rfc9942v1.txt   rfc9942.txt 
Internet Engineering Task Force (IETF) O. Steele Internet Engineering Task Force (IETF) O. Steele
Request for Comments: 9942 Tradeverifyd Request for Comments: 9942 Tradeverifyd
Category: Standards Track H. Birkholz Category: Standards Track H. Birkholz
ISSN: 2070-1721 Fraunhofer SIT ISSN: 2070-1721 Fraunhofer SIT
A. Delignat-Lavaud A. Delignat-Lavaud
C. Fournet C. Fournet
Microsoft Microsoft
March 2026 April 2026
CBOR Object Signing and Encryption (COSE) Receipts CBOR Object Signing and Encryption (COSE) Receipts
Abstract Abstract
CBOR Object Signing and Encryption (COSE) Receipts prove properties CBOR Object Signing and Encryption (COSE) Receipts prove properties
of a Verifiable Data Structure (VDS) to a verifier. Verifiable Data of a Verifiable Data Structure (VDS) to a verifier. Verifiable Data
Structures and associated proof types enable security properties, Structures and associated Proof Types enable security properties,
such as minimal disclosure, transparency, and non-equivocation. such as minimal disclosure, transparency, and non-equivocation.
Transparency helps maintain trust over time and has been applied to Transparency helps maintain trust over time and has been applied to
certificates, end-to-end encrypted messaging systems, and supply certificates, end-to-end encrypted messaging systems, and supply
chain security. This specification enables concise transparency- chain security. This specification enables concise transparency-
oriented systems by building on Concise Binary Object Representation oriented systems by building on Concise Binary Object Representation
(CBOR) and COSE. The extensibility of the approach is demonstrated (CBOR) and COSE. The extensibility of the approach is demonstrated
by providing CBOR encodings for Merkle inclusion and consistency by providing CBOR encodings for Merkle inclusion and consistency
proofs. proofs.
Status of This Memo Status of This Memo
skipping to change at line 99 skipping to change at line 99
Acknowledgements Acknowledgements
Contributors Contributors
Authors' Addresses Authors' Addresses
1. Introduction 1. Introduction
COSE Receipts are signed proofs that include metadata about certain COSE Receipts are signed proofs that include metadata about certain
states of a Verifiable Data Structure (VDS) that are true when the states of a Verifiable Data Structure (VDS) that are true when the
COSE Receipt was issued. COSE Receipts can include proofs that a COSE Receipt was issued. COSE Receipts can include proofs that a
document is in a database (proof of inclusion), that a database is document is in a database (proof of inclusion), that a database is
append only (proof of consistency), that a smaller set of statements append-only (proof of consistency), that a smaller set of statements
are contained in a large set of statements (proof of disclosure, a are contained in a large set of statements (proof of disclosure, a
special case of proof of inclusion), or that certain data is not yet special case of proof of inclusion), or that certain data is not yet
present in a database (proof of non-inclusion). Different VDSs can present in a database (proof of non-inclusion). Different VDSs can
produce different Verifiable Data structure Proofs (VDP). The produce different Verifiable Data structure Proofs (VDP). The
combination of representations of various VDSs and VDP can combination of representations of various VDSs and VDP can
significantly increase the burden for implementers and create significantly increase the burden for implementers and create
interoperability challenges for transparency services. This document interoperability challenges for transparency services. This document
describes how to convey VDS and associated VDP types in unified COSE describes how to convey VDS and associated VDP types in unified COSE
envelopes. envelopes.
skipping to change at line 124 skipping to change at line 124
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. New COSE Header Parameters 2. New COSE Header Parameters
This document defines three new COSE header parameters, which are This document defines three new COSE header parameters, which are
introduced up front in this section and elaborated on later in this introduced up front in this section and elaborated on later in this
document. document.
394: A COSE header parameter named receipts with a value type of 394: A COSE header parameter named "receipts" with a value type of
array where the array contains one or more COSE Receipts as array where the array contains one or more COSE Receipts as
specified in this document. specified in this document.
395: A COSE header parameter named vds (for Verifiable Data 395: A COSE header parameter named "vds" (for Verifiable Data
Structure), which conveys the algorithm identifier for a Structure), which conveys the algorithm identifier for a
Verifiable Data Structure. Correspondingly, see Section 8.2.2.1 Verifiable Data Structure. Correspondingly, see Section 8.2.2.1
for a registry defining the integers used to identify Verifiable for a registry defining the integers used to identify Verifiable
Data Structures. Data Structures.
396: A COSE header parameter named vdp (for Verifiable Data 396: A COSE header parameter named "vdp" (for Verifiable Data
Structure Proofs), which conveys a map containing Verifiable Data Structure Proofs), which conveys a map containing Verifiable Data
Structure Proofs organized by proof type. Correspondingly, see Structure Proofs organized by Proof Type. Correspondingly, see
Section 8.2.2.2 for a registry defining the integers used to Section 8.2.2.2 for a registry defining the integers used to
identify Verifiable Data Structure proof types. identify Verifiable Data Structure Proof Types.
3. Terminology 3. Terminology
CDDL: Concise Data Definition Language (CDDL) is defined in CDDL: Concise Data Definition Language (CDDL) is defined in
[RFC8610]. [RFC8610].
