DRIP Entity Tag (DET) Identity Management Architecture

Internet-Draft	DETIM Architecture	December 2023
Wiethuechter & Reid	Expires 6 June 2024	[Page]

Abstract

This document describes the high level architecture for the registration and discovery of DRIP Entity Tags (DETs) using DNS. Discovery of DETs and their artifacts are through DRIP specific DNS structures and standard DNS methods. A general overview of the interfaces required between involved components is described in this document with future supporting documents giving technical specifications.¶

1. Introduction

Registries are fundamental to Unmanned Aircraft System (UAS) Remote ID (RID). Only very limited operational information can be Broadcast, but extended information is sometimes needed. The most essential element of information is the UAS ID, the unique key for lookup of extended information in relevant registries (see Figure 4 of [RFC9434]).¶

While it is expected that DRIP Identity Management Entity (DIME) functions will be integrated with UAS Service Suppliers (USS) (Appendix A.2 of [RFC9434]), who will provide DIME-like functions is not yet determined in most, and is expected to vary between, jurisdictions. However this evolves, the essential DIME-like functions (including the management of identifiers (such as the DRIP Entity Tag (DET))) are expected to remain the same, so are specified herein.¶

While most data to be sent via Broadcast RID (Section 1.2.1 of [RFC9434]) or Network RID (Section 1.2.2 of [RFC9434]) is public, much of the extended information in registries will be private. As discussed in Section 7 of [RFC9434], Authentication, Attestation, Authorization, Access Control, Accounting, Attribution, and Audit (AAA) for registries is essential, not just to ensure that access is granted only to strongly authenticated, duly authorized parties, but also to support subsequent attribution of any leaks, audit of who accessed information when and for what purpose. As specific AAA requirements will vary by jurisdictional regulation, provider choices, customer demand, etc., they are left to specification in policies, which should be human readable to facilitate analysis and discussion, and machine readable to enable automated enforcement, using a language amenable to both (e.g., eXtensible Access Control Markup Language (XACML)).¶

The intent of the access control requirements on registries is to ensure that no member of the public would be hindered from accessing public information, while only duly authorized parties would be enabled to access private information. Mitigation of Denial of Service (DoS) attacks and refusal to allow database mass scraping would be based on those behavior, not on identity or role of the party submitting the query per se, but querant identity information might be gathered (by security systems protecting DRIP implementations) on such misbehavior.¶

Registration under DRIP is vital to manage the inevitable collisions in the hash portion of the DET (Section 9.5 of [RFC9374]). Forgery of a DET is still possible, but including it as a part of a public registration mitigates this risk.¶

This document creates the DRIP registration and discovery ecosystem focusing on the DET. This SHOULD support all components in the ecosystem (e.g., Unmanned Aircraft (UA), Registered Assigning Authority (RAA), Hierarchical HIT Domain Authority (HDA), Ground Control Station (GCS), and USS) that can use a DET.¶

This document uses the Concise Data Definition Language (CDDL) [RFC8610] for describing the registration data.¶

2. Abstract Process and Reasoning

In DRIP each entity (DIME, Operator, UA, etc.) is expected to generate a DET [RFC9374] on the local device their key is expected to be used. These are registered with a Public Information Registry (e.g. DNS) within the hierarchy along with whatever data is required by the cognizant CAA and the DIME. Any Personally Identifiable Information (PII) is stored in a Private Information Registry protected through industry practice AAA or stronger. In response, the entity will obtain an endorsement from the DIME proving such registration.¶

Manufacturers that wish to participate in DRIP should not only support DRIP as a Session ID type for their aircraft but could also generate a DET then encode it as a Serial Number (Section 4.2 of [RFC9374]). This would allow aircraft under CAA mandates to fly only ID Type 1 (Serial Number) could still use DRIP and most of its benefits. Even if DRIP is not supported for Serial Numbers by a Manufacturer it is hoped that they would still run a DIME to store their Serial Numbers and allow look ups for generic model information. This look up could be especially helpful in UTM for Situational Awareness when an aircraft flying with a Serial Number is detected and allow for an aircraft profile to be displayed.¶

Operators are registered with a number of registries or their regional RAA. This acts as a verification check when a user performs other registration operations; such as provisioning an aircraft with a new Session ID. It is an open question if an Operator registers to their CAA (the RAA's direct HDA) or multiple USS's (HDA's). PII of the Operator would vary based on the CAA they are under and the DIME.¶

Finally, aircraft that support using a DET would provision per flight to a USS, proposing a DET to the DIME to generate a binding between the aircraft (Session ID, Serial Number, and Operational Intent), operator and DIME. The aircraft then follows [drip-auth] to meet various requirements from [RFC9153] during a flight.¶

4. DIME Roles

[RFC9434] defines the DRIP Identity Management Entity (DIME) as an entity that vets Claims and/or Evidence from a registrant and delivers, to successful registrations, Endorsements and/or Certificates in response. The DIME encompasses various logical components and can be classified to serve a number of different roles, which are detailed in the following subsections. The general hierarchy of these initial roles (some highly specialized and predetermined for the UAS use case) are illustrated in Figure 1.¶

                +----------+
                |   Apex   o--------.
                +-o------o-+        |
                  |      |          |
******************|******|**********|******************
                  |      |          |
            +-----o-+  +-o-----+  +-o-----+
RAAs        |  MCA  |  |  INN  |  |  RAA  |
            +---o---+  +---o---+  +---o---+
                |          |          |
****************|**********|**********|****************
                |          |          |
            +---o---+  +---o---+  +---o---+
HDAs        |  MAA  |  |  HDA  |  |  HDA  |
            +-------+  +-------+  +-------+

Figure 1: DIME Roles and Hierarchy

4.1. Apex

The Apex is a special DIME role that holds the values of RAA=0-3 and HDA=0. It serves as the branch point from the larger DNS system in which DETs are defined. The Apex is the owner of the IPv6 prefix portion of the DET associated with it (2001:30/28) which is assigned by IANA from the special IPv6 address space for ORCHIDs.¶

The Apex manages all delegations and allocations of the DET's RAA to various parties. Allocations of RAAs SHOULD be done in contiguous groups of 4.¶

Table 1
RAA Decimal Range	RAA Hex Range	Status
0 - 3	0x0000 - 0x0003	Apex
4 - 3999	0x0004 - 0x0F9F	ISO 3166-1 Countries (Section 4.2.1)
4000 - 16375	0x1000 - 0x3FFF	Reserved
16376 - 16383	0x3FF8 - 0x3FFF	DRIP WG Experimental Use

