--- 1/draft-ietf-drip-arch-18.txt 2022-01-15 20:13:11.029834216 -0800 +++ 2/draft-ietf-drip-arch-19.txt 2022-01-15 20:13:11.081835524 -0800 @@ -1,24 +1,24 @@ drip S. Card Internet-Draft A. Wiethuechter Intended status: Informational AX Enterprize -Expires: 17 June 2022 R. Moskowitz +Expires: 20 July 2022 R. Moskowitz HTT Consulting S. Zhao (Editor) Tencent A. Gurtov Linköping University - 14 December 2021 + 16 January 2022 Drone Remote Identification Protocol (DRIP) Architecture - draft-ietf-drip-arch-18 + draft-ietf-drip-arch-19 Abstract This document describes an architecture for protocols and services to support Unmanned Aircraft System Remote Identification and tracking (UAS RID), plus RID-related communications. This architecture adheres to the requirements listed in the DRIP Requirements document. Status of This Memo @@ -28,84 +28,84 @@ 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 https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on 17 June 2022. + This Internet-Draft will expire on 20 July 2022. Copyright Notice - Copyright (c) 2021 IETF Trust and the persons identified as the + Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components - extracted from this document must include Simplified BSD License text - as described in Section 4.e of the Trust Legal Provisions and are - provided without warranty as described in the Simplified BSD License. + extracted from this document must include Revised BSD License text as + described in Section 4.e of the Trust Legal Provisions and are + provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Overview of Unmanned Aircraft System (UAS) Remote ID (RID) and Standardization . . . . . . . . . . . . . . . . . . . 3 1.2. Overview of Types of UAS Remote ID . . . . . . . . . . . 4 1.2.1. Broadcast RID . . . . . . . . . . . . . . . . . . . . 4 1.2.2. Network RID . . . . . . . . . . . . . . . . . . . . . 5 1.3. Overview of USS Interoperability . . . . . . . . . . . . 7 1.4. Overview of DRIP Architecture . . . . . . . . . . . . . . 8 - 2. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 10 - 2.1. Architecture Terminology . . . . . . . . . . . . . . . . 10 - 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 10 - 2.3. Claims, Assertions, Attestations, and Certificates . . . 10 - 2.4. Additional Definitions . . . . . . . . . . . . . . . . . 11 - 3. HHIT as the DRIP Entity Identifier . . . . . . . . . . . . . 11 - 3.1. UAS Remote Identifiers Problem Space . . . . . . . . . . 12 - 3.2. HHIT as A Trustworthy DRIP Entity Identifier . . . . . . 12 - 3.3. HHIT for DRIP Identifier Registration and Lookup . . . . 14 - 3.4. HHIT as a Cryptographic Identifier . . . . . . . . . . . 14 - 4. DRIP Identifier Registration and Registries . . . . . . . . . 14 - 4.1. Public Information Registry . . . . . . . . . . . . . . . 15 - 4.1.1. Background . . . . . . . . . . . . . . . . . . . . . 15 - 4.1.2. DNS as the Public DRIP Identifier Registry . . . . . 15 - 4.2. Private Information Registry . . . . . . . . . . . . . . 15 - 4.2.1. Background . . . . . . . . . . . . . . . . . . . . . 15 - 4.2.2. EPP and RDAP as the Private DRIP Identifier - Registry . . . . . . . . . . . . . . . . . . . . . . 16 - 4.2.3. Alternative Private DRIP Registry methods . . . . . . 16 - 5. DRIP Identifier Trust . . . . . . . . . . . . . . . . . . . . 16 - 6. Harvesting Broadcast Remote ID messages for UTM Inclusion . . 17 - 6.1. The CS-RID Finder . . . . . . . . . . . . . . . . . . . . 18 - 6.2. The CS-RID SDSP . . . . . . . . . . . . . . . . . . . . . 18 - 7. DRIP Contact . . . . . . . . . . . . . . . . . . . . . . . . 18 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 - 10. Privacy & Transparency Considerations . . . . . . . . . . . . 19 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 20 - 11.2. Informative References . . . . . . . . . . . . . . . . . 20 + 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 9 + 3. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 9 + 3.1. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 9 + 3.2. Claims, Assertions, Attestations, and Certificates . . . 10 + 3.3. Additional Definitions . . . . . . . . . . . . . . . . . 10 + 4. HHIT as the DRIP Entity Identifier . . . . . . . . . . . . . 10 + 4.1. UAS Remote Identifiers Problem Space . . . . . . . . . . 11 + 4.2. HHIT as A Trustworthy DRIP Entity Identifier . . . . . . 11 + 4.3. HHIT for DRIP Identifier Registration and Lookup . . . . 13 + 4.4. HHIT as a Cryptographic Identifier . . . . . . . . . . . 13 + 5. DRIP Identifier Registration and Registries . . . . . . . . . 13 + 5.1. Public Information Registry . . . . . . . . . . . . . . . 14 + 5.1.1. Background . . . . . . . . . . . . . . . . . . . . . 14 + 5.1.2. DNS as the Public DRIP Identifier Registry . . . . . 14 + 5.2. Private Information Registry . . . . . . . . . . . . . . 14 + 5.2.1. Background . . . . . . . . . . . . . . . . . . . . . 14 + 5.2.2. EPP and RDAP as the Private DRIP Identifier + Registry . . . . . . . . . . . . . . . . . . . . . . 15 + 5.2.3. Alternative Private DRIP Registry methods . . . . . . 15 + 6. DRIP Identifier Trust . . . . . . . . . . . . . . . . . . . . 15 + 7. Harvesting Broadcast Remote ID messages for UTM Inclusion . . 16 + 7.1. The CS-RID Finder . . . . . . . . . . . . . . . . . . . . 17 + 7.2. The CS-RID SDSP . . . . . . . . . . . . . . . . . . . . . 17 + 8. DRIP Contact . . . . . . . . . . . . . . . . . . . . . . . . 