EDN: CBOR Extended Diagnostic Notation (EDN) is defined in EDN: CBOR Extended Diagnostic Notation (EDN) is defined in
[RFC8949], where it is referred to as "diagnostic notation", and [RFC8949], where it is referred to as "diagnostic notation", and
is revised in [CBOR-EDN]. is revised in [CBOR-EDN].
Verifiable Data Structure (VDS): A data structure that supports one Verifiable Data Structure (VDS): A data structure that supports one
or more Verifiable Data Structure Proof Types. This property or more Verifiable Data Structure Proof Types. This property
describes an algorithm used to maintain a Verifiable Data describes an algorithm used to maintain a Verifiable Data
Structure, for example, a binary Merkle tree algorithm. Structure, for example, a binary Merkle Tree algorithm.
Verifiable Data Structure Proofs (VDP): A data structure used to Verifiable Data Structure Proofs (VDP): A data structure used to
convey proof types for proving different properties, such as convey Proof Types for proving different properties, such as
authentication, inclusion, consistency, and freshness. Parameters authentication, inclusion, consistency, and freshness. Parameters
can include multiple proofs of a given type or multiple types of can include multiple proofs of a given type or multiple types of
proof (inclusion and consistency). proof (inclusion and consistency).
Proof Type: A property that can be obtained by verifying a given Proof Type: A property that can be obtained by verifying a given
proof over one or more entries in a Verifiable Data Structure. proof over one or more entries in a Verifiable Data Structure.
For example, a VDS, such as a binary Merkle tree, can support For example, a VDS, such as a binary Merkle Tree, can support
proofs of type "inclusion" where each proof confirms that a given inclusion proofs where each proof confirms that a given entry is
entry is included in a Merkle root. included in a Merkle Tree root.
Proof Value: An encoding of a Proof Type in CBOR [RFC8949]. Proof Value: An encoding of a Proof Type in CBOR [RFC8949].
Entry: An entry in a Verifiable Data Structure for which proofs can Entry: An entry in a Verifiable Data Structure for which proofs can
be derived. be derived.
Receipt: A COSE object, as defined in [RFC9052], containing the Receipt: A COSE Single Signer Data Object, as defined in [RFC9052],
header parameters necessary to convey VDP for an associated VDS. containing the header parameters necessary to convey one or more
VDP for an associated VDS.
4. Verifiable Data Structures in CBOR 4. Verifiable Data Structures in CBOR
This section describes representations of Verifiable Data Structure This section describes representations of Verifiable Data Structure
Proofs in [RFC8949]. For example, construction of a Merkle tree leaf Proofs in [RFC8949]. For example, construction of a Merkle Tree leaf
or an inclusion proof from a leaf to a Merkle root might have several or an inclusion proof from a leaf to a Merkle Tree root might have
different representations, depending on the Verifiable Data Structure several different representations, depending on the Verifiable Data
used. Differences in representations are necessary to support Structure used. Differences in representations are necessary to
efficient verification, unique security or privacy properties, and support efficient verification, unique security or privacy
for compatibility with specific implementations. This document properties, and for compatibility with specific implementations.
defines two extension points for enabling Verifiable Data Structures This document defines two extension points for enabling Verifiable
with COSE and provides concrete examples for the structures and Data Structures with COSE and provides concrete examples for the
proofs defined in Section 2.1.3 of [RFC9162] and Section 2.1.4 of structures and proofs defined in Section 2.1.3 of [RFC9162] and
[RFC9162]. The design of these structures is influenced by the Section 2.1.4 of [RFC9162]. The design of these structures is
conventions established for COSE Keys. influenced by the conventions established for COSE Keys.
4.1. Structures 4.1. Structures
Similar to COSE Key Types [IANA.cose_header-parameters], different Similar to COSE Key Types [IANA.cose_header-parameters], different
Verifiable Data Structures support different algorithms. Verifiable Data Structures support different algorithms.
This document establishes a registry of Verifiable Data Structure This document establishes a registry of Verifiable Data Structure
algorithms; see Section 8.2.2.1 for details. algorithms; see Section 8.2.2.1 for details.
4.2. Proofs 4.2. Proofs
Similar to COSE Key Type Parameters [IANA.cose_header-parameters], as Similar to COSE Key Type Parameters [IANA.cose_header-parameters], as
EC2 keys (1: 2) require and give meaning to specific parameters, such EC2 keys (1: 2) require and give meaning to specific parameters, such
as -1 (crv), -2 (x), -3 (y), -4 (d), RFC9162_SHA256 (395: 1) supports as -1 (crv), -2 (x), -3 (y), -4 (d), RFC9162_SHA256 (395: 1) supports
both (-1) inclusion and (-2) consistency proofs. both (-1) inclusion and (-2) consistency proofs.
This document establishes a registry of Verifiable Data Structure This document establishes a registry of Verifiable Data Structure
Proofs; see Section 8.2.2.2 for details. Proofs; see Section 8.2.2.2 for details.
