RFC 9942
CBOR Object Signing and Encryption (COSE) Receipts
RFC 9942: CBOR Object Signing and Encryption (COSE) Receipts 🧾✨
Okay bestie, here's the paperwork vibe check 📋💅. This is RFC 9942, a Standards Track document from the Internet Engineering Task Force (IETF), published June 2026 with ISSN 2070-1721. The authors are O. Steele (Tradeverifyd), H. Birkholz (Fraunhofer SIT), A. Delignat-Lavaud (Microsoft), and C. Fournet (Microsoft). The title block doesn't list any documents this one obsoletes or updates, so nothing gets replaced or patched here 🫶.
Table of Contents 📑
- 1. Introduction
- 1.1. Requirements Notation
- 2. New COSE Header Parameters
- 3. Terminology
- 4. VDSs in CBOR
- 4.1. Structures
- 4.2. Proofs
- 4.3. Usage
- 4.4. Profiles
- 4.4.1. Registration Requirements
- 5. RFC9162_SHA256
- 5.1. Verifiable Data Structure
- 5.2. Inclusion Proof
- 5.2.1. Receipt of Inclusion
- 5.3. Consistency Proof
- 5.3.1. Receipt of Consistency
- 6. Privacy Considerations
- 6.1. Log Length
- 6.2. Header Parameters
- 7. Security Considerations
- 7.1. Choice of Signature Algorithms
- 7.2. Validity Period
- 7.3. Status Updates
- 8. IANA Considerations
- 8.1. COSE Header Parameter
- 8.2. VDS Registries
- 8.2.1. Expert Review
- 8.2.2. Templates and Initial Contents
- 9. References
- 9.1. Normative References
- 9.2. Informative References
- Acknowledgements
- Contributors
- Authors' Addresses
Abstract 💭
COSE Receipts let you prove properties of a Verifiable Data Structure (VDS) to a verifier 🔍. VDSs and their Proof Types unlock security goodies like minimal disclosure, transparency, and non-equivocation 🦋. Transparency keeps trust alive over time, and it's already been used for certificates, end-to-end encrypted messaging, and supply chain security 🔒. This spec makes concise transparency systems possible by building on Concise Binary Object Representation (CBOR) and COSE. To prove it's extensible, it also gives CBOR encodings for Merkle inclusion and consistency proofs 🌸.
Status of This Memo 📜
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.
Info about the current status, any errata, and how to send feedback lives at https://www.rfc-editor.org/info/rfc9942 🔗.
Copyright Notice ⚖️
Copyright (c) 2026 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, because they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions, and they are provided without warranty as described in the Revised BSD License 📄.
1. Introduction ✨
COSE Receipts are signed proofs 🖊️. They carry metadata about certain states of a Verifiable Data Structure (VDS), and those states were true when the COSE Receipt got issued. A receipt can prove that a document sits in a database (proof of inclusion), that a database is append-only (proof of consistency), that a smaller set of statements lives inside a big set of statements (proof of disclosure, which is a special case of proof of inclusion), or that certain data isn't in a database yet (proof of non-inclusion) 👀. Different VDSs can produce different Verifiable Data Structure Proofs (VDPs). Mixing all those representations of VDSs and VDPs makes life hard for implementers and creates interoperability headaches for transparency services 😭. So this document shows how to carry VDS and associated VDP types in unified Enveloped COSE Structures 🎀.
1.1. Requirements Notation
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 here 🔥.
2. New COSE Header Parameters 🎀
This document adds three new COSE header parameters 💜. They get introduced right up front in this section and then explained in more depth later on.
394: A COSE header parameter named "receipts" with a value type of array, where the array contains one or more COSE Receipts as specified in this document 🧾.
395: A COSE header parameter named "vds" (for Verifiable Data Structure), which conveys the algorithm identifier for a VDS. For the integers that identify VDSs, check out the registry in Section 8.2.2.1 📚.
396: A COSE header parameter named "vdp" (for VDPs), which conveys a map containing VDPs organized by Proof Type. For the integers that identify VDS Proof Types, check out the registry in Section 8.2.2.2 🦋.