17 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 18 + 11. Privacy & Transparency Considerations . . . . . . . . . . . . 18 + 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 12.1. Normative References . . . . . . . . . . . . . . . . . . 19 + 12.2. Informative References . . . . . . . . . . . . . . . . . 19 Appendix A. Overview of Unmanned Aircraft Systems (UAS) Traffic - Management (UTM) . . . . . . . . . . . . . . . . . . . . 23 - A.1. Operation Concept . . . . . . . . . . . . . . . . . . . . 23 - A.2. UAS Service Supplier (USS) . . . . . . . . . . . . . . . 24 - A.3. UTM Use Cases for UAS Operations . . . . . . . . . . . . 24 + Management (UTM) . . . . . . . . . . . . . . . . . . . . 22 + A.1. Operation Concept . . . . . . . . . . . . . . . . . . . . 22 + A.2. UAS Service Supplier (USS) . . . . . . . . . . . . . . . 23 + A.3. UTM Use Cases for UAS Operations . . . . . . . . . . . . 23 Appendix B. Automatic Dependent Surveillance Broadcast - (ADS-B) . . . . . . . . . . . . . . . . . . . . . . . . . 25 - Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 25 + (ADS-B) . . . . . . . . . . . . . . . . . . . . . . . . . 24 + Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 1. Introduction This document describes an architecture for protocols and services to support Unmanned Aircraft System Remote Identification and tracking (UAS RID), plus RID-related communications. The architecture takes into account both current (including proposed) regulations and non- IETF technical standards. @@ -163,21 +163,21 @@ With release 16, the 3GPP completed the UAS RID requirement study [TS-22.825] and proposed a set of use cases in the mobile network and the services that can be offered based on RID. Release 17 specification focuses on enhanced UAS service requirements and provides the protocol and application architecture support that will be applicable for both 4G and 5G networks. The study of Further Architecture Enhancement for Uncrewed Aerial Vehicles (UAV) and Urban Air Mobility (UAM) [FS_AEUA] in release 18 further enhances the communication mechanism between UAS and USS/UTM. The - RID discussed in Section 3 may be used as the 3GPP CAA-level ID + RID discussed in Section 4 may be used as the 3GPP CAA-level ID for Remote Identification purposes. 1.2. Overview of Types of UAS Remote ID 1.2.1. Broadcast RID [F3411] defines a set of RID messages for direct, one-way, broadcast transmissions from the UA over Bluetooth or Wi-Fi. These are currently defined as MAC-Layer messages. Internet (or other Wide Area Network) connectivity is only needed for UAS registry @@ -202,31 +202,31 @@ | Observer's device (e.g., smartphone) | +--------------------------------------+ Figure 1 Broadcast RID provides information only about unmanned aircraft (UA) within direct RF LOS, typically similar to visual Light-Of-Sight (LOS), with a range up to approximately 1 km. This information may be 'harvested' from received broadcasts and made available via the Internet, enabling surveillance of areas too large for local direct - visual observation or direct RF link based ID (see Section 6). + visual observation or direct RF link based ID (see Section 7). 1.2.2. Network RID [F3411], using the same data dictionary that is the basis of Broadcast RID messages, defines a Network Remote Identification (Net- RID) data flow as follows. * The information to be reported via RID is generated by the UAS - (typically some by the UA and some by the GCS, e.g. their - respective GNSS derived locations). + (typically some by the UA and some by the GCS (Ground Control + Station), e.g. their respective GNSS derived locations). * The information is sent by the UAS (UA or GCS) via unspecified means to the cognizant Network Remote Identification Service Provider (Net-RID SP), typically the USS under which the UAS is operating if participating in UTM. * The Net-RID SP publishes via the Discovery and Synchronization Service (DSS) over the Internet that it has operations in various 4-D airspace volumes, describing the volumes but not the operations. @@ -246,76 +246,75 @@ The minimum Net-RID data flow is illustrated in Figure 2: +-------------+ ****************** | UA | * Internet * +--o-------o--+ * * | | * * | | * * +------------+ | '--------*--(+)-----------*-----o | | * | * | | - | .--------*--(+)-----------*-----o NET-RID SP | + | .--------*--(+)-----------*-----o Net-RID SP | | | * * | | | | * .------*-----o | | | * | * +------------+ | | * | * | | * | * +------------+ | | * '------*-----o | - | | * * | NET-RID DP | + | | * * | Net-RID DP | | | * .------*-----o | | | * | * +------------+ | | * | * | | * | * +------------+ +--o-------o--+ * '------*-----o Observer's | | GCS | * * | Device | +-------------+ ****************** +------------+ Figure 2 Command and Control (C2) must flow from the GCS to the UA via some path, currently (in the year of 2021) typically a direct RF link, but - with increasing beyond Visual Line of Sight (BVLOS) operations + with increasing beyond Visual Line of Sight (BVLOS) operations, it is expected often to be wireless links at either end with the Internet between. Telemetry (at least UA's position and heading) flows from the UA to the GCS via some path, typically the reverse of the C2 path. Thus, RID information pertaining to both the GCS and the UA can be sent, by whichever has Internet connectivity, to the Net-RID SP, typically the USS managing the UAS operation. The Net-RID SP forwards RID information via the Internet to subscribed