Proof types are specific to their associated "Verifiable Data Proof Types are specific to their associated "Verifiable Data
Structure"; for example, different Merkle trees might support Structure"; for example, different Merkle Trees might support
different representations of "inclusion proof" or "consistency different representations of inclusion proof or consistency proof.
proof". Implementers should not expect interoperability across Implementers should not expect interoperability across "Verifiable
"Verifiable Data Structures". Security analysis MUST be conducted Data Structures". Security analysis MUST be conducted prior to
prior to migrating to new structures to ensure the new security and migrating to new structures to ensure the new security and privacy
privacy assumptions are acceptable for the use case. assumptions are acceptable for the use case.
4.3. Usage 4.3. Usage
This document registers a new COSE Header Parameter receipts (394) to This document registers a new COSE header parameter "receipts" (394)
enable Receipts to be conveyed in the protected and unprotected to enable Receipts to be conveyed in the protected and unprotected
headers of COSE Objects. headers of Enveloped COSE Structures.
When the receipts header parameter is present, the verifier MUST When the "receipts" header parameter is present, the verifier MUST
confirm that the associated Verifiable Data Structure and Verifiable confirm that the associated Verifiable Data Structure and Verifiable
Data Structure Proofs match entries present in the registries Data Structure Proofs match entries present in the registries
established in this specification, including values added in established in this specification, including values added in
subsequent registrations. subsequent registrations.
Receipts MUST be tagged as COSE_Sign1. Receipts MUST be tagged as COSE_Sign1.
The following definition from [RFC8610] is provided: The following definition from [RFC8610] is provided:
Signature_With_Receipt = #6.18(COSE_Sign1) Signature_With_Receipt = /6.18(COSE_Sign1)
cose.label = int / text cose-label = int / text
cose.values = any cose-values = any
Protected_Header = { Protected_Header = {
* cose.label => cose.values * cose-label => cose-values
} }
Unprotected_Header = { Unprotected_Header = {
&(receipts: 394) => [+ bstr .cbor Receipt] &(receipts: 394) => [+ bstr .cbor Receipt]
* cose.label => cose.values * cose-label => cose-values
} }
COSE_Sign1 = [ COSE_Sign1 = [
protected : bstr .cbor Protected_Header, protected : bstr .cbor Protected_Header,
unprotected : Unprotected_Header, unprotected : Unprotected_Header,
payload : bstr / nil, payload : bstr / nil,
signature : bstr signature : bstr
] ]
Receipt = Receipt_For_Inclusion / Receipt_For_Consistency Receipt = Receipt_For_Inclusion / Receipt_For_Consistency
; Note the proof formats shown here are for RFC9162_SHA256. ; Note the proof formats shown here are for RFC9162_SHA256.
; Other Verifiable Data Structures may have different proof formats. ; Other Verifiable Data Structures may have different proof formats.
Receipt_For_Inclusion = #6.18(Signed_Inclusion_Proof) Receipt_For_Inclusion = /6.18(Signed_Inclusion_Proof)
Signed_Inclusion_Proof = [ Signed_Inclusion_Proof = [
protected : bstr .cbor RFC9162_SHA256_Inclusion_Protected_Header protected : bstr .cbor RFC9162_SHA256_Inclusion_Protected_Header,
unprotected : RFC9162_SHA256_Inclusion_Unprotected_Header unprotected : RFC9162_SHA256_Inclusion_Unprotected_Header,
payload : bstr / nil payload : bstr / nil,
signature : bstr signature : bstr
] ]
RFC9162_SHA256_Inclusion_Protected_Header = { RFC9162_SHA256_Inclusion_Protected_Header = {
&(alg: 1) => int &(alg: 1) => int
&(vds: 395) => int &(vds: 395) => int
* cose.label => cose.values * cose-label => cose-values
} }
RFC9162_SHA256_Inclusion_Unprotected_Header = { RFC9162_SHA256_Inclusion_Unprotected_Header = {
&(vdp: 396) => RFC9162_SHA256_Verifiable_Inclusion_Proofs &(vdp: 396) => RFC9162_SHA256_Verifiable_Inclusion_Proofs
* cose.label => cose.values * cose-label => cose-values
} }
RFC9162_SHA256_Verifiable_Inclusion_Proofs = { RFC9162_SHA256_Verifiable_Inclusion_Proofs = {
&(inclusion-proof: -1) => RFC9162_SHA256_Inclusion_Proofs &(inclusion-proof: -1) => RFC9162_SHA256_Inclusion_Proofs
} }