Note: that the first column of this table is decimal values not hexadecimal.¶

RAA values of 0 (0x0000) to 3 (0x0003) are reserved to the Apex exclusively.¶

The Experimental range of 16376 (0x3FF8) to 16383 (0x3FFF), eight (8) RAAs, is allocated to the DRIP working group itself. 16376 to 16379 are setup by DRIP experts to act as RAAs for potential HDA users to test against. RAA 16376 is already "in use" with driptesting.org. The rest of the range (16377 to 16383) are reserved to be allocate by the DRIP experts to agencies that wish to test.¶

4.2. Registered Assigning Authority (RAA)

RAA's are the upper hierarchy in DRIP (denoted by a 14-bit field, i.e. 16,384 RAAs, of an DET). An RAA is a business or organization that manages a DIME of HDAs (Section 4.3). Most are contemplated to be Civil Aviation Authorities (CAA), such as the Federal Aviation Authority (FAA), that then delegate HDAs to manage their National Air Space (NAS). This is does not preclude other entities to operate an RAA if the Apex allows it.¶

An RAA must provide a set of services to allocate HDAs to organizations. It must have a public policy on what is necessary to obtain an HDA. It must maintain a DNS zone minimally for discovering HID RVS servers. All RAA's have a single reserved HDA value: 0 (0x0000) for itself to support various functions or services. Other HDA values can be allocated or reserved per RAA policy.¶

4.2.1. ISO 3166-1 Numeric Nations (INN)

The RAA range of 4 (0x0004) to 3999 (0x0F9F) are reserved for CAAs using the ISO 3166-1 Numeric Nation Code. The RAA can be derived from the ISO 3166-1 numeric code by multiplying the value by 4 (i.e. raa_code = iso_code * 4). Four contiguous values (raa_code + 0, raa_code + 1, raa_code + 2 and raa_code + 3) are used in a single allocation. The inverse (RAA to ISO) works out as: iso_code = floor(raa_code / 4).¶

As an example the United States has an ISO 3166-1 Numeric Code of 840. This derives the following RAAs: 3360, 3361, 3362 and 3363.¶

It should be noted that the range of codes from 900 to 999 are defined as "user assigned code elements" without specific claimant predefined in the RAA space. Withdrawn and other special codes also do not have predetermined claimants.¶

How a CAA handles their 4 allocations are out of scope of this document. Control of these values are expected to be claimed by their respective owner. How a claim is vetted and validated is out of scope of this document. Protection against fraudulent claims of one of these values is out of scope for this document.¶

Note: A single entity may control more than one NAS (for example LU and BE being covered by Skeyes.be) and would manage two allocation spaces. How this is claimed and handled is out of scope for this document.¶

4.3. Hierarchial HIT Domain Authority (HDA)

An HDA may be an USS, ISP, or any third party that takes on the business to register the actual entities that need DETs. This includes, but is not limited to UA, GCS, UAS Operators and infrastructure (such as Supplemental Data Service Providers). It should also provide needed UAS services including those required for HIP-enabled devices (e.g. RVS).¶

A primary function of HDAs for DRIP, in the context of UAS RID is the binding between a UAS Session ID (for DRIP the DET) and the UA Serial Number. The Serial Number MUST have its access protected to allow only authorized parties to obtain it. The Serial Number MUST be protected in a way only the authorized party can decrypt. As part of the UTM system HDAs can also hold a binding between a UAS ID (Serial Number or Session ID) and an Operational Intent. They may either be a direct logical part of a UAS Service Supplier (USS) or be a UTM wide service to USS's.¶

The HDA is a 14-bit field (16,384 HDAs per RAA) of a DET assigned by an RAA. An HDA should maintain a set of RVS servers for UAS clients that may use HIP. How this is done and scales to the potentially millions of customers are outside the scope of this document. This service should be discoverable through the DNS zone maintained by the HDA's RAA.¶

An RAA may assign a block of values to an individual organization. This is completely up to the individual RAA's published policy for delegation. Such policy is out of scope.¶

5. DIME Architecture

The DIME, in any of its roles (Section 4), is comprised of a number of logical components that are depicted in Figure 2. Any of these components could be delegated to other entities as a service both co-located or remote. For example:¶

The Name Server component could be handled by a well-established DNS registrar/registry with the DRIP Provisioning Agent (DPA) (Section 5.1) interfacing to them¶
- Either the DPA or the Registry/Name Server interfaces to the DRIP Information Agent (DIA)¶
The DPA, Registry, and Name Server may all be co-located in one implementation with an interface to a DIA offered by another organization from any one of the co-located components¶

+--------------------+
| Registering Client |
+---------o----------+
          |
**********|******************************************************
*         |     DRIP Identity Management Entity (DIME)          *
*         |                                                     *
*  +------o-------+      +-------------+      +--------------+  *
*  | DRIP         |      |             |      |              |  *
*  | Provisioning o------o             |      |              |  *
*  | Agent (DPA)  |      |             |      |              |  *
*  +-------o------+      |             |      |              |  *
*          |             |             |      |              |  *
*          |             | DRIP        |      | Registration |  *
*  +-------o--+          | Information o------o Data         |  *
*  | Registry o----------o Agent (DIA) |      | Directory    |  *
*  +-------o--+          |             |      | Service      |  *
*          |             |             |      | (RDDS)       |  *
*          |             |             |      |              |  *
*  +-------o----------+  |             |      |              |  *
*  | Name Server (NS) |  |             |      |              |  *
*  +------o-----------+  +-----o-------+      +------o-------+  *
*         |                    |                     |          *
*         |                    |                     |          *
**********|********************|*********************|***********
          |                    |                     |
          |            +-------o-------+             |
          '------------o Lookup Client o-------------'
                       +---------------+

Figure 2: DIME Logical Components

5.1. DRIP Provisioning Agent (DPA)

The DPA performs the important task of vetting information coming from clients wishing to register and then delegate (internally or externally) various items to other components in the DIME.¶

A standard interface MUST be provided for clients to access. An HTTPS based interface is RECOMMENDED. This interface specification is out of scope for this document.¶

There MUST be an interface from the DPA to a Registry (Section 5.2) component which handles the DNS specific requirements of the DIME as defined by the Registry. There MAY also be interface from the DPA to a DRIP Information Agent (Section 5.4) as defined by the DIA.¶