3. Terminology 📖
The terms "header" and "payload" are defined in [STD96]. The term "claim" is defined in [RFC8392].
On top of that, this document uses the following terms:
CDDL: Concise Data Definition Language (CDDL) is defined in [RFC8610].
EDN: CBOR Extended Diagnostic Notation (EDN) is defined in [RFC8949], where it's called "diagnostic notation", and it gets revised in [CBOR-EDN] 🌈.
Entry: An entry in a VDS that proofs can be derived for 🧚.
Proof Type: A property you can get by verifying a given proof over one or more entries in a VDS. For example, a VDS like a binary Merkle Tree can support inclusion proofs, where each proof confirms that a given entry is included in a Merkle Tree root 🌳.
Proof Value: An encoding of a Proof Type in CBOR [RFC8949] 🍓.
Receipt: A COSE Single Signer Data Object, as defined in RFC 9052 of [STD96], containing the header parameters needed to convey one or more VDPs for an associated VDS 🧾💖.
Verifiable Data Structure (VDS): A data structure that supports one or more VDS Proof Types. This property describes an algorithm used to maintain a VDS, for example, a binary Merkle Tree algorithm 🌲.
Verifiable Data Structure Proof (VDP): A data structure used to convey Proof Types for proving different properties, such as authentication, inclusion, consistency, and freshness. Parameters can include multiple proofs of a given type or multiple types of proof (inclusion and consistency) 👑.
4. VDSs in CBOR 🌸
This section describes how VDPs are represented in [RFC8949]. For example, building a Merkle Tree leaf or an inclusion proof from a leaf to a Merkle Tree root might look different depending on which VDS you use 🙈. Those representation differences are needed for efficient verification, for unique security or privacy properties, and for compatibility with specific implementations. This document defines two extension points for enabling VDSs with COSE, and it gives concrete examples for the structures and proofs defined in Section 2.1.3 of [RFC9162] and Section 2.1.4 of [RFC9162]. The design of these structures is influenced by the conventions set up for COSE Keys 🔑.
4.1. Structures
Similar to COSE Key Types [IANA.cose_header-parameters], different VDSs support different algorithms 💅.
This document sets up a registry of VDS algorithms. Check Section 8.2.2.1 for the details 📚.
4.2. Proofs
Just like COSE Key Type Parameters [IANA.cose_header-parameters], EC2 keys (1: 2) require and give meaning to specific parameters, such as -1 (crv), -2 (x), -3 (y), and -4 (d). RFC9162_SHA256 (395: 1) supports both (-1) inclusion and (-2) consistency proofs ✨.
This document sets up a registry of VDS algorithm proofs. Check Section 8.2.2.2 for the details 🦋.
Proof Types are specific to their associated "Verifiable Data Structure". For example, different Merkle Trees might support different representations of inclusion proof or consistency proof. Implementers should not expect interoperability across "Verifiable Data Structures" 🥺. Security analysis MUST be conducted before migrating to new structures, so you can be sure the new security and privacy assumptions work for the use case 🚨.
Heads up: this doc is only part 1 of 4, so Section 4.3 (Usage) and everything after it comes in the next part 💖🦋
4.3. Usage 🎀
okay so this section is where the "receipts" header parameter gets registered 💅 It's number 394, and it lets Receipts ride along in the protected and unprotected headers of Enveloped COSE Structures 🦋
When the "receipts" header parameter shows up, the verifier MUST confirm that the associated VDS and VDPs match entries in the registries this specification sets up, including any values added in later registrations 🔥
Receipts MUST be tagged as COSE_Sign1 🏷️ ✨
Figure 1 shows how Receipts get tucked into a COSE_Sign1 data item 🧚
Signature_With_Receipt = #6.18(COSE_Sign1)
cose-label = int / text
cose-values = any
Protected_Header = {
* cose-label => cose-values
}
Unprotected_Header = {
&(receipts: 394) => [+ bstr .cbor Receipt]
* cose-label => cose-values
}
COSE_Sign1 = [
protected : bstr .cbor Protected_Header
unprotected : Unprotected_Header
payload : bstr / nil
signature : bstr
]
Receipt = Receipt_For_Inclusion / Receipt_For_Consistency
; Note the proof formats shown here are for RFC9162_SHA256.