RFC9162_SHA256_Inclusion_Proofs = [ + RFC9162_SHA256_Inclusion_Proof ] RFC9162_SHA256_Inclusion_Proofs = [ + RFC9162_SHA256_Inclusion_Proof ]
RFC9162_SHA256_Inclusion_Proof = bstr .cbor [ RFC9162_SHA256_Inclusion_Proof = bstr .cbor [
tree_size: uint, tree_size: uint,
leaf_index: uint, leaf_index: uint,
inclusion_path: [ + bstr ] inclusion_path: [ + bstr ]
] ]
Receipt_For_Consistency = #6.18(Signed_Consistency_Proof) Receipt_For_Consistency = /6.18(Signed_Consistency_Proof)
Signed_Consistency_Proof = [ Signed_Consistency_Proof = [
protected : bstr .cbor RFC9162_SHA256_Consistency_Protected_Header, protected : bstr .cbor RFC9162_SHA256_Consistency_Protected_Header,
unprotected : RFC9162_SHA256_Consistency_Unprotected_Header, unprotected : RFC9162_SHA256_Consistency_Unprotected_Header,
payload : bstr / nil, ; Newer Merkle tree root payload : bstr / nil, ; Newer Merkle Tree root
signature : bstr signature : bstr
] ]
RFC9162_SHA256_Consistency_Protected_Header = { RFC9162_SHA256_Consistency_Protected_Header = {
&(alg: 1) => int, &(alg: 1) => int,
&(vds: 395) => int, &(vds: 395) => int,
* cose.label => cose.values * cose-label => cose-values
} }
RFC9162_SHA256_Consistency_Unprotected_Header = { RFC9162_SHA256_Consistency_Unprotected_Header = {
&(vdp: 396) => RFC9162_SHA256_Verifiable_Consistency_Proofs &(vdp: 396) => RFC9162_SHA256_Verifiable_Consistency_Proofs
* cose.label => cose.values * cose-label => cose-values
} }
RFC9162_SHA256_Verifiable_Consistency_Proofs = { RFC9162_SHA256_Verifiable_Consistency_Proofs = {
&(consistency-proof: -2) => RFC9162_SHA256_Consistency_Proofs &(consistency-proof: -2) => RFC9162_SHA256_Consistency_Proofs
} }
RFC9162_SHA256_Consistency_Proofs = [ + RFC9162_SHA256_Consistency_Proof ] RFC9162_SHA256_Consistency_Proofs = [ + RFC9162_SHA256_Consistency_Proof ]
RFC9162_SHA256_Consistency_Proof = bstr .cbor [ RFC9162_SHA256_Consistency_Proof = bstr .cbor [
tree_size_1: uint, tree_size_1: uint,
tree_size_2: uint, tree_size_2: uint,
consistency_path: [ + bstr ] consistency_path: [ + bstr ]
] ]
Figure 1: CDDL for a COSE Sign1 with Attached Receipts Figure 1: CDDL for a COSE_Sign1 with Attached Receipts
The following informative EDN is provided: The following informative EDN is provided:
/ cose-sign1 / 18([ / cose-sign1 / 18([
/ protected / <<{ / protected / <<{
/ kid / 4 : h'bc297b51...e4edf0de', / kid / 4 : h'bc297b51...e4edf0de',
/ algorithm / 1 : -7, # ES256 / algorithm / 1 : -7, / ES256
}>>, }>>,
/ unprotected / { / unprotected / {
/ receipts / 394 : { / receipts / 394 : { [ << ... >> ]
<</ cose-sign1 / 18([ }
<</ cose-sign1 / 18([
/ protected / <<{ / protected / <<{
/ kid / 4 : h'abcdef12...34567890', / kid / 4 : h'abcdef12...34567890',
/ algorithm / 1 : -7, # ES256 / algorithm / 1 : -7, / ES256
/ vds / 395 : 1, # RFC9162 SHA-256 / vds / 395 : 1, / RFC9162 SHA-256
}>>, }>>,
/ unprotected / { / unprotected / {
/ proofs / 396 : { / proofs / 396 : {
/ inclusion / -1 : [ / inclusion / -1 : [
<<[ <<[
/ size / 9, / leaf / 8, / size / 9, / leaf / 8,
/ inclusion path / / inclusion path /
h'7558a95f...e02e35d6' h'7558a95f...e02e35d6'
]>> ]>>
], ],
}, },
}, },
/ payload / null, / payload / null,
/ signature / h'02d227ed...ccd3774f' / signature / h'02d227ed...ccd3774f'
])>>, ])>>,
<</ cose-sign1 / 18([ <</ cose-sign1 / 18([
/ protected / <<{ / protected / <<{
/ kid / 4 : h'abcdef12...34567890', / kid / 4 : h'abcdef12...34567890',
/ algorithm / 1 : -7, # ES256 / algorithm / 1 : -7, / ES256
/ vds / 395 : 1, # RFC9162 SHA-256 / vds / 395 : 1, / RFC9162 SHA-256
}>>, }>>,
/ unprotected / { / unprotected / {
/ proofs / 396 : { / proofs / 396 : {
/ inclusion / -1 : [ / inclusion / -1 : [
<<[ <<[
/ size / 6, / leaf / 5, / size / 6, / leaf / 5,
/ inclusion path / / inclusion path /
h'9352f974...4ffa7ce0', [ h'9352f974...4ffa7ce0',
h'54806f32...f007ea06' h'54806f32...f007ea06' ]
]>> ]>>
], ],
}, },
}, },
/ payload / null, / payload / null,
/ signature / h'36581f38...a5581960' / signature / h'36581f38...a5581960'
])>> ])>>
}, },
}, },
/ payload / h'0167c57c...deeed6d4', / payload / h'0167c57c...deeed6d4',
skipping to change at line 398 skipping to change at line 400
4.4. Profiles 4.4. Profiles
New Verifiable Data Structures can require the definition of a New Verifiable Data Structures can require the definition of a
profile. The payload in such definitions SHOULD be detached. profile. The payload in such definitions SHOULD be detached.