+-------------+
| Registering |
|   Client    |
+------o------+
       |
       | HTTPS
       |
       |
    +--o--+           +-----+
    | DPA o-----------o DIA |
    +--o--+    TBD    +-----+
       |
       |
       | HTTPS or EPP
       |
+------o---+
| Registry |
+----------+

Figure 3: DPA Interface Mapping

5.2. Registry

The Registry component handles all the required DNS based requirements of the DIME to function for DRIP. This includes the registration and maintenance of various DNS Resource Records.¶

A standardized interface MUST be implemented for interactions with the DPA (Section 5.1). This interface MAY be over HTTPS using JSON/CBOR encoding or MAY use the Extensional Provisioning Protocol (EPP) [RFC5730]. The detailed specification of either of these interfaces is out of scope for this document.¶

There MAY be interface from the Registry to a DRIP Information Agent (Section 5.4) as defined by the DIA.¶

    +-----+
    | DPA |
    +--o--+
       |
       | HTTPS or EPP
       |
       |
+------o---+           +-----+
| Registry o-----------o DIA |
+-----o----+    TBD    +-----+
      |
      |
      | TBD
      |
  +---o--+
  |  NS  |
  +------+

Figure 4: Registry Interface Mapping

5.3. Name Server (NS)

The interface of the Name Server to any component (nominally the Registry) in a DIME is out of scope as typically they are implementation specific.¶

Author Note: This may be very important here as we should not preclude a USS from running his own Name Server but they are not DNS experts and will need guidance or at least pointers to it to not mess it up. Such as SOA and NS formats to allow delegation if acting as an RAA.¶

+----------+
| Registry |
+-----o----+
      |
      |
      | TBD
      |
  +---o--+
  |  NS  |
  +--o---+
     |
     |
     | DNS Query/Response
     |
+----o----------+
| Lookup Client |
+---------------+

Figure 5: Name Server Interface Mapping

5.4. DRIP Information Agent (DIA)

The DIA is the main component handling requests for information from entities outside of the DIME. Typically this is when an Observer looks up a Session ID from an UA and gets pointed to the DIA to obtain information not available publicly (i.e. via DNS).¶

The information contained in the DIA is generally more oriented around the Operator of a given UAS and is thus classified as Personally Identifiable Information (PII). To protect the privacy of an Operator of the UAS this information is not publicly accessible and is only available behind policy driven differentiated access mechanisms (see Section 7).¶

For DRIP, the Registration Data Access Protocol (RDAP) ([RFC7480], [RFC9082] and [RFC9083]) is the selected protocol to provide policy driven differentiated access for queries of information from clients.¶

There MUST be a standardized interface for the DPA or Registry to add, update or delete information into the DIA. Specific details for these interfaces are out of scope for this document.¶

An interface defined by the Registration Data Directory Service (RDDS) (Section 5.5) is also required as specified by the RDDS.¶

                         +-----+
                         | DPA |
                         +--o--+
                            |
                            |
                            | TBD
                            |
  +----------+    TBD    +--o--+             +------+
  | Registry o-----------o DIA o-------------o RDDS |
  +----------+           +--o--+     TBD     +------+
                            |
                            |
                       RDAP |
                            |
                    +-------o-------+
                    | Lookup Client |
                    +---------------+

Figure 6: DIA Interface Mapping

5.5. Registration Data Directory Service (RDDS)

This is the primary information database for the DIA. An interface MUST be provided to the DIA but its specification is out of scope for this document.¶

   +-----+
   | DIA |
   +--o--+
      |
      |
      | TBD
      |
  +---o--+
  | RDDS |
  +--o---+
     |
     |
     | RDAP
     |
+----o----------+
| Lookup Client |
+---------------+

Figure 7: RDDS Interface Mapping

6. Registration/Provisioning Process

The general process for a registering party is as follows:¶

Verify input Endorsement(s) from registering party¶
Check for collision of DET and HI¶
Populate Registry/Name Server with resource record(s)¶
Populate RDDS via DIA with PII and other info¶
Generate and return Endorsement(s)¶

In the following subsections an abbreviated form of Section 5 using co-located components is used to describe the flow of information. The data elements being transmitted between entities is marked accordingly in each figure for the specific examples.¶

Each section has an associated appendix (Appendix D) containing DNS examples.¶

6.1. Operator

Provided either by USS or CAA run HDAs. Regulation might require interaction between them. An Operator can request that certain information normally generated and provisioned into DNS be omitted due to privacy concerns.¶

    +----------+
    | Operator |
    +--o---o---+
       |   ^
   (a) |   | (b)
       |   |
*******|***|*****************************
*      |   |    DIME:HDA                *
*      |   |                            *
*      v   |             +----------+   *
*   +--o---o--+          |          |   *
*   |   DPA   o--------->o          |   *
*   +----o----+   (d)    |          |   *
*        |               |          |   *
*        | (c)           | DIA/RDDS |   *
*        v               |          |   *
*   +----o--------+      |          |   *
*   | Registry/NS |      |          |   *
*   +-------------+      |          |   *
*                        +----------+   *
*                                       *
*****************************************

(a) Operator Information,
    Operator Self-Endorsement
(b) Success Code,
    Generic Endorsement: HDA on Operator
(c) HIP RR, DET RR, TLSA RR, URI RR, PTR RR
(d) Operator Information

Note: (c) MAY be requested by the Operator
      to be omitted due to PII concerns.

Figure 8: Example DIME:HDA with Operator (DET) Registration

The definition of Operator Information is out of scope of this document and left to local regulations (both in its format and contents).¶

6.2. Session ID

Session IDs are generally handled by HDAs. In Figure 9 the UAS comprises of an unmanned aircraft and a Ground Control Station (GCS). Both parties are involved in the registration process.¶

    +---------+
    |   UAS   |
    +--o---o--+
       |   ^
   (a) |   | (b)
       |   |
*******|***|*****************************
*      |   |    DIME: HDA               *
*      |   |                            *
*      v   |             +----------+   *
*   +--o---o--+          |          |   *
*   |   DPA   o--------->o          |   *
*   +----o----+   (d)    |          |   *
*        |               |          |   *
*        | (c)           | DIA/RDDS |   *
*        v               |          |   *
*   +----o--------+      |          |   *
*   | Registry/NS |      |          |   *
*   +-------------+      |          |   *
*                        +----------+   *
*                                       *
*****************************************

