendation of Authentication Method described in [RFC7427] The following table lists recommendations for authentication methods
notation: in RFC7427 [RFC7427] notation. These recommendations are applied
only if Digital Signature authentication method is implemented.
+------------------------------------+------------+---------+ +------------------------------------+------------+---------+
| Description | Status | Comment | | Description | Status | Comment |
+------------------------------------+------------+---------+ +------------------------------------+------------+---------+
| RSASSA-PSS with SHA-256 | SHOULD | | | RSASSA-PSS with SHA-256 | MUST | |
| ecdsa-with-sha256 | SHOULD | | | ecdsa-with-sha256 | SHOULD | |
| sha1WithRSAEncryption | SHOULD NOT | | | sha1WithRSAEncryption | SHOULD NOT | |
| dsa-with-sha1 | SHOULD NOT | | | dsa-with-sha1 | SHOULD NOT | |
| ecdsa-with-sha1 | SHOULD NOT | | | ecdsa-with-sha1 | SHOULD NOT | |
| RSASSA-PSS with Empty Parameters | SHOULD NOT | | | RSASSA-PSS with Empty Parameters | SHOULD NOT | |
| RSASSA-PSS with Default Parameters | SHOULD NOT | | | RSASSA-PSS with Default Parameters | SHOULD NOT | |
+------------------------------------+------------+---------+ +------------------------------------+------------+---------+
Table 9
5. Algorithms for Internet of Things 5. Algorithms for Internet of Things
Some algorithms in this document are marked for use with the Internet Some algorithms in this document are marked for use with the Internet
of Things (IoT). There are several reasons why IoT devices prefer a of Things (IoT). There are several reasons why IoT devices prefer a
different set of algorithms from regular IKEv2 clients. IoT devices different set of algorithms from regular IKEv2 clients. IoT devices
are usually very constrained, meaning the memory size and CPU power are usually very constrained, meaning the memory size and CPU power
is so limited, that these clients only have resources to implement is so limited, that these clients only have resources to implement
and run one set of algorithms. For example, instead of implementing and run one set of algorithms. For example, instead of implementing
AES and SHA, these devices typically use AES_XCBC as integrity AES and SHA, these devices typically use AES_XCBC as integrity
algorithm so SHA does not need to be implemented. algorithm so SHA does not need to be implemented.
skipping to change at page 14, line 20 skipping to change at page 14, line 10
the original text has been copied verbatim. the original text has been copied verbatim.
We would like to thank Paul Hoffman, Yaron Sheffer, John Mattsson and We would like to thank Paul Hoffman, Yaron Sheffer, John Mattsson and
Tommy Pauly for their valuable feedback. Tommy Pauly for their valuable feedback.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119,
RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode [RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
(GCM) in IPsec Encapsulating Security Payload (ESP)", RFC (GCM) in IPsec Encapsulating Security Payload (ESP)",
4106, DOI 10.17487/RFC4106, June 2005, RFC 4106, DOI 10.17487/RFC4106, June 2005,
<http://www.rfc-editor.org/info/rfc4106>. <http://www.rfc-editor.org/info/rfc4106>.
[RFC4307] Schiller, J., "Cryptographic Algorithms for Use in the [RFC4307] Schiller, J., "Cryptographic Algorithms for Use in the
Internet Key Exchange Version 2 (IKEv2)", RFC 4307, DOI Internet Key Exchange Version 2 (IKEv2)", RFC 4307,
10.17487/RFC4307, December 2005, DOI 10.17487/RFC4307, December 2005,
<http://www.rfc-editor.org/info/rfc4307>. <http://www.rfc-editor.org/info/rfc4307>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2 Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <http://www.rfc-editor.org/info/rfc7296>. 2014, <http://www.rfc-editor.org/info/rfc7296>.
[RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption [RFC5282] Black, D. and D. McGrew, "Using Authenticated Encryption
Algorithms with the Encrypted Payload of the Internet Key Algorithms with the Encrypted Payload of the Internet Key
Exchange version 2 (IKEv2) Protocol", RFC 5282, DOI Exchange version 2 (IKEv2) Protocol", RFC 5282,
10.17487/RFC5282, August 2008, DOI 10.17487/RFC5282, August 2008,
<http://www.rfc-editor.org/info/rfc5282>. <http://www.rfc-editor.org/info/rfc5282>.
9.2. Informative References 9.2. Informative References
[RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in [RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in
the Internet Key Exchange Version 2 (IKEv2)", RFC 7427, the Internet Key Exchange Version 2 (IKEv2)", RFC 7427,
DOI 10.17487/RFC7427, January 2015, DOI 10.17487/RFC7427, January 2015,
<http://www.rfc-editor.org/info/rfc7427>. <http://www.rfc-editor.org/info/rfc7427>.
[RFC6989] Sheffer, Y. and S. Fluhrer, "Additional Diffie-Hellman [RFC6989] Sheffer, Y. and S. Fluhrer, "Additional Diffie-Hellman
Tests for the Internet Key Exchange Protocol Version 2 Tests for the Internet Key Exchange Protocol Version 2
(IKEv2)", RFC 6989, DOI 10.17487/RFC6989, July 2013, (IKEv2)", RFC 6989, DOI 10.17487/RFC6989, July 2013,
<http://www.rfc-editor.org/info/rfc6989>. <http://www.rfc-editor.org/info/rfc6989>.
[RFC7815] Kivinen, T., "Minimal Internet Key Exchange Version 2 [RFC7815] Kivinen, T., "Minimal Internet Key Exchange Version 2
(IKEv2) Initiator Implementation", RFC 7815, DOI 10.17487/ (IKEv2) Initiator Implementation", RFC 7815,
RFC7815, March 2016, DOI 10.17487/RFC7815, March 2016,
<http://www.rfc-editor.org/info/rfc7815>. <http://www.rfc-editor.org/info/rfc7815>.
[IKEV2-IANA] [IKEV2-IANA]
, "Internet Key Exchange Version 2 (IKEv2) Parameters", , "Internet Key Exchange Version 2 (IKEv2) Parameters",
<http://www.iana.org/assignments/ikev2-parameters>. <http://www.iana.org/assignments/ikev2-parameters>.
[TRANSCRIPTION] [TRANSCRIPTION]
Bhargavan, K. and G. Leurent, "Transcript Collision Bhargavan, K. and G. Leurent, "Transcript Collision
Attacks: Breaking Authentication in TLS, IKE, and SSH", Attacks: Breaking Authentication in TLS, IKE, and SSH",
NDSS , feb 2016. NDSS , feb 2016.
[IEEE-802-15-4] [IEEE-802-15-4]
, "IEEE Standard for Low-Rate Wireless Personal Area "IEEE Standard for Low-Rate Wireless Personal Area
Networks (WPANs)", IEEE Standard 802.15.4, 2015. Networks (WPANs)", IEEE Standard 802.15.4, 2015.
[IEEE-802-15-9] [IEEE-802-15-9]
, "IEEE Recommended Practice for Transport of Key "IEEE Recommended Practice for Transport of Key Management
Management Protocol (KMP) Datagrams", IEEE Standard Protocol (KMP) Datagrams", IEEE Standard 802.15.9, 2016.
802.15.9, 2016.
Authors' Addresses Authors' Addresses
Yoav Nir Yoav Nir
Check Point Software Technologies Ltd. Check Point Software Technologies Ltd.
5 Hasolelim st. 5 Hasolelim st.
Tel Aviv 6789735 Tel Aviv 6789735
Israel Israel
EMail: ynir.ietf@gmail.com EMail: ynir.ietf@gmail.com
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