Detached payloads force verifiers to recompute the root from the Detached payloads force verifiers to recompute the root from the
proof and protect against implementation errors where the signature proof and protect against implementation errors where the signature
is verified but the payload is incompatible with the proof. Profiles is verified but the payload is incompatible with the proof. Profiles
of proof signatures that define additional protected header of proof signatures that define additional protected header
parameters are encouraged to make their presence mandatory to ensure parameters are encouraged to make their presence mandatory to ensure
that claims are processed with their intended semantics. One way to that claims are processed with their intended semantics. One way to
include this information in the COSE structure is use of the typ include this information in the COSE structure is use of the "typ"
(type) Header Parameter; see [RFC9596] and the similar guidance (type) header parameter; see [RFC9596] and the similar guidance
provided in [RFC9597]. provided in [RFC9597].
4.4.1. Registration Requirements 4.4.1. Registration Requirements
Each Verifiable Data Structure specification applying for inclusion Each Verifiable Data Structure specification applying for inclusion
in this registry MUST define how to encode the Verifiable Data in this registry MUST define how to encode the Verifiable Data
Structure identifier and its proof types in CBOR. Each specification Structure identifier and its Proof Types in CBOR. Each specification
MUST define how to produce and consume the supported proof types. MUST define how to produce and consume the supported Proof Types.
See Section 5 as an example. See Section 5 as an example.
Where a specification supports a choice of hash algorithm, a separate Where a specification supports a choice of hash algorithm, a separate
IANA registration must be made for each supported algorithm. For IANA registration must be made for each supported algorithm. For
example, to provide support for SHA256 and SHA3_256 with Merkle example, to provide support for SHA256 and SHA3_256 with Merkle
Inclusion Proofs and Merkle Consistency Proofs defined, respectively, inclusion proofs and Merkle consistency proofs defined, respectively,
in Section 2.1.3 of [RFC9162] and Section 2.1.4 of [RFC9162], both in Section 2.1.3 of [RFC9162] and Section 2.1.4 of [RFC9162], both
"RFC9162_SHA256" and "RFC9162_SHA3_256" require entries in the "RFC9162_SHA256" and "RFC9162_SHA3_256" require entries in the
relevant IANA registries. This document only defines relevant IANA registries. This document only defines
"RFC9162_SHA256". "RFC9162_SHA256".
5. RFC9162_SHA256 5. RFC9162_SHA256
This section defines how the data structure described in Section 2.1 This section defines how the data structure described in Section 2.1
of [RFC9162] is mapped to the terminology defined in this document, of [RFC9162] is mapped to the terminology defined in this document,
using [RFC8949] and [RFC9053]. using [RFC8949] and [RFC9053].
skipping to change at line 436 skipping to change at line 438
The integer identifier for this Verifiable Data Structure is 1. The The integer identifier for this Verifiable Data Structure is 1. The
string identifier for this Verifiable Data Structure is string identifier for this Verifiable Data Structure is
"RFC9162_SHA256", a Merkle Tree where SHA256 is used as the hash "RFC9162_SHA256", a Merkle Tree where SHA256 is used as the hash
algorithm (see Table 2). See Section 2.1.1 of [RFC9162] for a algorithm (see Table 2). See Section 2.1.1 of [RFC9162] for a
complete description of this Verifiable Data Structure. complete description of this Verifiable Data Structure.
5.2. Inclusion Proof 5.2. Inclusion Proof
See Section 2.1.3.1 of [RFC9162] for a complete description of this See Section 2.1.3.1 of [RFC9162] for a complete description of this
Verifiable Data Structure Proof type. Verifiable Data Structure Proof Type.
The CBOR representation of an inclusion proof for RFC9162_SHA256 is: The CBOR representation of an inclusion proof for RFC9162_SHA256 is:
inclusion-proof = bstr .cbor [ inclusion-proof = bstr .cbor [
; tree size at current Merkle root ; tree size at current Merkle Tree root
tree-size: uint tree-size: uint
; index of leaf in tree ; index of leaf in tree
leaf-index: uint leaf-index: uint
; path from leaf to current Merkle root ; path from leaf to current Merkle Tree root
inclusion-path: [ + bstr ] inclusion-path: [ + bstr ]
] ]
Figure 3: CBOR-Encoded Inclusion Proof for RFC9162_SHA256 Figure 3: CBOR-Encoded Inclusion Proof for RFC9162_SHA256
The term leaf-index is used for alignment with the use established in The term leaf-index is used for alignment with the use established in
Section 2.1.3.2 of [RFC9162]. Section 2.1.3.2 of [RFC9162].
Note that [RFC9162] defines inclusion proofs only for leaf nodes, and Note that [RFC9162] defines inclusion proofs only for leaf nodes, and
that: that:
| If leaf_index is greater than or equal to tree_size, then fail the | If leaf_index is greater than or equal to tree_size, then fail the
| proof verification. | proof verification.
The identifying index of a leaf node is relative to all nodes in the The identifying index of a leaf node is relative to all nodes in the
tree size for which the proof was obtained. tree size for which the proof was obtained.