(a) Mutual Endorsement: HDA on GCS,
    Generic Endorsement: GCS on UA,
    Session ID Information
(b) Success Code,
    Broadcast Endorsement: HDA on UA,
    Generic Endorsement: HDA on UAS
(c) HIP RR, DET RR, TLSA RR, URI RR, PTR RR
(d) Session ID Information

Figure 9: Example DIME:HDA with Session ID (DET) Registration

Through mechanisms not specified in this document the Operator should have methods (via the GCS) to instruct the unmanned aircraft onboard systems to generate a keypair, DET and Self-Endorsement: UA. The Self-Endorsement: UA is extracted by the Operator onto the GCS.¶

The GCS is already pre-provisioned and registered to the DIME with its own keypair, DET, Self-Endorsement: GCS and Generic Endorsement: HDA on GCS. The GCS creates a new Generic Endorsement: GCS on UA and also creates Mutual Endorsement: HDA on GCS. These new endorsements along with Session ID Information are sent to the DIME via a secure channel.¶

The GCS injects the Broadcast Endorsement: HDA on UA securely into the unmanned aircraft. Endorsement: HDA on GCS is securely stored by the GCS.¶

Note: in Figure 9 the Session ID Information is expected to contain the Serial Number along with other PII specific information (such as UTM data) related to the Session ID.¶

Session ID Information is defined as the current model:¶

sessionid_info = {
    serial: tstr .size 20,
    session_id: tstr,
    operational_intent: tstr,
    intent_src: tstr,
    operator_id: tstr,
    session_context: tstr,
    * tstr: any
}

Future standards or implementations MAY add other keys to this list (for local features and/or local regulation).¶

6.2.1. UA Based Session ID

There may be some unmanned aircraft that have their own Internet connectivity allowing them to register a Session ID themselves without outside help from other devices such as a GCS. When such a system is in use its imperative that the Operator has some method to create the Generic Endorsement: Operator on UA to send to the DIME. The process and methods to perform this are out of scope for this document but MUST be done in a secure fashion.¶

6.2.2. UAS Based Session ID

Most unmanned aircraft will not have their own Internet connectivity but will have a connection to a GCS. Typically a GCS is an application on a user device (such as smartphone) that allow the user to fly their aircraft. For the Session ID registration the DIME MUST be provided with an Generic Endorsement: GCS on UA which implies there is some mechanism extracting and inserting information from the unmanned aircraft to the GCS. These methods MUST be secure but are out of scope for this document.¶

With this system it is also possible to have the GCS generate the DET based Session ID and insert it securely into the unmanned aircraft after registration is done. This is NOT RECOMMENDED as this invalidates the objective of the asymmetric cryptography in the underlying DET as the private key MAY get in the possession of another entity other than the unmanned aircraft. See Section 12.2 for more details.¶

6.3. Child DIME

Handled by the Apex and RAA's. This is an endpoint that handles dynamic registration (or key roll-over) of lower-level DIMEs (RAAs to Apex and HDAs to RAAs) in the hierarchy.¶

    +---------------+
    |   DIME: HDA   |
    +--o---o--------+
       |   ^
   (a) |   | (b)
       |   |
*******|***|*****************************
*      |   |    DIME: RAA               *
*      |   |                            *
*      v   |             +----------+   *
*   +--o---o--+          |          |   *
*   |   DPA   o--------->o          |   *
*   +----o----+   (d)    |          |   *
*        |               |          |   *
*        | (c)           | DIA/RDDS |   *
*        v               |          |   *
*   +----o--------+      |          |   *
*   | Registry/NS |      |          |   *
*   +-------------+      |          |   *
*                        +----------+   *
*                                       *
*****************************************

(a) Self-Endorsement: HDA,
    HDA Information or
    Generic Endorsement: old HDA, new HDA
(b) Success Code,
    Broadcast Endorsement: RAA on HDA
(c) HIP RR, DET RR, TLSA RR, URI RR, PTR RR
(d) HDA Information

Figure 10: Example DIME:RAA with DIME:HDA Registration

It should be noted that this endpoint DOES NOT hand out dynamically RAA/HDA values to systems that hit the endpoint. This is done out-of-band through processes specified by local regulations and performed by cognizant authorities. The endpoint MUST NOT accept queries it is not previously informed of being expected via mechanisms not defined in this document.¶

It is OPTIONAL to implement this endpoint. This MAY be used to handle lower-level DIME key roll-over.¶

7. Differentiated Access Process

Per [RFC9434] all information classified as public is stored in a datastore protected using some form of differentiated access (i.e. AAA) to satisfy REG-2 from [RFC9153].¶

Differentiated access, as a process, is a requirement for DIMEs as defined in [RFC9153] by the combination of PRIV-1, PRIV-3, PRIV-4, REG-2 and REG-4. [RFC9434] further elaborates on the concept by citing RDAP (from [RFC7480], [RFC9082] and [RFC9083]) as a potential means of fulfilling this requirement.¶

Typically the cognizant authority is the primary querant of private information from a DIME if a Session ID is reported (the case of the owner of the private information is ignored for the moment). This capability MAY be delegated to other parties at the authorities discretion (be it to a single user or many), thus requiring a flexible system to delegate, determine and revoke querent access rights for information. XACML MAY be a good technology choice for this flexibility.¶

It is noted by the authors that as this system scales the problem becomes a, well known and tricky, key management problem. While recommendations for key management are useful they are not necessarily in scope for this document as best common practices around key management should already be mandated and enforced by the cognizant authorities in their existing systems. This document instead focuses on finding a balance for generic wide-spread interoperability between DIMEs with authorities and their existing systems in a Differentiated Access Process (DAP).¶

A system where cognizant authorities would require individual credentials to each HDA is not scalable, nor practical. Any change in policy would require the authority to interact with every single HDA (active or inactive) to grant or revoke access; this would be tedious and prone to mistakes. A single credential for a given authority is also strongly NOT RECOMMENDED due to the security concerns it would entail if it leaked.¶

A zero-trust model would be the most appropriate for a DAP; being highly flexible and robust. Most authorities however use "oracle" based systems with specific user credentials and the oracle knowing the access rights for a given user. This would require the DAP the have some standard mechanism to locate and query a given oracle for information on the querent to determine if access is granted.¶

DRIP has no intention to develop a new "art" of key management, instead hoping to leverage existing systems and be flexible enough to adapt as new ones become popular.¶

8. DRIP in the Domain Name System

Per [RFC9434] all information classified as public is stored in the DNS to satisfy REG-1 from [RFC9153].¶