Net-RID DP, typically USS. Subscribed Net-RID DP forward RID information via the Internet to subscribed Observer devices. Regulations require and [F3411] describes RID data elements that must be transported end-to-end from the UAS to the subscribed Observer devices. [F3411] prescribes the protocols between the Net-RID SP, Net-RID DP, - and the Discovery and Synchronization Service (DSS). It also - prescribes data elements (in JSON) between Observer and Net-RID DP. - DRIP could address standardization of secure protocols between the UA - and GCS (over direct wireless and Internet connection), between the - UAS and the Net-RID SP, and/or between the Net-RID DP and Observer - devices. + and the DSS. It also prescribes data elements (in JSON) between + Observer and Net-RID DP. DRIP could address standardization of + secure protocols between the UA and GCS (over direct wireless and + Internet connection), between the UAS and the Net-RID SP, and/or + between the Net-RID DP and Observer devices. Informative note: Neither link layer protocols nor the use of links (e.g., the link often existing between the GCS and the UA) for any purpose other than carriage of RID information is in the scope of [F3411] Network RID. 1.3. Overview of USS Interoperability With Net-RID, there is direct communication between each UAS and its - USS. Multiple USS exchange information with the assistance of a - Discovery and Synchronization Service (DSS) so all USS collectively - have knowledge about all activities in a 4D airspace. + USS. Multiple USS exchange information with the assistance of a DSS + so all USS collectively have knowledge about all activities in a 4D + airspace. The interactions among an Observer, multiple UAS, and their USS are shown in Figure 3. +------+ +----------+ +------+ | UAS1 | | Observer | | UAS2 | +----o-+ +-----o----+ +-o----+ | | | | | | ******|*************|************|****** @@ -381,63 +379,63 @@ UAS RID and closely related needs. DRIP will specify how to apply IETF standards, complementing [F3411] and other external standards, to satisfy UAS RID requirements. This document outlines the DRIP architecture in the context of the UAS RID architecture. This includes presenting the gaps between the CAAs' Concepts of Operations and [F3411] as it relates to the use of Internet technologies and UA direct RF communications. Issues include, but are not limited to: - o Design of trustworthy remote identifiers (Section 3). + - Design of trustworthy remote identifiers (Section 4). - Mechanisms to leverage Domain Name System (DNS [RFC1034]), Extensible Provisioning Protocol (EPP [RFC5731]) and - Registration Data Access Protocol (RDAP) ([RFC7482]) for - publishing public and private information (see Section 4.1 and - Section 4.2). + Registration Data Access Protocol (RDAP) ([RFC9082]) for + publishing public and private information (see Section 5.1 and + Section 5.2). - Specific authentication methods and message payload formats to enable verification that Broadcast RID messages were sent by - the claimed sender (Section 5) and that sender is in the - claimed registry (Section 4 and Section 5). + the claimed sender (Section 6) and that sender is in the + claimed registry (Section 5 and Section 6). - Harvesting broadcast RID messages for UTM inclusion - (Section 6). + (Section 7). - Methods for instantly establishing secure communications between an Observer and the pilot of an observed UAS - (Section 7). - - - Privacy in RID messages (PII protection) (Section 10). + (Section 8). -2. Terms and Definitions + - Privacy in RID messages (PII protection) (Section 11). -2.1. Architecture Terminology +2. Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all - capitals, as shown above. + capitals, as shown here. -2.2. Abbreviations +3. Terms and Definitions + +3.1. Abbreviations EdDSA: Edwards-Curve Digital Signature Algorithm HHIT: Hierarchical HIT HIP: Host Identity Protocol HIT: Host Identity Tag -2.3. Claims, Assertions, Attestations, and Certificates +3.2. Claims, Assertions, Attestations, and Certificates This section introduces the terms "Claims", "Assertions", "Attestations", and "Certificates" as used in DRIP. DRIP certificate has a different context compared with security certificates and Public Key Infrastructure used in X.509. Claims: A claim in DRIP is a predicate (e.g., "X is Y", "X has property Y", and most importantly "X owns Y" or "X is owned by Y"). @@ -455,274 +453,275 @@ relationship with another entity, along with other information, and the asserting entity signs the assertion, thereby making it an attestation. Certificates: A certificate in DRIP is an attestation, strictly over identity information, signed by a third party. This third party should be one with no stake in the attestation(s) its signing over. -2.4. Additional Definitions +3.3. Additional Definitions This document uses terms defined in [I-D.ietf-drip-reqs]. -3. HHIT as the DRIP Entity Identifier +4. HHIT as the DRIP Entity Identifier This section describes the DRIP architectural approach to meeting the basic requirements of a DRIP entity identifier within external technical standard ASTM [F3411] and regulatory constraints. It justifies and explains the use of Hierarchical Host Identity Tags (HHITs) as self-asserting IPv6 addresses suitable as a UAS ID type and more generally as trustworthy multipurpose remote identifiers. - Self-asserting in this usage is given the Host Identity (HI), the + Self-asserting