5.2.1. Receipt of Inclusion 5.2.1. Receipt of Inclusion
In a signed inclusion proof, the payload is the Merkle tree root that In a signed proof, the payload is the Merkle Tree root that
corresponds to the log at size tree-size. The protected header for corresponds to the log at size tree-size. The protected header for
an RFC9162_SHA256 inclusion proof signature is: an RFC9162_SHA256 inclusion proof signature is:
protected-header-map = { protected-header-map = {
&(alg: 1) => int &(alg: 1) => int
&(vds: 395) => int &(vds: 395) => int
* cose-label => cose-value * cose-label => cose-value
} }
Figure 4: Protected Header for a Receipt of Inclusion Figure 4: Protected Header for a Receipt of Inclusion
skipping to change at line 509 skipping to change at line 511
Figure 5: A Verifiable Data Structure Proofs in an Unprotected Header Figure 5: A Verifiable Data Structure Proofs in an Unprotected Header
vdp (label: 396): REQUIRED. Verifiable Data Structure Proofs. vdp (label: 396): REQUIRED. Verifiable Data Structure Proofs.
Value type: Map. Value type: Map.
inclusion-proof (label: -1): REQUIRED. Inclusion proofs. Value inclusion-proof (label: -1): REQUIRED. Inclusion proofs. Value
type: Array of bstr. type: Array of bstr.
The payload of an RFC9162_SHA256 inclusion proof signature is the The payload of an RFC9162_SHA256 inclusion proof signature is the
Merkle tree hash as defined in [RFC9162]. Merkle Tree hash as defined in [RFC9162].
An EDN example for a Receipt containing an inclusion proof for An EDN example for a Receipt containing an inclusion proof for
RFC9162_SHA256 with a detached payload (see Section 4.4) is: RFC9162_SHA256 with a detached payload (see Section 4.4) is:
/ cose-sign1 / 18([ / cose-sign1 / 18([
/ protected / <<{ / protected / <<{
/ algorithm / 1 : -7, # ES256 / algorithm / 1 : -7, / ES256
/ vds / 395 : 1, # RFC9162 SHA-256 / vds / 395 : 1, / RFC9162 SHA-256
}>>, }>>,
/ unprotected / { / unprotected / {
/ proofs / 396 : { / proofs / 396 : {
/ inclusion / -1 : [ / inclusion / -1 : [
<<[ <<[
/ size / 20, / leaf / 17, / size / 20, / leaf / 17,
/ inclusion path / / inclusion path /
h'fc9f050f...221c92cb', [ h'fc9f050f...221c92cb',
h'bd0136ad...6b28cf21', h'bd0136ad...6b28cf21',
h'd68af9d6...93b1632b' h'd68af9d6...93b1632b' ]
]>> ]>>
], ],
}, },
}, },
/ payload / null, / payload / null,
/ signature / h'de24f0cc...9a5ade89' / signature / h'de24f0cc...9a5ade89'
]) ])
Figure 6: Receipt of Inclusion Figure 6: Receipt of Inclusion
The VDS in the protected header is necessary to understand the The VDS in the protected header is necessary to understand the
inclusion proof structure in the unprotected header. inclusion proof structure in the unprotected header.
The inclusion proof and signature are verified in order. First, the The inclusion proof and signature are verified in order. First, the
verifier applies the inclusion proof to a possible entry (set member) verifier applies the inclusion proof to a possible entry (set member)
bytes. If this process fails, the inclusion proof may have been bytes. If this process fails, the inclusion proof may have been
tampered with. If this process succeeds, the result is a Merkle tampered with. If this process succeeds, the result is a Merkle Tree
root, which in the attached as the COSE Sign1 payload. Second, the root, which in the attached as the COSE_Sign1 payload. Second, the
verifier checks the signature of the COSE Sign1. If the resulting verifier checks the signature of the COSE_Sign1. If the resulting
signature can be verified, the Receipt has proved inclusion of the signature can be verified, the Receipt has proved inclusion of the
entry in the Verifiable Data Structure. If the resulting signature entry in the Verifiable Data Structure. If the resulting signature
cannot be verified, the signature may have been tampered with. cannot be verified, the signature may have been tampered with.
5.3. Consistency Proof 5.3. Consistency Proof
See Section 2.1.4.1 of [RFC9162] for a complete description of this See Section 2.1.4.1 of [RFC9162] for a complete description of this
Verifiable Data Structure Proof type. Verifiable Data Structure Proof Type.
The cbor representation of a consistency proof for RFC9162_SHA256 is: The cbor representation of a consistency proof for RFC9162_SHA256 is:
consistency-proof = bstr .cbor [ consistency-proof = bstr .cbor [
; older Merkle root tree size ; older Merkle Tree size
tree-size-1: uint tree-size-1: uint
; newer Merkle root tree size ; newer Merkle Tree size
tree-size-2: uint tree-size-2: uint
; path from older Merkle root to newer Merkle root. ; path from older Merkle Tree to newer Merkle Tree
consistency-path: [ + bstr ] consistency-path: [ + bstr ]
] ]
Figure 7: CBOR-Encoded Consistency Proof for RFC9162_SHA256 Figure 7: CBOR-Encoded Consistency Proof for RFC9162_SHA256
5.3.1. Receipt of Consistency 5.3.1. Receipt of Consistency
In a signed consistency proof, the newer Merkle tree root (proven to In a signed consistency proof, the newer Merkle Tree root (proven to
be consistent with an older Merkle tree root), is an attached payload be consistent with an older Merkle Tree root) is a detached payload
and corresponds to the log at size tree-size-2. and corresponds to the log at size tree-size-2.