; Other VDSs may have different proof formats.
Receipt_For_Inclusion = #6.18(Signed_Inclusion_Proof)
Signed_Inclusion_Proof = [
protected :
bstr .cbor RFC9162_SHA256_Inclusion_Protected_Header,
unprotected : RFC9162_SHA256_Inclusion_Unprotected_Header,
payload : bstr / nil,
signature : bstr
]
RFC9162_SHA256_Inclusion_Protected_Header = {
&(alg: 1) => int
&(vds: 395) => int
* cose-label => cose-values
}
RFC9162_SHA256_Inclusion_Unprotected_Header = {
&(vdp: 396) => RFC9162_SHA256_Verifiable_Inclusion_Proofs
* cose-label => cose-values
}
RFC9162_SHA256_Verifiable_Inclusion_Proofs = {
&(inclusion-proof: -1) => RFC9162_SHA256_Inclusion_Proofs
}
RFC9162_SHA256_Inclusion_Proofs = [
+ RFC9162_SHA256_Inclusion_Proof
]
RFC9162_SHA256_Inclusion_Proof =
bstr .cbor RFC9162_SHA256_Inclusion_Proof_Content
RFC9162_SHA256_Inclusion_Proof_Content = [
tree_size: uint,
leaf_index: uint,
inclusion_path:[ + bstr ]
]
Receipt_For_Consistency = #6.18(Signed_Consistency_Proof)
Signed_Consistency_Proof = [
protected :
bstr .cbor RFC9162_SHA256_Consistency_Protected_Header,
unprotected : RFC9162_SHA256_Consistency_Unprotected_Header,
payload : bstr / nil, ; Newer Merkle Tree root
signature : bstr
]
RFC9162_SHA256_Consistency_Protected_Header = {
&(alg: 1) => int,
&(vds: 395) => int,
* cose-label => cose-values
}
RFC9162_SHA256_Consistency_Unprotected_Header = {
&(vdp: 396) => RFC9162_SHA256_Verifiable_Consistency_Proofs
* cose-label => cose-values
}
RFC9162_SHA256_Verifiable_Consistency_Proofs = {
&(consistency-proof: -2) => RFC9162_SHA256_Consistency_Proofs
}
RFC9162_SHA256_Consistency_Proofs = [
+ RFC9162_SHA256_Consistency_Proof
]
RFC9162_SHA256_Consistency_Proof =
bstr .cbor RFC9162_SHA256_Consistency_Proof_Content
RFC9162_SHA256_Consistency_Proof_Content = [
tree_size_1: uint,
tree_size_2: uint,
consistency_path: [ + bstr ]
]Figure 1: CDDL for a COSE_Sign1 with Attached Receipts
Here's an informative EDN example too 🌸
/ cose-sign1 / 18([
/ protected / <<{
/ kid / 4 : h'bc297b51...e4edf0de',
/ algorithm / 1 : -7, # ES256
}>>,
/ unprotected / {
/ receipts / 394 : [
<</ cose-sign1 / 18([
/ protected / <<{
/ kid / 4 : h'abcdef12...34567890',
/ algorithm / 1 : -7, # ES256
/ vds / 395 : 1, # RFC9162_SHA256
}>>,
/ unprotected / {
/ proofs / 396 : {
/ inclusion / -1 : [
<<[
/ size / 9, / leaf / 8,
/ inclusion path /
[ h'7558a95f...e02e35d6' ]
]>>
],
},
},
/ payload / null,
/ signature / h'02d227ed...ccd3774f'
])>>,
<</ cose-sign1 / 18([
/ protected / <<{
/ kid / 4 : h'abcdef12...34567890',
/ algorithm / 1 : -7, # ES256
/ vds / 395 : 1, # RFC9162_SHA256
}>>,
/ unprotected / {
/ proofs / 396 : {
/ inclusion / -1 : [
<<[
/ size / 6, / leaf / 5,
/ inclusion path /
[ h'9352f974...4ffa7ce0',
h'54806f32...f007ea06' ]
]>>
],
},
},
/ payload / null,
/ signature / h'36581f38...a5581960'
])>>
],
},
/ payload / h'0167c57c...deeed6d4',
/ signature / h'2544f2ed...5840893b'
])Figure 2: An Example COSE Signature with Multiple Receipts
The exact shape of a COSE Receipt depends on the COSE_Sign1 payload and on the VDPs sitting in the COSE_Sign1 unprotected header 🫶 The CDDL for VDPs is different for each VDS. This document describes the proofs for RFC9162_SHA256 in the sections that follow ✨
4.4. Profiles 🌈
New VDSs might need a profile defined for them 👑 The payload in those definitions SHOULD be detached 🙈 Detached payloads make verifiers recompute the root from the proof, which protects against implementation errors where the signature checks out but the payload doesn't match the proof 💀 Proof signatures that define extra protected header parameters are encouraged to make those parameters mandatory, so claims get processed with their intended meaning 💜 One way to put this info into the COSE structure is the "typ" (type) header parameter; see [RFC9596] and the similar guidance in [RFC9597] 🦋
4.4.1. Registration Requirements 📝