in this usage is given by the Host Identity (HI), the HHIT ORCHID construction and a signature of the HHIT by the HI can both be validated. The explicit registration hierarchy within the HHIT provides registry discovery (managed by a Registrar) to either yield the HI for 3rd-party (who is looking for ID attestation) validation or prove the HHIT and HI have uniquely been registered. -3.1. UAS Remote Identifiers Problem Space +4.1. UAS Remote Identifiers Problem Space A DRIP entity identifier needs to be "Trustworthy" (See DRIP Requirement GEN-1, ID-4 and ID-5 in [I-D.ietf-drip-reqs]). This means that given a sufficient collection of RID messages, an Observer can establish that the identifier claimed therein uniquely belongs to - the claimant: that the only way for any other entity to prove - ownership of that identifier would be to obtain information that - ought to be available only to the legitimate owner of the identifier - (e.g., a cryptographic private key). - - To satisfy DRIP requirements and maintain important security - properties, the DRIP identifier should be self-generated by the - entity it names (e.g., a UAS) and registered (e.g., with a USS, see - Requirements GEN-3 and ID-2). + the claimant. To satisfy DRIP requirements and maintain important + security properties, the DRIP identifier should be self-generated by + the entity it names (e.g., a UAS) and registered (e.g., with a USS, + see Requirements GEN-3 and ID-2). Broadcast RID, especially its support for Bluetooth 4, imposes severe constraints. ASTM RID [F3411] allows a UAS ID of types 1, 2 and 3 of 20 bytes; a revision to [F3411], currently in balloting (as of Oct 2021), adds type 4, Session IDs, to be standardized by IETF and other standard development organizations (SDOs) as extensions to ASTM RID, consumes one of those bytes to index the sub-type, leaving only 19 - for the identifier (see DRIP Requirement ID-1). Likewise, the - maximum ASTM RID [F3411] Authentication Message payload is 201 bytes - for most authentication types, but for type 5, also added in this - revision, for IETF and other SDOs to develop Specific Authentication - Methods as extensions to ASTM RID, one byte is consumed to index the - sub-type, leaving only 200 for DRIP authentication payloads, - including one or more DRIP entity identifiers and associated - authentication data. + for the identifier (see DRIP Requirement ID-1). -3.2. HHIT as A Trustworthy DRIP Entity Identifier + Likewise, the maximum ASTM RID [F3411] Authentication Message payload + is 201 bytes for most authentication types, but for type 5, also + added in this revision, for IETF and other SDOs to develop Specific + Authentication Methods as extensions to ASTM RID, one byte is + consumed to index the sub-type, leaving only 200 for DRIP + authentication payloads, including one or more DRIP entity + identifiers and associated authentication data. + +4.2. HHIT as A Trustworthy DRIP Entity Identifier A Remote ID that can be trustworthily used in the RID Broadcast mode - can be built from an asymmetric keypair. Rather than using a key - signing operation to claim ownership of an ID that does not guarantee - name uniqueness, in this method the ID is cryptographically derived - directly from the public key. The proof of ID ownership (verifiable - attestation, versus mere claim) is guaranteed by signing this - cryptographic ID with the associated private key. The association - between the ID and the private key is ensured by cryptographically - binding the public key with the ID, more specifically the ID results - from the hash of the public key. It is statistically hard for - another entity to create a public key that would generate (spoof) the - ID. + can be built from an asymmetric keypair. In this method the ID is + cryptographically derived directly from the public key. The proof of + ID ownership (verifiable attestation, versus mere claim) is + guaranteed by signing this cryptographic ID with the associated + private key. The association between the ID and the private key is + ensured by cryptographically binding the public key with the ID, more + specifically the ID results from the hash of the public key. The + public key is designated as the HI while the ID is designated as the + HIT. - The basic HIT is designed statistically unique through the + By construction, the HIT is statistically unique through the cryptographic hash feature of second-preimage resistance. The cryptographically-bound addition of the Hierarchy and an HHIT - registration process (e.g. based on Extensible Provisioning Protocol, - [RFC5730]) provide complete, global HHIT uniqueness. This + registration process provide complete, global HHIT uniqueness. This registration forces the attacker to generate the same public key rather than a public key that generates the same HHIT. This is in contrast to general IDs (e.g. a UUID or device serial number) as the subject in an X.509 certificate. - A DRIP identifier can be assigned to a UAS as a static HHIT by its - manufacturer, such as a single HI and derived HHIT encoded as a - hardware serial number per [CTA2063A]. Such a static HHIT SHOULD - only be used to bind one-time use DRIP identifiers to the unique UA. - Depending upon implementation, this may leave a HI private key in the - possession of the manufacturer (more details in Section 9). - A UA equipped for Broadcast RID SHOULD be provisioned not only with its HHIT but also with the HI public key from which the HHIT was derived and the corresponding private key, to enable message signature. A UAS equipped for Network RID SHOULD be provisioned likewise; the private key resides only in the ultimate source of Network RID messages (i.e. on the UA itself if the GCS is merely relaying rather than sourcing Network RID messages). Each Observer device SHOULD be provisioned either with public keys of the DRIP identifier root registries or certificates for subordinate registries. HHITs can also be used throughout the USS/UTM system. The Operators, Private Information Registries, as well as other UTM entities, can use HHITs for their IDs. Such HHITs can facilitate DRIP security functions such as used with HIP to strongly mutually authenticate and encrypt communications. A self-attestation of a HHIT used as a UAS ID can be done in as - little as 84 bytes, by avoiding an explicit encoding technology like - ASN.1 or Concise Binary Object Representation (CBOR [RFC8949]). This - attestation consists of only the HHIT, a timestamp, and the EdDSA - signature on them. + little as 84 bytes when Ed25519 [RFC8032] is used, by avoiding an + explicit encoding technology like ASN.1 or Concise Binary Object + Representation (CBOR [RFC8949]). This attestation consists of only + the HHIT, a timestamp, and the EdDSA signature on them. + + A DRIP identifier can be assigned to a UAS as a static HHIT by its + manufacturer, such as a single HI and derived HHIT encoded as a + hardware serial number per [CTA2063A]. Such a static HHIT SHOULD + only be used to bind one-time use DRIP identifiers to the unique UA. + Depending upon implementation, this may leave a HI private key in the + possession of the manufacturer (more details in Section 10). In general, Internet access may be needed to validate Attestations or Certificates. This may be obviated in the most common cases (e.g. attestation of the UAS ID), even in disconnected environments, by prepopulating small caches on Observer devices with Registry public keys and a chain of Attestations or Certificates (tracing a path through the Registry tree). This is assuming all parties on the trust path also use HHITs for their identities. -3.3. HHIT for DRIP Identifier Registration and Lookup +4.3. HHIT for DRIP Identifier Registration and Lookup - Remote ID needs a deterministic lookup mechanism that rapidly - provides actionable information about the identified UA. Given the - size constraints imposed by the Bluetooth 4 broadcast media, the UAS - ID itself needs to be a non-spoofable inquiry input into the lookup. + RID needs a deterministic lookup mechanism that rapidly provides + actionable information about the identified UA. Given the size + constraints imposed by the Bluetooth 4 broadcast media, the UAS ID + itself needs to be a non-spoofable inquiry input into the lookup. A DRIP registration process based on the explicit hierarchy within a HHIT provides manageable uniqueness of the HI for the HHIT. This is the defense against a cryptographic hash second pre-image attack on the HHIT (e.g. multiple HIs yielding the same HHIT, see Requirement ID-3). A lookup of the HHIT into this registration data provides the - registered HI for HHIT proof. A first-come-first-serve registration - for a HHIT provides deterministic access to any other needed - actionable information based on inquiry access authority (more - details in Section 4.2). + registered HI for HHIT proof of ownership. A first-come-first-serve + registration for a HHIT provides deterministic access to any other + needed actionable information based on inquiry access authority (more + details in Section 5.2). -3.4. HHIT as a Cryptographic Identifier +4.4. HHIT as a Cryptographic Identifier The only (known to the authors at the time of this writing) extant types of IP address compatible identifiers cryptographically derived from the public keys of the identified entities are Cryptographically Generated Addresses (CGAs) [RFC3972] and Host Identity Tags (HITs) [RFC7401]. CGAs and HITs lack registration/retrieval capability. To provide this, each HHIT embeds plaintext information designating the - hierarchy within which is registered and a cryptographic hash of that - information concatenated with the entity's public key, etc. Although - hash collisions may occur, the registrar can detect them and reject - registration requests rather than issue credentials, e.g., by + hierarchy within which it is registered and a cryptographic hash of + that information concatenated with the entity's public key, etc. + Although hash collisions may occur, the registrar can detect them and + reject registration requests rather than issue credentials, e.g., by enforcing a first-claimed, first-attested policy. Pre-image hash attacks are also mitigated through this registration process, locking the HHIT to a specific HI -4. DRIP Identifier Registration and Registries +5. DRIP Identifier Registration and Registries DRIP registries hold both public and private UAS information resulting from the DRIP identifier registration process. Given these different uses, and to improve scalability, security, and simplicity of administration, the public and private information can be stored in different registries. This section introduces the public and private information registries for DRIP identifiers. This DRIP Identifier registration process satisfies the following DRIP requirements defined in [I-D.ietf-drip-reqs]: GEN-3, GEN-4, ID-2, ID- 4, ID-6, PRIV-3, PRIV-4, REG-1, PRG-2, REG-3 and REG-4. -4.1. Public Information Registry +5.1. Public Information Registry -4.1.1. Background +5.1.1. Background The public registry provides trustable information such as attestations of RID ownership and registration with the HDA (Hierarchical HIT Domain Authority). Optionally, pointers to the registries for the HDA and RAA (Registered Assigning Authority)implicit in the RID can be included (e.g., for HDA and RAA HHIT|HI used in attestation signing operations). This public information will be principally used by Observers of Broadcast RID messages. Data on UAS that only use Network RID, is available via an Observer's Net-RID DP that would tend to directly provide all public registry information. The Observer may visually "see" these Net-RID UAS, but they may be silent to the Observer. The Net-RID DP is the only source of information based on a query for an airspace volume. -4.1.2. DNS as the Public DRIP Identifier Registry +5.1.2. DNS as the Public DRIP Identifier Registry A DRIP identifier SHOULD be registered as an Internet domain name (at an arbitrary level in the hierarchy, e.g. in .ip6.arpa). Thus DNS can provide all the needed public DRIP information. A standardized HHIT FQDN (Fully Qualified Domain Name) can deliver the HI via a HIP RR (Resource Record) [RFC8005] and other public information (e.g., RRA and HDA PTRs, and HIP RVS (Rendezvous Servers) [RFC8004]). These public information registries can use secure DNS transport (e.g. DNS over TLS) to deliver public information that is not inherently trustable (e.g. everything other than attestations). -4.2. Private Information Registry +5.2. Private Information Registry -4.2.1. Background +5.2.1. Background The private information required for DRIP identifiers is similar to that required for Internet domain name registration. A DRIP identifier solution can leverage existing Internet resources: registration protocols, infrastructure, and business models, by fitting into an ID structure compatible with DNS names. The HHIT hierarchy can provide the needed scalability and management structure. It is expected that the private registry function will be provided by the same organizations that run a USS, and likely integrated with a USS. The lookup function may be implemented by the Net-RID DPs. -4.2.2. EPP and RDAP as the Private DRIP Identifier Registry +5.2.2. EPP and RDAP as the Private DRIP Identifier Registry A DRIP private information registry supports essential registry operations (e.g. add, delete, update, query) using interoperable open standard protocols. It can accomplish this by using the Extensible Provisioning Protocol (EPP [RFC5730]) and the Registry Data Access - Protocol (RDAP RFC7480] [RFC7482] [RFC7483]). The DRIP private + Protocol (RDAP RFC7480] [RFC9082] [RFC9083]). The DRIP private information registry in which a given UAS is registered needs to be findable, starting from the UAS ID, using the methods specified in [RFC7484]. -4.2.3. Alternative Private DRIP Registry methods +5.2.3. Alternative Private DRIP Registry methods A DRIP private information registry might be an access controlled DNS (e.g. via DNS over TLS). Additionally, WebFinger [RFC7033] can be deployed. These alternative methods may be used by Net-RID DP with specific customers. -5. DRIP Identifier Trust +6. DRIP Identifier Trust While the DRIP entity identifier is self-asserting, it alone does not provide the "trustworthiness" specified in [I-D.ietf-drip-reqs]. For that it MUST be registered (under DRIP Registries) and be actively - used by the party (in most cases the UA). For Broadcast RID this is - a challenge to balance the original requirements of Broadcast RID and - the efforts needed to satisfy the DRIP requirements all under severe - constraints. + used by the party (in most cases the UA). For example, when a sender + simply possessing a DET (DRIP Entity Tag which is a HHIT-based UAS + ID) and broadcasting a claim that it belongs to that sender proves + nothing about that sender's identity. Even the sender using that + HI's private key to sign static data proves nothing as well, as it is + subject to trivial replay attacks. Only sending the DET and a + signature on frequently changing data that can be sanity checked by + the Observer (such as a Location/Vector message) proves that the + observed UA possesses the claimed UAS ID. - From received Broadcast RID messages and information that can be - looked up using the received UAS ID in online registries or local - caches, it is possible to establish levels of trust in the asserted - information and the Operator. + For Broadcast RID, this is a challenge to balance the original + requirements of Broadcast RID and the efforts needed to satisfy the + DRIP requirements all under severe constraints. From received + Broadcast RID messages and information that can be looked up using + the received UAS ID in online registries or local caches, it is + possible to establish levels of trust in the asserted information and + the Operator. An optimization of different DRIP Authentication Messages allows an Observer, without Internet connection (offline) or with (online), to be able to validate a UAS DRIP ID in real-time. First is the sending of Broadcast Attestations (over DRIP Link Authentication Messages) - containing the relevant registration of the UA's DRIP ID in the - claimed Registry. Next is sending DRIP Wrapper Authentication - Messages that sign over both static (e.g. above registration) and - dynamically changing data (such as UA location data). Combining - these two sets of information an Observer can piece together a chain - of trust and real-time evidence to make their determination of the - UAs claims. + [I-D.ietf-drip-auth] containing the relevant registration of the UA's + DRIP ID in the claimed Registry. Next is sending DRIP Wrapper + Authentication Messages that sign over both static (e.g. above + registration) and dynamically changing data (such as UA location + data). Combining these two sets of information an Observer can piece + together a chain of trust and real-time evidence to make their + determination of the UAs claims. This process (combining the DRIP entity identifier, Registries and Authentication Formats for Broadcast RID) can satisfy the following DRIP requirement defined in [I-D.ietf-drip-reqs]: GEN-1, GEN-2, GEN- 3, ID-2, ID-3, ID-4 and ID-5. -6. Harvesting Broadcast Remote ID messages for UTM Inclusion +7. Harvesting Broadcast Remote ID messages for UTM Inclusion ASTM anticipated that regulators would require both Broadcast RID and Network RID for large UAS, but allow RID requirements for small UAS to be satisfied with the operator's choice of either Broadcast RID or Network RID. The EASA initially specified Broadcast RID for UAS of essentially all UAS and is now also considering Network RID. The FAA RID Final Rules [FAA_RID] permit only Broadcast RID for rule compliance, but still encourage Network RID for complementary functionality, especially in support of UTM. @@ -750,55 +749,55 @@ Further, gateways with additional sensors (e.g. smartphones with cameras) can provide independent information on the UA type and size, confirming or refuting those claims made in the RID messages. This Crowd Sourced Remote ID (CS-RID) would be a significant enhancement, beyond baseline DRIP functionality; if implemented, it adds two more entity types. This approach satisfies the following DRIP requirements defined in [I-D.ietf-drip-reqs]: GEN-5, GEN-11, and REG-1. -6.1. The CS-RID Finder +7.1. The CS-RID Finder A CS-RID Finder is the gateway for Broadcast Remote ID Messages into the UTM. It performs this gateway function via a CS-RID SDSP. A CS- RID Finder could implement, integrate, or accept outputs from, a Broadcast RID receiver. However, it should not depend upon a direct interface with a GCS, Net-RID SP, Net-RID DP or Network RID client. It would present a TBD interface to a CS-RID SDSP, similar to but readily distinguishable from that between a GCS and a Net-RID SP. -6.2. The CS-RID SDSP +7.2. The CS-RID SDSP A CS-RID SDSP aggregates and processes (e.g., estimates UA location using including using multilateration when possible) information collected by CS-RID Finders. A CS-RID SDSP should appear (i.e. present the same interface) to a Net-RID SP as a Net-RID DP. -7. DRIP Contact +8. DRIP Contact One of the ways in which DRIP can enhance [F3411] with immediately actionable information is by enabling an Observer to instantly initiate secure communications with the UAS remote pilot, Pilot In Command, operator, USS under which the operation is being flown, or other entity potentially able to furnish further information regarding the operation and its intent and/or to immediately influence further conduct or termination of the operation (e.g., land or otherwise exit an airspace volume). Such potentially distracting communications demand strong "AAA" (Authentication, Attestation, Authorization, Access Control, Accounting, Attribution, Audit) per applicable policies (e.g., of the cognizant CAA). - A DRIP entity identifier based on a HHIT as outlined in Section 3 + A DRIP entity identifier based on a HHIT as outlined in Section 4 embeds an identifier of the registry in which it can be found (expected typically to be the USS under which the UAS is flying) and - the procedures outlined in Section 5 enable Observer verification of + the procedures outlined in Section 6 enable Observer verification of that relationship. A DRIP entity identifier with suitable records in public and private registries as outlined in Section 5 can enable lookup not only of information regarding the UAS but also identities of and pointers to information regarding the various associated entities (e.g., the USS under which the UAS is flying an operation), including means of contacting those associated entities (i.e., locators, typically IP addresses). An Observer equipped with HIP can initiate a Base Exchange (BEX) and establish a Bound End to End Tunnel (BEET) protected by IPsec Encapsulating Security Payload (ESP) encryption to a likewise equipped and identified entity: the UA @@ -810,81 +809,81 @@ currently usable locator (IP address); and there must be currently usable bidirectional IP (not necessarily Internet) connectivity between the parties. Given a BEET, arbitrary standard higher layer protocols can then be used for Observer to Pilot (O2P) communications (e.g., SIP [RFC3261] et seq), V2X communications (e.g., [MAVLink]), etc. This approach satisfies DRIP requirement GEN-6 Contact, supports satisfaction of requirements [I-D.ietf-drip-reqs] GEN-8, GEN-9, PRIV-2, PRIV-5 and REG-3, and is compatible with all other DRIP requirements. -8. IANA Considerations +9. IANA Considerations This document does not make any IANA request. -9. Security Considerations +10. Security Considerations The security provided