The protected header for an RFC9162_SHA256 consistency proof The protected header for an RFC9162_SHA256 consistency proof
signature is: signature is:
protected-header-map = { protected-header-map = {
&(alg: 1) => int &(alg: 1) => int
&(vds: 395) => int &(vds: 395) => int
* cose-label => cose-value * cose-label => cose-value
} }
skipping to change at line 617 skipping to change at line 619
* cose-label => cose-value * cose-label => cose-value
} }
vdp (label: 396): REQUIRED. Verifiable Data Structure Proofs. vdp (label: 396): REQUIRED. Verifiable Data Structure Proofs.
Value type: Map. Value type: Map.
consistency-proof (label: -2): REQUIRED. Consistency proofs. Value consistency-proof (label: -2): REQUIRED. Consistency proofs. Value
type: Array of bstr. type: Array of bstr.
The payload of an RFC9162_SHA256 consistency proof signature is: The The payload of an RFC9162_SHA256 consistency proof signature is: The
newer Merkle tree hash as defined in [RFC9162]. newer Merkle Tree hash as defined in [RFC9162].
An EDN example for a Receipt containing a consistency proof for An EDN example for a Receipt containing a consistency proof for
RFC9162_SHA256 with a detached payload (see Section 4.4) is: RFC9162_SHA256 with a detached payload (see Section 4.4) is:
/ cose-sign1 / 18([ / cose-sign1 / 18([
/ protected / <<{ / protected / <<{
/ algorithm / 1 : -7, # ES256 / algorithm / 1 : -7, / ES256
/ vds / 395 : 1, # RFC9162 SHA-256 / vds / 395 : 1, / RFC9162 SHA-256
}>>, }>>,
/ unprotected / { / unprotected / {
/ proofs / 396 : { / proofs / 396 : {
/ consistency / -2 : [ / consistency / -2 : [
<<[ <<[
/ old / 20, / new / 104, / old / 20, / new / 104,
/ consistency path / / consistency path /
h'e5b3e764...c4a813bc', h'e5b3e764...c4a813bc',
h'87e8a084...4f529f69', h'87e8a084...4f529f69',
h'f712f76d...92a0ff36', h'f712f76d...92a0ff36',
skipping to change at line 654 skipping to change at line 656
/ signature / h'94469f73...52de67a1' / signature / h'94469f73...52de67a1'
]) ])
Figure 9: Example Consistency Receipt Figure 9: Example Consistency Receipt
The VDS in the protected header is necessary to understand the The VDS in the protected header is necessary to understand the
consistency proof structure in the unprotected header. consistency proof structure in the unprotected header.
The signature and consistency proof are verified in order. The signature and consistency proof are verified in order.
First, the verifier checks the signature on the COSE Sign1. If the First, the verifier checks the signature on the COSE_Sign1. If the
verification fails, the consistency proof is not checked. Second, verification fails, the consistency proof is not checked. Second,
the consistency proof is checked by applying a previous inclusion the consistency proof is checked by applying a previous inclusion
proof to the consistency proof. If the verification fails, the proof to the consistency proof. If the verification fails, the
append only property of the Verifiable Data Structure is not assured. append-only property of the Verifiable Data Structure is not assured.
This approach is specific to RFC9162_SHA256; different Verifiable This approach is specific to RFC9162_SHA256; different Verifiable
Data Structures may not support consistency proofs. It is Data Structures may not support consistency proofs. It is
recommended that implementations return a single boolean result for recommended that implementations return a single boolean result for
Receipt-verification operations to reduce the chance of accepting a Receipt-verification operations to reduce the chance of accepting a
valid signature over an invalid consistency proof. valid signature over an invalid consistency proof.
6. Privacy Considerations 6. Privacy Considerations
The privacy considerations section of [RFC9162] and [RFC9053] apply The privacy considerations section of [RFC9162] and [RFC9053] apply
to this document. to this document.
skipping to change at line 791 skipping to change at line 793
* Point squatting should be discouraged. Reviewers are encouraged * Point squatting should be discouraged. Reviewers are encouraged
to get sufficient information for registration requests to ensure to get sufficient information for registration requests to ensure
that the usage is not going to duplicate one that is already that the usage is not going to duplicate one that is already
registered and that the point is likely to be used in deployments. registered and that the point is likely to be used in deployments.
* Specifications are required for all point assignments. early * Specifications are required for all point assignments. early
allocation is permissible, see Section 2 of [RFC7120]. allocation is permissible, see Section 2 of [RFC7120].
* It is not permissible to assign points in COSE Verifiable Data * It is not permissible to assign points in COSE Verifiable Data
Structure Algorithms for which no corresponding COSE Verifiable Structure algorithms for which no corresponding COSE Verifiable
Data Structure Proofs entry exists, and vice versa. Data Structure Proofs entry exists, and vice versa.
* The change controller for related registrations of structures and * The change controller for related registrations of structures and
proofs should be the same. proofs should be the same.