Every VDS specification that wants a spot in this registry MUST define how to encode the VDS identifier and its Proof Types in CBOR 🍓 It also MUST define how to produce and consume the supported Proof Types 🔥 Section 5 is the example to follow 💅
If a specification supports a choice of hash algorithm, each supported algorithm needs its own IANA registration 🧚 For example, say you want SHA256 and SHA3_256 with Merkle inclusion proofs and Merkle consistency proofs defined in Section 2.1.3 of [RFC9162] and Section 2.1.4 of [RFC9162], respectively. Then both "RFC9162_SHA256" and "RFC9162_SHA3_256" need entries in the relevant IANA registries 🌸 This document only defines "RFC9162_SHA256" 🎀
5. RFC9162_SHA256 🌷
This section maps the data structure described in Section 2.1 of [RFC9162] onto the terminology defined in this document, using [RFC8949] and [RFC9053] 💖
5.1. Verifiable Data Structure 🌳
The integer identifier for this VDS is 1 ✨ The string identifier is "RFC9162_SHA256", which is a Merkle Tree that uses SHA256 as its hash algorithm (see Table 2) 💜 For a full description of this VDS, check out Section 2.1.1 of [RFC9162] 📚
5.2. Inclusion Proof 🦋
For a full description of this VDS Proof Type, see Section 2.1.3.1 of [RFC9162] 💅
The CBOR representation of an inclusion proof for RFC9162_SHA256 looks like this 👀
inclusion-proof-content = [
; tree size at current Merkle Tree root
tree-size: uint
; index of leaf in tree
leaf-index: uint
; path from leaf to current Merkle Tree root
inclusion-path: [ + bstr ]
]Figure 3: CBOR-Encoded Inclusion Proof for RFC9162_SHA256
The name leaf-index is used so it lines up with the naming in Section 2.1.3.2 of [RFC9162] 🫶
[RFC9162] only defines inclusion proofs for leaf nodes, and there's one rule you need to know 🚨
If leaf_index is greater than or equal to tree_size, then fail the
proof verification.The identifying index of a leaf node is relative to all the nodes in the tree size the proof was obtained for 🧠
5.2.1. Receipt of Inclusion 🎀
In a signed proof, the payload is the Merkle Tree root for the log at size tree-size 🌊 The protected header for an RFC9162_SHA256 inclusion proof signature looks like this 💅
protected-header-map = {
&(alg: 1) => int
&(vds: 395) => int
* cose-label => cose-value
}Figure 4: Protected Header for a Receipt of Inclusion
alg(label: 1): REQUIRED. Signature algorithm identifier. Value type:int. 🔐vds(label: 395): REQUIRED. VDS algorithm identifier. Value type:int. 🏷️
The unprotected header for an RFC9162_SHA256 inclusion proof signature looks like this 🧚
inclusion-proofs = [ + inclusion-proof ]
verifiable-proofs = {
&(inclusion-proof: -1) => inclusion-proofs
}
unprotected-header-map = {
&(vdp: 396) => verifiable-proofs
* cose-label => cose-value
}Figure 5: A VDP in an Unprotected Header
vdp(label: 396): REQUIRED. Verifiable Data Structure Proofs. Value type: Map. 🌸inclusion-proof(label: -1): REQUIRED. Inclusion proofs. Value type: Array of bstr. 💖
The payload of an RFC9162_SHA256 inclusion proof signature is the Merkle Tree Hash, as defined in [RFC9162] 🌈
Here's an EDN example of a Receipt with an inclusion proof for RFC9162_SHA256, using a detached payload (see Section 4.4) 🦋
/ cose-sign1 / 18([
/ protected / <<{
/ algorithm / 1 : -7, # ES256
/ vds / 395 : 1, # RFC9162_SHA256
}>>,
/ unprotected / {
/ proofs / 396 : {
/ inclusion / -1 : [
<<[
/ size / 20, / leaf / 17,
/ inclusion path /
[ h'fc9f050f...221c92cb',
h'bd0136ad...6b28cf21',
h'd68af9d6...93b1632b' ]
]>>
],
},
},
/ payload / null,
/ signature / h'de24f0cc...9a5ade89'
])Figure 6: Receipt of Inclusion
The VDS in the protected header is what lets you understand the inclusion proof structure in the unprotected header 🔑
Verification of the inclusion proof and signature happens in two steps, one after the other 🎯