by asymmetric cryptographic techniques depends upon protection of the private keys. A manufacturer that embeds a private key in an UA may have retained a copy. A manufacturer whose UA are configured by a closed source application on the GCS which communicates over the Internet with the factory may be sending a copy of a UA or GCS self-generated key back to the factory. Keys may be extracted from a GCS or UA. The RID sender of a small harmless UA (or the entire UA) could be carried by a larger dangerous UA as a "false flag." Compromise of a registry private key could do widespread harm. Key revocation procedures are as yet to be determined. These risks are in addition to those involving Operator key management practices. -10. Privacy & Transparency Considerations +11. Privacy & Transparency Considerations Broadcast RID messages can contain Personally Identifiable Information (PII). A viable architecture for PII protection would be symmetric encryption of the PII using a session key known to the UAS and its USS. Authorized Observers could obtain plaintext in either of two ways. An Observer can send the UAS ID and the cyphertext to a server that offers decryption as a service. An Observer can send the UAS ID only to a server that returns the session key, so that Observer can directly locally decrypt all cyphertext sent by that UA during that session (UAS operation). In either case, the server can - be: a Public Safety USS; the Observer's own USS; or the UA's USS if + be: a Public Safety USS, the Observer's own USS, or the UA's USS if the latter can be determined (which under DRIP it can be, from the UAS ID itself). PII can be protected unless the UAS is informed otherwise. This could come as part of UTM operation authorization. It can be special instructions at the start or during an operation. - PII protection MUST not be used if the UAS loses connectivity to the + PII protection MUST NOT be used if the UAS loses connectivity to the USS. The UAS always has the option to abort the operation if PII protection is disallowed. -11. References +12. References -11.1. Normative References +12.1. Normative References [I-D.ietf-drip-reqs] Card, S. W., Wiethuechter, A., Moskowitz, R., and A. Gurtov, "Drone Remote Identification Protocol (DRIP) Requirements", Work in Progress, Internet-Draft, draft- ietf-drip-reqs-18, 8 September 2021, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . -11.2. Informative References +12.2. Informative References [CTA2063A] ANSI, "Small Unmanned Aerial Systems Serial Numbers", 2019. [Delegated] European Union Aviation Safety Agency (EASA), "EU Commission Delegated Regulation 2019/945 of 12 March 2019 on unmanned aircraft systems and on third-country operators of unmanned aircraft systems", 2019. @@ -901,20 +900,28 @@ United States Federal Aviation Administration (FAA), "Unmanned Aircraft System (UAS) Traffic Management (UTM) Concept of Operations (V2.0)", 2020, . [FS_AEUA] "Study of Further Architecture Enhancement for UAV and UAM", 2021, . + [I-D.ietf-drip-auth] + Wiethuechter, A., Card, S., and R. Moskowitz, "DRIP + Authentication Formats & Protocols for Broadcast Remote + ID", Work in Progress, Internet-Draft, draft-ietf-drip- + auth-04, 20 December 2021, + . + [Implementing] European Union Aviation Safety Agency (EASA), "EU Commission Implementing Regulation 2019/947 of 24 May 2019 on the rules and procedures for the operation of unmanned aircraft", 2019. [LAANC] United States Federal Aviation Administration (FAA), "Low Altitude Authorization and Notification Capability", n.d., . @@ -951,55 +958,60 @@ [RFC7033] Jones, P., Salgueiro, G., Jones, M., and J. Smarr, "WebFinger", RFC 7033, DOI 10.17487/RFC7033, September 2013, . [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T. Henderson, "Host Identity Protocol Version 2 (HIPv2)", RFC 7401, DOI 10.17487/RFC7401, April 2015, . - [RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access - Protocol (RDAP) Query Format", RFC 7482, - DOI 10.17487/RFC7482, March 2015, - . - - [RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the - Registration Data Access Protocol (RDAP)", RFC 7483, - DOI 10.17487/RFC7483, March 2015, - . - [RFC7484] Blanchet, M., "Finding the Authoritative Registration Data (RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March 2015, . [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . [RFC8004] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004, October 2016, . [RFC8005] Laganier, J., "Host Identity Protocol (HIP) Domain Name System (DNS) Extension", RFC 8005, DOI 10.17487/RFC8005, October 2016, . + [RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital + Signature Algorithm (EdDSA)", RFC 8032, + DOI 10.17487/RFC8032, January 2017, + . + [RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, May 2018, . [RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", STD 94, RFC 8949, DOI 10.17487/RFC8949, December 2020, . + [RFC9082] Hollenbeck, S. and A. Newton, "Registration Data Access + Protocol (RDAP) Query Format", STD 95, RFC 9082, + DOI 10.17487/RFC9082, June 2021, + . + + [RFC9083] Hollenbeck, S. and A. Newton, "JSON Responses for the + Registration Data Access Protocol (RDAP)", STD 95, + RFC 9083, DOI 10.17487/RFC9083, June 2021, + . + [TS-22.825] 3GPP, "Study on Remote Identification of Unmanned Aerial Systems (UAS)", n.d., . [U-Space] European Organization for the Safety of Air Navigation (EUROCONTROL), "U-space Concept of Operations", 2019, .