8.2.2. Templates and Initial Contents 8.2.2. Templates and Initial Contents
8.2.2.1. COSE Verifiable Data Structure Algorithms Registry 8.2.2.1. COSE Verifiable Data Structure Algorithms Registry
Registration Template: Registration Template:
skipping to change at line 845 skipping to change at line 847
Registry Contents Registry Contents
8.2.2.2. COSE Verifiable Data Structure Proofs Registry 8.2.2.2. COSE Verifiable Data Structure Proofs Registry
Registration Template: Registration Template:
Verifiable Data Structure: Verifiable Data Structure:
This value used identifies the related Verifiable Data This value used identifies the related Verifiable Data
Structure. Structure.
Name: Name:
This is a descriptive name for the proof type that enables This is a descriptive name for the Proof Type that enables
easier reference to the item. easier reference to the item.
Label: Label:
This is the value used to identify the Verifiable Data This is the value used to identify the Verifiable Data
Structure Proof type. Structure Proof Type.
CBOR Type: CBOR Type:
This contains the CBOR type for the value portion of the label. This contains the CBOR type for the value portion of the label.
Description: Description:
This field contains a brief description of the proof type. This field contains a brief description of the Proof Type.
Reference: Reference:
This contains a pointer to the public specification for the This contains a pointer to the public specification for the
proof type. Proof Type.
Change Controller: Change Controller:
For Standards Track RFCs, list the "IETF". For others, give For Standards Track RFCs, list the "IETF". For others, give
the name of the responsible party. Other details (e.g., postal the name of the responsible party. Other details (e.g., postal
address, email address, home page URI) may also be included. address, email address, home page URI) may also be included.
+==========+===========+=====+=====+===========+==========+=========+ +==========+===========+=====+=====+===========+==========+=========+
|Verifiable|Name |Label|CBOR |Description|Change |Reference| |Verifiable|Name |Label|CBOR |Description|Change |Reference|
|Data | | |Type | |Controller| | |Data | | |Type | |Controller| |
|Structure | | | | | | | |Structure | | | | | | |
+==========+===========+=====+=====+===========+==========+=========+ +==========+===========+=====+=====+===========+==========+=========+
|1 |inclusion |-1 |array|Proof of |IETF |RFC 9942,| |1 |inclusion |-1 |array|Proof of |IETF |RFC 9942,|
| |proofs | |(of |inclusion | |Section | | |proofs | |(of |inclusion | |Section |
| | | |bstr)| | |5.2 | | | | |bstr)| | |5.2 |
+----------+-----------+-----+-----+-----------+----------+---------+ +----------+-----------+-----+-----+-----------+----------+---------+
|1 |consistency|-2 |array|Proof of |IETF |RFC 9942,| |1 |consistency|-2 |array|Proof of |IETF |RFC 9942,|
| |proofs | |(of |append only| |Section | | |proofs | |(of |append-only| |Section |
| | | |bstr)|property | |5.3 | | | | |bstr)|property | |5.3 |
+----------+-----------+-----+-----+-----------+----------+---------+ +----------+-----------+-----+-----+-----------+----------+---------+
Table 3: COSE Verifiable Data Structure Proofs Initial Registry Table 3: COSE Verifiable Data Structure Proofs Initial Registry
Contents Contents
9. References 9. References
9.1. Normative References 9.1. Normative References
skipping to change at line 933 skipping to change at line 935
<https://www.rfc-editor.org/info/rfc9596>. <https://www.rfc-editor.org/info/rfc9596>.
[RFC9597] Looker, T. and M.B. Jones, "CBOR Web Token (CWT) Claims in [RFC9597] Looker, T. and M.B. Jones, "CBOR Web Token (CWT) Claims in
COSE Headers", RFC 9597, DOI 10.17487/RFC9597, June 2024, COSE Headers", RFC 9597, DOI 10.17487/RFC9597, June 2024,
<https://www.rfc-editor.org/info/rfc9597>. <https://www.rfc-editor.org/info/rfc9597>.
9.2. Informative References 9.2. Informative References
[CBOR-EDN] Bormann, C., "CBOR Extended Diagnostic Notation (EDN)", [CBOR-EDN] Bormann, C., "CBOR Extended Diagnostic Notation (EDN)",
Work in Progress, Internet-Draft, draft-ietf-cbor-edn- Work in Progress, Internet-Draft, draft-ietf-cbor-edn-
literals-20, 2 March 2026, literals-21, 30 March 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-cbor- <https://datatracker.ietf.org/doc/html/draft-ietf-cbor-
edn-literals-20>. edn-literals-21>.
[RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code
Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
2014, <https://www.rfc-editor.org/info/rfc7120>. 2014, <https://www.rfc-editor.org/info/rfc7120>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
skipping to change at line 1004 skipping to change at line 1006
Rheinstrasse 75 Rheinstrasse 75
64295 Darmstadt 64295 Darmstadt
Germany Germany
Email: henk.birkholz@ietf.contact Email: henk.birkholz@ietf.contact
Antoine Delignat-Lavaud Antoine Delignat-Lavaud
Microsoft Microsoft
United Kingdom United Kingdom
Email: antdl@microsoft.com Email: antdl@microsoft.com
Cedric Fournet Cédric Fournet
Microsoft Microsoft
United Kingdom United Kingdom
Email: fournet@microsoft.com Email: fournet@microsoft.com
 End of changes. 63 change blocks. 
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