- Inclusion Proof Verification: The verifier applies the inclusion proof to the bytes of a candidate entry. If that fails, the proof is invalid. If it works, the resulting Merkle Tree root becomes the COSE_Sign1 payload 🧩
- Signature Verification: The verifier checks the COSE_Sign1 signature. A successful check confirms the entry is included in the VDS; otherwise, the signature is invalid 🫧
5.3. Consistency Proof 🌷
For a full description of this VDS Proof Type, see Section 2.1.4.1 of [RFC9162] 💜
The CBOR representation of a consistency proof for RFC9162_SHA256 looks like this 📜
consistency-proof-content = [
; older Merkle Tree size
tree-size-1: uint
; newer Merkle Tree size
tree-size-2: uint
; path from older Merkle Tree to newer Merkle Tree
consistency-path: [ + bstr ]
]Figure 7: CBOR-Encoded Consistency Proof for RFC9162_SHA256
5.3.1. Receipt of Consistency 🧾✨
Okay so, in a signed consistency proof, the newer Merkle Tree root (the one proven to be consistent with an older Merkle Tree root) is a detached payload 🎀. It corresponds to the log at size tree-size-2. 🌸
The protected header for an RFC9162_SHA256 consistency proof signature is:
protected-header-map = {
&(alg: 1) => int
&(vds: 395) => int
* cose-label => cose-value
}Figure 8: Protected Header for a Receipt of Consistency
alg(label: 1): REQUIRED. Signature algorithm identifier. Value type:int. 💅vds(label: 395): REQUIRED. VDS algorithm identifier. Value type:int. 🦋
The unprotected header for an RFC9162_SHA256 consistency proof signature is:
consistency-proofs = [ + consistency-proof ]
verifiable-proofs = {
&(consistency-proof: -2) => consistency-proofs
}
unprotected-header-map = {
&(vdp: 396) => verifiable-proofs
* cose-label => cose-value
}vdp(label: 396): REQUIRED. VDPs. Value type: Map. 🧚consistency-proof(label: -2): REQUIRED. Consistency proofs. Value type: Array of bstr. 💜
The payload of an RFC9162_SHA256 consistency proof signature is: The newer Merkle Tree Hash as defined in [RFC9162]. 🔥
Here's an EDN example for a Receipt containing a consistency proof for RFC9162_SHA256 with a detached payload (see Section 4.4). It's giving full detail, bestie 👑:
/ cose-sign1 / 18([
/ protected / <<{
/ algorithm / 1 : -7, # ES256
/ vds / 395 : 1, # RFC9162_SHA256
}>>,
/ unprotected / {
/ proofs / 396 : {
/ consistency / -2 : [
<<[
/ old / 20, / new / 104,
/ consistency path /
[ h'e5b3e764...c4a813bc',
h'87e8a084...4f529f69',
h'f712f76d...92a0ff36',
h'd68af9d6...93b1632b',
h'249efab6...b7614ccd',
h'85dd6293...38914dc1' ]
]>>
],
},
},
/ payload / null,
/ signature / h'94469f73...52de67a1'
])Figure 9: Example Consistency Receipt
The VDS in the protected header is necessary to understand the consistency proof structure in the unprotected header. It's the key to reading the proof, so don't skip it! 🙈
The signature and consistency proof are verified in order. 📋
First, the verifier checks the signature on the COSE_Sign1. If the verification fails, the consistency proof is not checked. 🚫
Second, the consistency proof is checked by applying a previous inclusion proof to the consistency proof. If the verification fails, the append-only property of the VDS is not assured. 😭
This approach is specific to RFC9162_SHA256; different VDSs may not support consistency proofs. It is recommended that implementations return a single boolean result for Receipt-verification operations to reduce the chance of accepting a valid signature over an invalid consistency proof. Ngl, that single boolean is such a clean move 💅✨
6. Privacy Considerations 🔒
6.1. Log Length
Some structures and proofs leak the size of the log at the time of inclusion. In the case that a log only stores certain kinds of information, this can reveal details that could impact reputation. For example, if a transparency log only stored breach notices, a receipt for a breach notice would reveal the number of previous breaches at the time the notice was made transparent. The tea is spilled, iykyk 🍓