The apex for domain names MUST be under the administrative control of ICAO, the international treaty organization providing the critical coordination platform for civil aviation. ICAO SHOULD be responsible for the operation of the DNS-related infrastructure for these domain name apexes. It MAY chose to run that infrastructure directly or outsource it to competent third parties or some combination of the two. ICAO SHOULD specify the technical and administrative criteria for the provision of these services: contractual terms (if any), reporting, uptime, SLAs (if any), DNS query handling capacity, response times incident handling, complaints, law enforcement interaction and so on.¶

The delegation of civil aviation authorities to RAAs is already done per Section 4.2.1 using their ISO 3166-1 Numeric Codes. Since these are public, any entity can stand up an RAA with that value. ICAO SHOULD be the root of trust in a Endorsement or certificate chain that provides validation of any of these specific RAAs, in the ISO RAA range, thus protecting against bad actors standing up fraudulent RAAs. This also ensures DRIP complies with national law and regulation since these are matters of national sovereignty.¶

Each national aviation authority SHOULD be responsible for the operation of the DNS-related infrastructure for their delegated subdomains. As with the domain apexes overseen by ICAO, each national aviation authority MAY chose to run that infrastructure directly or outsource it to competent third parties or some combination of the two. National aviation authorities SHOULD specify the technical and administrative criteria for the provision of these services: contractual terms (if any), reporting, uptime, SLAs (if any), DNS query handling capacity, response times, incident handling, complaints, law enforcement interaction and so on. These are National Matters where national law/regulation prevail. National policy and regulations will define how long DNS data are stored or archived.¶

DNSSEC is strongly RECOMMENDED (especially for RAA-level and higher zones). When a DIME decides to use DNSSEC they SHOULD define a framework for cryptographic algorithms and key management [RFC6841]. This may be influenced by frequency of updates, size of the zone, and policies.¶

8.1. DRIP Entity Tags

The REQUIRED mechanism is to place any information into ip6.arpa when using a DET. Since the DET is an IPv6 address it can be nibble-reversed and used in the zone, per standard conventions.¶

The prefix 2001:30/28 is registered with IANA [RFC9374] and 3.0.0.1.0.0.2.ip6.arpa - the corresponding reverse domain - SHOULD be under the administrative control of the Apex. In addition to the DNS infrastructure for 3.0.0.1.0.0.2.ip6.arpa, the Apex SHOULD be responsible for the allocation of IPv6 addresses in this prefix. An addressing plan will need to be developed.¶

Distribution of HHIT (IPv6 address) blocks SHOULD be done using the 14-bit RAA space as a framework. The Apex SHOULD allocate blocks to each entity who can then assign them to HDAs in accordance with local law and policy. All HDAs MUST have an IPv6 address in 2001:30/28. A discrete zone SHOULD be delegated for each HDA. These MUST contain an DET resource record (Section 8.1.1) for itself.¶

Reverse lookups of these IPv6 addresses will translate the address into a domain name in the manner defined in [RFC1886]. However, these lookups will query for, depending on what is required: HIP, DET, TLSA, URI, or PTR RRTypes.¶

8.1.1. DET Resource Record

Author Note: This section is very much a WIP, comments are welcome.¶

The DET Resource Record is a metadata record for various bits of DRIP specific information that isn't available in pre-existing DNS RR Types (such as URI or HIP).¶

<domain> DET IN ( DET TYPE STATUS HID SN Endorsement )

DET = Base16 DET
TYPE = enumeration of Type of DET
STATUS = enumeration of Status of DET
HID = HID Abbreviation
SN = Serial Number
Endorsement = Broadcast Endorsement

8.1.1.1. Type

This field is a single byte with values defined in Section 11.2.2.¶

It is envisioned that there may be many types of DETs in use. In some cases it may be helpful to understand the DETs role in the ecosystem like described in [drip-dki].¶

8.1.1.2. Status

This field is a single byte with values defined in Section 11.2.3.¶

A DET can go through various states during its life-cycle in the ecosystem. It is helpful for a querant to understand the current status as a further requirement for verification.¶

8.1.1.3. HID Abbreviation

This field is an fixed length ASCII encoded string of 20 bytes null padded. When not included the field MUST be filled with nulls.¶

The specific contents of this field are not defined here, but a recommendation/example can be found in Appendix A.¶

8.1.1.4. Serial Number

This field is an fixed length ASCII encoded string of 20 bytes null padded [CTA2063A]. When not included the field MUST be filled with nulls.¶

This covers the "public mapping to DET" when a user/manufacturer already has a Serial Number that can not change and wishes to do DRIP Authentication.¶

8.1.1.5. Endorsement

This field is the binary encoded Broadcast Endorsement (Appendix C.3) of the DET. This object is a fixed length of 136 bytes.¶

9. Endorsements

DRIP Endorsements are defined in a CDDL [RFC8610] structure (Figure 11) that can be encoded to CBOR, JSON or have their CDDL keys removed and be sent as a binary blob. When the latter is used very specific forms are defined with naming conventions to know the data fields and their lengths for parsing and constrained environments. CBOR is the preferred encoding format.¶

The CDDL was derived from the more specific structure developed for [drip-auth]. As such the structures found in [drip-auth], such as the UA Signed Evidence and the contents of DRIP Link (known as a Broadcast Endorsement), are a subset of the below definition in a strict binary form.¶

Appendix C specifies specific Endorsement structures for the UAS RID use-case.¶

Note: this section uses the term HHIT instead of DET as the Endorsements are designed to be generic and re-useable for other HHIT use-cases. Specific use-cases SHOULD add new keys for each section (if required) and define the valid keys and encoding forms for their use-case.¶

9.1. Endorsement Structure

endorsement = {
    ; TODO: add tag for self-describing type or leave up to cbor?
    scope: {
        vnb: number,
        vna: number,
        * tstr => any
    },
    evidence: bstr,
    endorser: {
        identity: {
            hhit: bstr .size 16, ? hi: bstr // * tstr => any
        },
        signature: {
            sig: bstr,
            * tstr => any
        }
    }
}

Figure 11: Endorsement CDDL

9.1.1. Scope

The scope section is more formally "the scope of validity of the endorsement". The scope can come in various forms but MUST always have a "valid not before" (vnb) and "valid not after" (vna) timestamps.¶

Other forms of the scope could for example be a 4-dimensional volume definition. This could be in raw latitude, longitude, altitude pairs or may be a URI pointing to scope information. Additional scope fields are out of scope for this document and should be defined for specific Endorsement structures if they are desired.¶

9.1.2. Evidence

The evidence section contain a byte string of evidence. Specific content of evidence (such as subfields, length and ordering) is defined in specific Endorsement structures.¶

9.1.3. Identity

The identity section is where the main identity information of the signer of the Endorsement is found. The identity can take many forms such as a handle to the identity (e.g. an HHIT), or can include more explicit data such as the public key (e.g. an HI). Other keys, for different identifiers, can be provided and MUST be defined in their specific Endorsement.¶

The length of the hi can be determined when using hhit by decoding the provided IPv6 address. The prefix will inform of the ORCHID construction being used, which informs the locations of the OGA ID in the address. The OGA ID will then inform the user of the key algorithm selected which has the key length defined.¶

9.1.4. Signature

The signature section contain the signature data for the Endorsement. The signature itself MUST be provided under the sig key. Other forms or data elements could also be present in the signature section if specified in a specific Endorsement. Signatures MUST be generated using the preceding sections in their binary forms (i.e. as a bytestring with no keys).¶

10. X.509 Certificates

10.1. Certificate Policy and Certificate Stores

X.509 certificates are optional for the DRIP entities covered in this document. DRIP endpoint entities (EE) (i.e., UA, GCS, and Operators) may benefit from having X.509 certificates. Most of these certificates will be for their DET and some will be for other UAS identities. To provide for these certificates, some of the other entities (e.g. USS) covered in this document will also have certificates to create and manage the necessary PKI structure.¶

Three certificate profiles are defined, with examples, and explained in [drip-dki]. Each has a specific role to play and an EE may have its DET enrolled in all of them. There is a 'Lite' profile that would work well enough on constrained communication links for those instances where various issues push the use of X.509. There is a 'Basic; profile that is more in line with [RFC5280] recommendations, but is still small enough for many constrained environments. Finally there is a profile to directly add DET support into the civil/general aviation certificates as discussed below.¶

A Certificate Authority (CA) supporting DRIP entities MAY adhere to the ICAO's Aviation Common Certificate Policy (ACCP). The CA(s) supporting this CP MUST either be a part of the ACCP cross-certification or part of the ACCP CA Trust List. It is possible that future versions of the ACCP will directly support the DRIP Basic profile.¶

Authors Note: ACCP is ICAO Doc 10169 Aviation Common Certificate Policy (ACCP). I can't get a url for that, but so far these is no changes from v 0.93 of the old IATF CP; changes are in the works then will be posted, so continue to reference IATF CP¶

EEs may use their X.509 certificates, rather than their rawPublicKey (i.e. HI) in authentication protocols (as not all may support rawPublicKey identities). Short lived DETs like those used for a single operation or even for a day's operations may not benefit from X.509. Creating then almost immediately revoking these certificates is a considerable burden on all parts of the system. Even using a short notAfter date will not completely mitigate the burden of managing these certificates. That said, many EEs will benefit to offset the effort. It may also be a regulator requirement to have these certificates. Finally, certificates can provide the context of use for a DET (via policy constraint OIDs).¶

Typically an HDA either does or does not issue a certificate for all its DETs. An RAA may specifically have some HDAs for DETs that do not want/need certificates and other HDAs for DETs that do need them. These types of HDAs could be managed by a single entity thus providing both environments for its customers.¶

It is recommended that DRIP X.509 certificates be stored as DNS TLSA Resource Records, using the DET as the lookup key. This not only generally improves certificate lookups, but also enables use of DANE [RFC6698] for the various servers in the UTM and particularly DIME environment and DANCE [dane-clients] for EEs (e.g. [drip-secure-nrid-c2]). All DRIP certificates MAY alternatively be available via RDAP. LDAP/OCSP access for other UTM and ICAO uses SHOULD also be provided.¶

10.2. Certificate Management

PKIX standard X.509 issuance practices should be used. The certificate request SHOULD be included in the DET registration request. A successful DET registration then MUST include certificate creation, store, and return to the DET registrant. It is possible that the DET registration is actually an X.509 registration. For example, PKIX CSR may be directly used and the DET registration and Endorsement creation are a addition to this process. Further ACME may be directly extendable to provide the DET registration.¶

Note that CSRs do not include the certificate validityDate; adding that is done by the CA. If in the registration process, the EE is the source of notBefore and notAfter dates, they need to be sent along with the CSR.¶

Certificate revocation will parallel DET revocation. TLSA RR MUST be deleted from DNS and RDAP, LDAP, and OCSP return revoked responses. CRLs SHOULD be maintained per the CP.¶

10.3. Examples

For full examples of X.509 Certificates and the process to use them see [drip-dki].¶

10.4. Alternative Certificate Encoding

The CBOR Encoded X.509 Certificates (C509 Certificates) [cbor-cert] provides a standards-based approach to reduce the size of X.509 certificates both on-the-wire and in storage. The PKI-Lite RAA certificate example in Appendix B.2 is 331 bytes. The matching C509 certificate is 183 bytes. This sort of difference may have significant impact both on UAS storage requirements and over-the-air transmission impact.¶

C509 provides two approaches for encoding X.509:¶

An invertible CBOR re-encoding of DER encoded X.509 certificates [RFC5280], which can be reversed to obtain the original DER encoded X.509 certificate.¶
Natively signed C509 certificates, where the signature is calculated over the CBOR encoding instead of over the DER encoding as in 1. This removes the need for ASN.1 and DER parsing and the associated complexity but they are not backwards compatible with implementations requiring DER encoded X.509.¶

The invertible CBOR encoding may be sufficient for most needs. The CBOR objects clearly indicate which approach was used, so that the receiver can properly process the C509 object. For interoperability in DRIP, it is recommended that invertible CBOR encoding be used.¶

Using the invertible CBOR encoding is achieved through in-line libraries that convert in the desired direction. Since it is not expected that DNS protocols to implement this conversion, the DET RR SHOULD contain the normal X.509 DER encoding. The CBOR encoding MAY be used, but operational experience will be needed to see if there are measurable gains in doing so.¶

11. IANA Considerations

11.1. Delegation of Nibble Reversed IPv6 Prefix

For DRIP to function in a interoperable way the easiest way to allow look up of DETs is through the already existing ip6.arpa domain structure (as defined in this document). Here IPv6 addresses are nibble reversed and usually have PTR records.¶

With DRIP the prefix 2001:30/28 has been allocated by IANA already for DRIP use. However its representative reverse domain in ip6.arpa has not.¶

There are a number of questions in this area for DRIP:¶

What organization would have administrative control over the nibble-reversed ip6.arpa block for 2001:30/28?¶
- How do they obtain this and from whom?¶
- What is the SLA between IANA/ICANN and the administrative organization for nibble-reversed 2001:30/28?¶
What organization would have technical control (i.e. day to day operations) over the nibble-reversed ip6.arpa block for 2001:30/28?¶
How are delegation/allocation of further nibble-reversed sub-blocks from 2001:30/28 handled by the administrative organization?¶
- This is partly covered in this document already (Apex->RAA->HDA)¶
- What is the SLA between the administrative organization and sub-organizations given delegations/allocations? This might be more general guidelines than an actual SLA?¶
What goes into a nibble-reversed ip6.arpa domain for DRIP at each level?¶

This is not an exhaustive list of questions, this is more to get discussion going.¶

11.2. IANA DRIP Registry

11.2.1. Endorsement Fields

This document requests a new registry for Endorsement fields under the DRIP registry group.¶

Endorsement Fields:: list of field keys to be used in an Endorsement and what section(s) they can be used in. Future additions to this registry are to be made through First Come First Served (Section 4.4 of [RFC8126]). The following values are defined:¶

Table 2
Field Name	Type	Useable Sections	Description
vna	number	scope	Valid Not After, UTC Unix Timestamp
vnb	number	scope	Valid Not Before, UTC Unix Timestamp
hhit	bstr	identity	Hierarchial Host Identity Tag (HHIT), fixed size of 16
hi	bstr	identity	Host Identity (HI)
sig	bstr	signature	Signature

11.2.2. DET Type

This document requests a new registry for DET Type under the DRIP registry group.¶

DET Type:: numeric, 8 bit, field of the DET RR to encode the DET Type. Future additions to this registry are to be made through First Come First Served (Section 4.4 of [RFC8126]). The following values are defined:¶

Table 3
Type	Value	Description
Not Defined	0	-
Endpoint Entity (EE)	1	-
Issuer CA	2	-
Authentication CA	3	-

11.2.3. DET Status

This document requests a new registry for DET Status under the DRIP registry group.¶

DET Status:: numeric, 8 bit, field of the DET RR to encode the DET Status. Future additions to this registry are to be made through First Come First Served (Section 4.4 of [RFC8126]). The following values are defined:¶

Table 4
Status	Value	Description
Not Defined	0	-
Inactive	1	-
Active	2	-

12. Security Considerations

12.1. Key Rollover & Federation

During key rollover the DIME MUST inform all children and parents of the change - using best standard practices of a key rollover.¶

A DET has a natural ability for a single DIME to hold different cryptographic identities under the same HID values. This is due to the lower 64-bits of the DET being a hash of the public key and the HID of the DET being generated. As such during key rollover, only the lower 64-bits would change and a check for a collision would be required.¶

This attribute could also allow for a single DIME to be "federated" across multiple DETs sharing the same HID value. This method of deployment has not been thoroughly studied at this time. An endpoint such as in Section 6.3 is a possible place to have these functions.¶

12.2. DET Generation

Author Note: is this section valid anymore? Perhaps we hard specify that devices ONLY generate on their own hardware instead of "out-sourcing" as this section implies.¶

Under the FAA [NPRM], it is expecting that IDs for UAS are assigned by the UTM and are generally one-time use. The methods for this however are unspecified leaving two options.¶

Option 1:¶

The entity generates its own DET, discovering and using the RAA and HDA for the target DIME. The method for discovering a DIME's RAA and HDA is out of scope here. This allows for the device to generate an DET to send to the DIME to be accepted (thus generating the required Self-Endorsement) or denied.¶

Option 2:¶

The entity sends to the DIME its HI for it to be hashed and result in the DET. The DIME would then either accept (returning the DET to the device) or deny this pairing.¶

Keypairs are expected to be generated on the device hardware it will be used on. Due to hardware limitations and connectivity it is acceptable, though not recommended, under DRIP to generate keypairs for the Aircraft on Operator devices and later securely inject them into the Aircraft. The methods to securely inject and store keypair information in a "secure element" of the Aircraft is out of scope of this document.¶

15. References

15.1. Normative References

[RFC2119]: Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174]: Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8610]: Birkholz, H., Vigano, C., and C. Bormann, "Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[RFC9153]: Card, S., Ed., Wiethuechter, A., Moskowitz, R., and A. Gurtov, "Drone Remote Identification Protocol (DRIP) Requirements and Terminology", RFC 9153, DOI 10.17487/RFC9153, February 2022, <https://www.rfc-editor.org/info/rfc9153>.
[RFC9374]: Moskowitz, R., Card, S., Wiethuechter, A., and A. Gurtov, "DRIP Entity Tag (DET) for Unmanned Aircraft System Remote ID (UAS RID)", RFC 9374, DOI 10.17487/RFC9374, March 2023, <https://www.rfc-editor.org/info/rfc9374>.
[RFC9434]: Card, S., Wiethuechter, A., Moskowitz, R., Zhao, S., Ed., and A. Gurtov, "Drone Remote Identification Protocol (DRIP) Architecture", RFC 9434, DOI 10.17487/RFC9434, July 2023, <https://www.rfc-editor.org/info/rfc9434>.

15.2. Informative References

[cbor-cert]: Mattsson, J. P., Selander, G., Raza, S., Höglund, J., and M. Furuhed, "CBOR Encoded X.509 Certificates (C509 Certificates)", Work in Progress, Internet-Draft, draft-ietf-cose-cbor-encoded-cert-07, 20 October 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-cose-cbor-encoded-cert-07>.
[CTA2063A]: "ANSI/CTA 2063-A Small Unmanned Aerial Systems Numbers", September 2019, <https://shop.cta.tech/products/small-unmanned-aerial-systems-serial-numbers>.
[dane-clients]: Huque, S. and V. Dukhovni, "TLS Client Authentication via DANE TLSA records", Work in Progress, Internet-Draft, draft-ietf-dance-client-auth-02, 12 May 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-dance-client-auth-02>.
[drip-auth]: Wiethuechter, A., Card, S. W., and R. Moskowitz, "DRIP Entity Tag Authentication Formats & Protocols for Broadcast Remote ID", Work in Progress, Internet-Draft, draft-ietf-drip-auth-41, 4 December 2023, <https://datatracker.ietf.org/doc/html/draft-ietf-drip-auth-41>.
[drip-dki]: Moskowitz, R. and S. W. Card, "The DRIP DET public Key Infrastructure", Work in Progress, Internet-Draft, draft-moskowitz-drip-dki-09, 23 October 2023, <https://datatracker.ietf.org/doc/html/draft-moskowitz-drip-dki-09>.
[drip-secure-nrid-c2]: Moskowitz, R., Card, S. W., Wiethuechter, A., and A. Gurtov, "Secure UAS Network RID and C2 Transport", Work in Progress, Internet-Draft, draft-moskowitz-drip-secure-nrid-c2-13, 19 September 2023, <https://datatracker.ietf.org/doc/html/draft-moskowitz-drip-secure-nrid-c2-13>.
[NPRM]: "Notice of Proposed Rule Making on Remote Identification of Unmanned Aircraft Systems", December 2019.
[RFC1886]: Thomson, S. and C. Huitema, "DNS Extensions to support IP version 6", RFC 1886, DOI 10.17487/RFC1886, December 1995, <https://www.rfc-editor.org/info/rfc1886>.
[RFC5280]: Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, <https://www.rfc-editor.org/info/rfc5280>.
[RFC5730]: Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009, <https://www.rfc-editor.org/info/rfc5730>.
[RFC6698]: Hoffman, P. and J. Schlyter, "The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August 2012, <https://www.rfc-editor.org/info/rfc6698>.
[RFC6841]: Ljunggren, F., Eklund Lowinder, AM., and T. Okubo, "A Framework for DNSSEC Policies and DNSSEC Practice Statements", RFC 6841, DOI 10.17487/RFC6841, January 2013, <https://www.rfc-editor.org/info/rfc6841>.
[RFC7480]: Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the Registration Data Access Protocol (RDAP)", STD 95, RFC 7480, DOI 10.17487/RFC7480, March 2015, <https://www.rfc-editor.org/info/rfc7480>.
[RFC8126]: Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>.
[RFC9082]: Hollenbeck, S. and A. Newton, "Registration Data Access Protocol (RDAP) Query Format", STD 95, RFC 9082, DOI 10.17487/RFC9082, June 2021, <https://www.rfc-editor.org/info/rfc9082>.
[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, <https://www.rfc-editor.org/info/rfc9083>.

Appendix A. HID Abbreviation Recommendation

On receiver devices a DET can be translated to a more human readable form such as: {RAA Abbreviation} {HDA Abbreviation} {Last 4 Characters of DET Hash}. An example of this would be US FAA FE23.¶

To support this DIMEs are RECOMMENDED to have an abbreviation that could be used for this form. These abbreviations SHOULD be a maximum of six characters (for each section) in length. Spaces MUST NOT be used and be replaced with either underscores (_) or dashes (-).¶

The concatenation of {RAA Abbreviation} and {HDA Abbreviation} with a space between them can be what fills in the HID field of the DET RR in Section 8.1.1.¶

For RAAs allocated in the ISO range Section 4.2.1, the RAA abbreviation SHOULD be set to the ISO 3166-1 country code (either Alpha-2 or Alpha-3). A common abbreviation for an RAAs four allocated RAA values are out of scope. Other documents such as [drip-dki] may have more specific recommendations or requirements.¶

If a DIME does not have an abbreviation or it can not be looked up then the receiver MUST use the uppercase 4-character hexadecimal encoding of the field it is missing when using this form.¶

Appendix C. DRIP Endorsements for UAS

C.1. Generic Endorsement

generic_endorsement = {
    scope: {
        vnb: number,
        vna: number
    },
    evidence: bstr,
    endorser: {
        identity: {
            hhit: bstr .size 16
        },
        signature: {
            sig: bstr
        }
    }
}

Figure 12: Generic Endorsement CDDL

evidence is a binary string with specified contents (in format and ordering) by specific use-cases. As an example this format is used by [drip-auth] to support Authentication over F3411 constrained links. evidence data is defined by [drip-auth] for DRIP Wrapper, Manifest and Frame formats.¶

C.2. Self Endorsement

self_endorsement = {
    scope: {

        vnb: number,
        vna: number
    },
    evidence: bstr,
    endorser: {
        identity: {
            hhit: bstr .size 16
        },
        signature: {
            sig: bstr
        }
    }
}

Figure 13: Self Endorsement CDDL

Used during registration process as an input. evidence is filled with the corresponding HI of the hhit.¶

0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+---------------+---------------+
|                              VNB                              |
+---------------+---------------+---------------+---------------+
|                              VNA                              |
+---------------+---------------+---------------+---------------+
|                                                               |
|                                                               |
|                                                               |
|                              HI                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
+---------------+---------------+---------------+---------------+
|                                                               |
|                             HHIT                              |
|                                                               |
|                                                               |
+---------------+---------------+---------------+---------------+
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                           Signature                           |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
+---------------+---------------+---------------+---------------+

Figure 14: Self Endorsement Binary

TODO

Figure 15: Self Endorsement CBOR

C.3. Broadcast Endorsement

broadcast_endorsement = {
    scope: {
        vnb: number,
        vna: number
    },
    evidence: bstr,
    endorser: {
        identity: {
            hhit: bstr .size 16
        },
        signature: {
            sig: bstr
        }
    }
}

Figure 16: Broadcast Endorsement CDDL

Defined by [drip-auth] in a binary format to support Authentication over F3411 constrained links. Used in the DRIP Link format. A required output of registration to a DIME at any level. evidence is a binary string of the concatenation of a child entities (e.g. a UA) DET/HHIT and its associated HI. hhit is of the parent entity (e.g. a DIME).¶

 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+---------------+---------------+
|                              VNB                              |
+---------------+---------------+---------------+---------------+
|                              VNA                              |
+---------------+---------------+---------------+---------------+
|                                                               |
|                            HHIT of                            |
|                             Child                             |
|                                                               |
+---------------+---------------+---------------+---------------+
|                                                               |
|                                                               |
|                                                               |
|                             HI of                             |
|                             Child                             |
|                                                               |
|                                                               |
|                                                               |
+---------------+---------------+---------------+---------------+
|                                                               |
|                            HHIT of                            |
|                            Parent                             |
|                                                               |
+---------------+---------------+---------------+---------------+
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                           Signature                           |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
|                                                               |
+---------------+---------------+---------------+---------------+

Figure 17: Broadcast Endorsement Binary

TODO

Figure 18: Broadcast Endorsement CBOR