6.2. Header Parameters
Additional header parameters can reveal information about the transparency service or its log entries. The receipt producer MUST perform a privacy analysis for all mandatory fields in profiles based on this specification. This is a MUST, so no skipping it, periodt 🫶
7. Security Considerations 🛡️💀
See the Security Considerations sections of:
7.1. Choice of Signature Algorithms
A security analysis ought to be performed to ensure that the digital signature algorithm alg has the appropriate strength to secure receipts. Main character energy means the signature algorithm has to be strong enough to protect the receipts 💪
It is recommended to select signature algorithms that share cryptographic components with the VDS used; for example, both RFC9162_SHA256 and ES256 depend on the SHA256 hash function. It's giving matching vibes, literally 🎀
7.2. Validity Period
In some cases, receipts MAY include strict validity periods, for example, activation not too far in the future or expiration not too far in the past. See the iat, nbf, and exp claims in [RFC8392] for one way to accomplish this. The details of expressing validity periods are out of scope for this document. 🕰️
7.3. Status Updates
In some cases, receipts should be "revocable" or "suspendable" after being issued, regardless of their validity period. The details of expressing statuses are out of scope for this document. Not me being dramatic, but status changes are a whole thing 😭
8. IANA Considerations 📚
8.1. COSE Header Parameter
IANA has added the COSE header parameters defined in Section 2, and as listed in Table 1, to the "COSE Header Parameters" subregistry [IANA.cose_header-parameters] in the "CBOR Object Signing and Encryption (COSE)" registry group. These COSE header parameters fall in the 'Integer values from 256 to 65535' range (with a Specification Required registration procedure (see [RFC8126])). The Value Registry listed for "vds" is the "COSE Verifiable Data Structure Algorithm" subregistry. The map labels in the "vdp" are assigned from the "COSE Verifiable Data Structure Proofs" subregistry. ✨
+==========+=======+=======+============+==============+===========+
| Name | Label | Value | Value | Description | Reference |
| | | Type | Registry | | |
+==========+=======+=======+============+==============+===========+
| receipts | 394 | array | | Priority | RFC 9942, |
| | | | | ordered | Section 2 |
| | | | | sequence of | |
| | | | | CBOR encoded | |
| | | | | Receipts | |
+----------+-------+-------+------------+--------------+-----------+
| vds | 395 | int | COSE | Algorithm | RFC 9942, |
| | | | Verifiable | identifier | Section 2 |
| | | | Data | for | |
| | | | Structure | Verifiable | |
| | | | | Data | |
| | | | | Structures | |
| | | | | that is used | |
| | | | | to produce | |
| | | | | Verifiable | |
| | | | | Data | |
| | | | | Structure | |
| | | | | Proofs | |
+----------+-------+-------+------------+--------------+-----------+
| vdp | 396 | map | map key in | Location for | RFC 9942, |
| | | | COSE | Verifiable | Section 2 |
| | | | Verifiable | Data | |
| | | | Data | Structure | |
| | | | Structure | Proofs in | |
| | | | Proofs | COSE Header | |
| | | | | Parameters | |
+----------+-------+-------+------------+--------------+-----------+Table 1: Newly Registered COSE Header Parameters
8.2. VDS Registries
IANA has established the "COSE Verifiable Data Structure Algorithms" and "COSE Verifiable Data Structure Proofs" subregistries under a Specification Required policy as described in Section 4.6 of [RFC8126]. 📝
8.2.1. Expert Review
Expert reviewers (see [RFC8126]) should take into consideration the following points:
- Experts are advised to assign the next available positive integer for VDSs.
- Point squatting should be discouraged. Reviewers are encouraged to get sufficient information for registration requests to ensure that the usage is not going to duplicate one that is already registered and that the point is likely to be used in deployments.
- Specifications are required for all point assignments. Early allocation is permissible, see Section 2 of [RFC7120].
- It is not permissible to assign points in the "COSE Verifiable Data Structure Algorithms" registry for which no corresponding entry in the "COSE Verifiable Data Structure Proofs" registry exists, and vice versa.
- The change controller for related registrations of structures and proofs should be the same.
8.2.2. Templates and Initial Contents
8.2.2.1. COSE Verifiable Data Structure Algorithms Initial Registry Contents
Registration Template:
- Name: This is a descriptive name for the VDS that enables easier reference to the item.
- Value: This is the value used to identify the VDS.
- Description: This field contains a brief description of the VDS.
- Reference: This contains a pointer to the public specification for the VDS.
- Change Controller: For Standards Track RFCs, list the "IETF". For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included.
+================+=======+===============+============+===========+
| Name | Value | Description | Change | Reference |
| | | | Controller | |
+================+=======+===============+============+===========+
| Reserved | 0 | Reserved | | RFC 9942 |
+----------------+-------+---------------+------------+-----------+
| RFC9162_SHA256 | 1 | SHA256 Binary | IETF | Section |
| | | | | 2.1 of |
| | | | | [RFC9162] |
+----------------+-------+---------------+------------+-----------+Table 2: COSE Verifiable Data Structure Algorithms Initial Registry Contents
8.2.2.2. COSE Verifiable Data Structure Proofs Registry ✨
okay so this is the registry for the proof types, bestie 💅 every entry needs a template, and each template has these fields:
- Verifiable Data Structure: the value that identifies the related VDS 🧚
- Name: a descriptive name for the Proof Type, so it's easy to refer to the item 🎀
- Label: the value used to identify the VDS Proof Type 🏷️
- CBOR Type: the CBOR type for the value portion of the label 🔢
- Description: a brief description of the Proof Type 📝
- Reference: a pointer to the public specification for the Proof Type 🔗
- Change Controller: for Standards Track RFCs, list the "IETF". for everything else, give the name of the responsible party. other details (like a postal address, email address, or home page URI) may also be included 💌
the initial contents are in Table 3, and it's giving clean, tidy, organized 🌸
+==========+===========+=====+=====+===========+==========+=========+
|Verifiable|Name |Label|CBOR |Description|Change |Reference|
|Data | | |Type | |Controller| |
|Structure | | | | | | |
+==========+===========+=====+=====+===========+==========+=========+
|1 |inclusion |-1 |array|Proof of |IETF |RFC 9942,|
| |proofs | |(of |inclusion | |Section |
| | | |bstr)| | |5.2 |
+----------+-----------+-----+-----+-----------+----------+---------+
|1 |consistency|-2 |array|Proof of |IETF |RFC 9942,|
| |proofs | |(of |append-only| |Section |
| | | |bstr)|property | |5.3 |
+----------+-----------+-----+-----+-----------+----------+---------+Table 3: COSE Verifiable Data Structure Proofs Initial Registry Contents 🦋
9. References 📚
9.1. Normative References
[IANA.cose_header-parameters] IANA, "COSE Header Parameters", https://www.iana.org/assignments/cose. the source of truth for header parameters, so don't skip it 👀
[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.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", STD 94, RFC 8949, DOI 10.17487/RFC8949, December 2020, https://www.rfc-editor.org/info/rfc8949.
[RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE): Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053, August 2022, https://www.rfc-editor.org/info/rfc9053.
[RFC9162] Laurie, B., Messeri, E., and R. Stradling, "Certificate Transparency Version 2.0", RFC 9162, DOI 10.17487/RFC9162, December 2021, https://www.rfc-editor.org/info/rfc9162.
[RFC9596] Jones, M.B. and O. Steele, "CBOR Object Signing and Encryption (COSE) "typ" (type) Header Parameter", RFC 9596, DOI 10.17487/RFC9596, June 2024, https://www.rfc-editor.org/info/rfc9596.
[RFC9597] Looker, T. and M.B. Jones, "CBOR Web Token (CWT) Claims in COSE Headers", RFC 9597, DOI 10.17487/RFC9597, June 2024, https://www.rfc-editor.org/info/rfc9597.
[STD96] Internet Standard 96, https://www.rfc-editor.org/info/std96. at the time of writing, this STD is made up of the following 🍓
- Schaad, J., "CBOR Object Signing and Encryption (COSE): Structures and Process", STD 96, RFC 9052, DOI 10.17487/RFC9052, August 2022,
https://www.rfc-editor.org/info/rfc9052. - Schaad, J., "CBOR Object Signing and Encryption (COSE): Countersignatures", STD 96, RFC 9338, DOI 10.17487/RFC9338, December 2022,
https://www.rfc-editor.org/info/rfc9338.
9.2. Informative References
[CBOR-EDN] Bormann, C., "Concise Diagnostic Notation (CDN)", Work in Progress, Internet-Draft, draft-ietf-cbor-edn-literals-26, 15 June 2026, https://datatracker.ietf.org/doc/html/draft-ietf-cbor-edn-literals-26.
[RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January 2014, https://www.rfc-editor.org/info/rfc7120.
[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.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, May 2018, https://www.rfc-editor.org/info/rfc8392.
Acknowledgements 🫶
we would like to thank Maik Riechert, Jon Geater, Michael B. Jones, Mike Prorock, Ilari Liusvaara, and Amaury Chamayou for their contributions (some of which were substantial) to this document and to the initial set of implementations. you all are the real MVPs 👑
Contributors 🌈
Amaury Chamayou Microsoft United Kingdom Email: amaury.chamayou@microsoft.com
Steve Lasker Email: stevenlasker@hotmail.com
Robert Martin MITRE Corporation United States of America Email: ramartin@mitre.org
Monty Wiseman United States of America Email: mwiseman32@acm.org
Roy Williams United States of America Email: roywill@msn.com
Authors' Addresses 💜
Orie Steele Tradeverifyd United States of America Email: orie@or13.io
Henk Birkholz Fraunhofer SIT Rheinstrasse 75 64295 Darmstadt Germany Email: henk.birkholz@ietf.contact
Antoine Delignat-Lavaud Microsoft United Kingdom Email: antdl@microsoft.com
Cédric Fournet Microsoft United Kingdom Email: fournet@microsoft.com
📦 where this page comes from
- ietf: rfc9942 2026-06
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms