]> MATTR

tobias.looker@mattr.global

paul.bastian@posteo.de

Robert Bosch GmbH

christiancarl.bormann@bosch.com

This specification defines status list data structures and processing rules for representing the status of tokens secured by JSON Object Signing and Encryption (JOSE) or CBOR Object Signing and Encryption(COSE), such as JSON Web Tokens (JWTs), CBOR Web Tokens (CWTs) and ISO mdoc. The status list token data structures themselves are also represented as JWTs or CWTs. About This Document The latest revision of this draft can be found at . Status information for this document may be found at . Source for this draft and an issue tracker can be found at .

Introduction Token formats secured by JOSE or COSE , such as JSON Web Tokens (JWTs) , CBOR Web Tokens (CWTs) and ISO mdoc , have vast possible applications. Some of these applications can involve issuing a token whereby certain semantics about the token can change over time, which are important to be able to communicate to relying parties in an interoperable manner, such as whether the token is considered invalidated or suspended by its issuer. This document defines a Status List and its representations in JSON and CBOR formats that describe the individual statuses of multiple Referenced Tokens, which themselves are JWTs or CWTs. The statuses of all Referenced Tokens are conveyed via a bit array in the Status List. Each Referenced Token is allocated an index during issuance that represents its position within this bit array. The value of the bit(s) at this index correspond to the Referenced Token's status. A Status List may either be provided via HTTPS or be signed and embedded into a Status List Token, whereas this document defines its representations in JWT and CWT. Status Lists may be composed for expressing a range of Status Types. This document defines basic Status Types for the most common use cases as well as an extensibility mechanism for custom Status Types. The document also defines how an issuer of a Referenced Token references a Status List (Token). An example for the usage of a Status List is to manage the status of issued access tokens as defined in section 1.4 of . Token Introspection defines another way to determine the status of an issued access token, but it requires the party trying to validate an access tokens status to directly contact the token issuer, whereas the mechanism defined in this specification does not have this limitation. Another possible use case for the Status List is to express the status of verifiable credentials (Referenced Tokens) issued by an Issuer in the Issuer-Holder-Verifier model . The following diagram depicts the basic conceptual relationship. | Referenced Token | | (JSON or CBOR) <------------------+ (JOSE, COSE) | | | references | | +-------+-----------+ +--------+---------------+ | |embedded in v +-------------------+ | | | Status List Token | | (JWT or CWT) | | | +-------------------+ ]]>

Rationale Revocation mechanisms are an essential part for most identity ecosystems. In the past, revocation of X.509 TLS certificates has been proven difficult. Traditional certificate revocation lists (CRLs) have limited scalability; Online Certificate Status Protocol (OCSP) has additional privacy risks, since the client is leaking the requested website to a third party. OCSP stapling is addressing some of these problems at the cost of less up-to-date data. Modern approaches use accumulator-based revocation registries and Zero-Knowledge-Proofs to accommodate for this privacy gap, but face scalability issues again. This specification seeks to find a balance between scalability, security, and privacy by minimizing the status information to mere bits (often a single bit) and compressing the resulting binary data. Thereby, a Status List may contain statuses of many thousands or millions Referenced Tokens while remaining as small as possible. Placing large amounts of Referenced Tokens into the same list also enables herd privacy relative to the Issuer. This specification establishes the IANA "Status Mechanism Methods" registry for status mechanism and registers the members defined by this specification. Other specifications can register other members used for status retrieval.

Design Considerations The decisions taken in this specification aim to achieve the following design goals:

• the specification shall favor a simple and easy to understand concept
• the specification shall be easy, fast and secure to implement in all major programming languages
• the specification shall be optimized to support the most common use cases and avoid unnecessary complexity of corner cases
• the Status List shall scale up to millions of tokens to support large scale government or enterprise use cases
• the Status List shall enable caching policies and offline support
• the specification shall support JSON and CBOR based tokens
• the specification shall not specify key resolution or trust frameworks
• the specification shall design an extension point to convey information about the status of a token that can be re-used by other mechanisms

Conventions and Definitions 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 when, and only when, they appear in all capitals, as shown here.

Terminology

Issuer:

An entity that issues the Referenced Token and provides the status information of the Referenced Token by serving a Status List Token on a public endpoint.

Relying Party:

An entity that relies on the Status List to validate the status of the Referenced Token. Also known as Verifier.

Status List:

An object in JSON or CBOR representation containing a bit array that lists the statuses of many Referenced Tokens.

Status List Token:

A token in JWT or CWT representation that contains a cryptographically secured Status List.

Referenced Token:

A cryptographically secured data structure which contains a reference to a Status List or Status List Token. It is RECOMMENDED to use JSON or CBOR for representation of the token and secure it using JSON Object Signing as defined in or CBOR Object Signing and Encryption as defined in . The information from the contained Status List may give a Relying Party additional information about up-to-date status of the Referenced Token.

base64url:

Denotes the URL-safe base64 encoding without padding as defined in Section 2 of as "Base64url Encoding".

Status List A Status List is a byte array that contains the statuses of many Referenced Tokens represented by one or multiple bits. A common representation of a Status List is composed by the following algorithm:

1. Each status of a Referenced Token MUST be represented with a bit-size of 1,2,4, or 8. Therefore up to 2,4,16, or 256 statuses for a Referenced Token are possible, depending on the bit-size. This limitation is intended to limit bit manipulation necessary to a single byte for every operation and thus keeping implementations simpler and less error prone.
2. The overall Status List is encoded as a byte array. Depending on the bit-size, each byte corresponds to 8/(#bit-size) statuses (8,4,2, or 1). The status of each Referenced Token is identified using the index that maps to one or more specific bits within the byte array. The index starts counting at 0 and ends with "size" - 1 (being the last valid entry). The bits within an array are counted from least significant bit "0" to the most significant bit ("7"). All bits of the byte array at a particular index are set to a status value.
3. The byte array is compressed using DEFLATE with the ZLIB data format. Implementations are RECOMMENDED to use the highest compression level available.

The following example illustrates a Status List that represents the statuses of 16 Referenced Tokens, requiring 16 bits (2 bytes) for the uncompressed byte array: These bits are concatenated:

Status List in JSON Format This section defines the structure for a JSON-encoded Status List:

• status_list: REQUIRED. JSON Object that contains a Status List. It MUST contain at least the following claims:
  • bits: REQUIRED. JSON Integer specifying the number of bits per Referenced Token in the Status List (lst). The allowed values for bits are 1,2,4 and 8.
  • lst: REQUIRED. JSON String that contains the status values for all the Referenced Tokens it conveys statuses for. The value MUST be the base64url-encoded Status List as specified in .
  • aggregation_uri: OPTIONAL. JSON String that contains a URI to retrieve the Status List Aggregation for this type of Referenced Token. See section for further detail.

The following example illustrates the JSON representation of the Status List:

Status List in CBOR Format This section defines the structure for a CBOR-encoded Status List:

• The StatusList structure is a map (Major Type 5) and defines the following entries:
  • bits: REQUIRED. Unsigned int (Major Type 0) that contains the number of bits per Referenced Token in the Status List. The allowed values for bits are 1, 2, 4 and 8.
  • lst: REQUIRED. Byte string (Major Type 2) that contains the Status List as specified in .
  • aggregation_uri: OPTIONAL. Text string (Major Type 3) that contains a URI to retrieve the Status List Aggregation for this type of Referenced Token. See section for further detail.

The following example illustrates the CBOR representation of the Status List in Hex: The following is the CBOR Annotated Hex output of the example above:

Status List Token A Status List Token embeds the Status List into a token that is cryptographically signed and protects the integrity of the Status List. This allows for the Status List Token to be hosted by third parties or be transferred for offline use cases. This section specifies Status List Tokens in JSON Web Token (JWT) and CBOR Web Token (CWT) format.

Status List Token in JWT Format The Status List Token MUST be encoded as a "JSON Web Token (JWT)" according to . The following content applies to the JWT Header:

• typ: REQUIRED. The JWT type MUST be statuslist+jwt.

The following content applies to the JWT Claims Set:

• sub: REQUIRED. The sub (subject) claim MUST specify the URI of the Status List Token. The value MUST be equal to that of the uri claim contained in the status_list claim of the Referenced Token.
• iat: REQUIRED. The iat (issued at) claim MUST specify the time at which the Status List Token was issued.
• exp: OPTIONAL. The exp (expiration time) claim, if present, MUST specify the time at which the Status List Token is considered expired by its issuer.
• ttl: OPTIONAL. The ttl (time to live) claim, if present, MUST specify the maximum amount of time, in seconds, that the Status List Token can be cached by a consumer before a fresh copy SHOULD be retrieved. The value of the claim MUST be a positive number.
• status_list: REQUIRED. The status_list (status list) claim MUST specify the Status List conforming to the rules outlined in .

The following additional rules apply:

1. The JWT MAY contain other claims.
2. The JWT MUST be digitally signed using an asymmetric cryptographic algorithm. Relying parties MUST reject the JWT if it is using a Message Authentication Code (MAC) algorithm. Relying parties MUST reject JWTs with an invalid signature.
3. Relying parties MUST reject JWTs that are not valid in all other respects per "JSON Web Token (JWT)" .
4. Application of additional restrictions and policy are at the discretion of the verifying party.

The following is a non-normative example for a Status List Token in JWT format:

Status List Token in CWT Format The Status List Token MUST be encoded as a "CBOR Web Token (CWT)" according to . The following content applies to the CWT protected header:

• 16 (type): REQUIRED. The type of the CWT MUST be statuslist+cwt as defined in .

The following content applies to the CWT Claims Set:

• 2 (subject): REQUIRED. Same definition as sub claim in .
• 6 (issued at): REQUIRED. Same definition as iat claim in .
• 4 (expiration time): OPTIONAL. Same definition as exp claim in .
• 65534 (time to live): OPTIONAL. Same definition as ttl claim in .
• 65533 (status list): REQUIRED. The status list claim MUST specify the Status List conforming to the rules outlined in .

The following additional rules apply:

1. The CWT MAY contain other claims.
2. The CWT MUST be digitally signed using an asymmetric cryptographic algorithm. Relying parties MUST reject the CWT if it is using a Message Authentication Code (MAC) algorithm. Relying parties MUST reject CWTs with an invalid signature.
3. Relying parties MUST reject CWTs that are not valid in all other respects per "CBOR Web Token (CWT)" .
4. Application of additional restrictions and policy are at the discretion of the verifying party.

The following is a non-normative example for a Status List Token in CWT format in Hex: The following is the CBOR Annotated Hex output of the example above:

Referenced Token

Status Claim By including a "status" claim in a Referenced Token, the Issuer is referencing a mechanism to retrieve status information about this Referenced Token. The claim contains members used to reference to a status list as defined in this specification. Other members of the "status" object may be defined by other specifications. This is analogous to "cnf" claim in Section 3.1 of in which different authenticity confirmation methods can be included.

Referenced Token in JOSE The Referenced Token MAY be encoded as a "JSON Web Token (JWT)" according to or other formats based on JOSE. The following content applies to the JWT Claims Set:

• status: REQUIRED. The status (status) claim MUST specify a JSON Object that contains at least one reference to a status mechanism.
  • status_list: REQUIRED when the status list mechanism defined in this specification is used. It contains a reference to a Status List or Status List Token. It MUST at least contain the following claims:
    • idx: REQUIRED. The idx (index) claim MUST specify an Integer that represents the index to check for status information in the Status List for the current Referenced Token. The value of idx MUST be a non-negative number, containing a value of zero or greater.
    • uri: REQUIRED. The uri (URI) claim MUST specify a String value that identifies the Status List or Status List Token containing the status information for the Referenced Token. The value of uri MUST be a URI conforming to .

Application of additional restrictions and policy are at the discretion of the verifying party. The following is a non-normative example for a decoded header and payload of a Referenced Token: SD-JWT-based Verifiable Credentials introduce the usage of Status List in Section 3.2.2.2. The "status" object uses the same encoding as a JWT as defined in . The following is a non-normative example for a Referenced Token in SD-JWT-VC serialized form as received from an Issuer: Resulting payload of the example above:

Referenced Token in COSE The Referenced Token MAY be encoded as a "COSE Web Token (CWT)" object according to or other formats based on COSE. The following content applies to the CWT Claims Set:

• 65535 (status): REQUIRED. The status claim is encoded as a Status CBOR structure and MUST include at least one data item that refers to a status mechanism. Each data item in the Status CBOR structure comprises a key-value pair, where the key must be a CBOR text string (Major Type 3) specifying the identifier of the status mechanism, and the corresponding value defines its contents. This specification defines the following data items:
  • status_list (status list): REQUIRED when the status list mechanism defined in this specification is used. It has the same definition as the status_list claim in but MUST be encoded as a StatusListInfo CBOR structure with the following fields:
    • idx: REQUIRED. Same definition as idx claim in .
    • uri: REQUIRED. Same definition as uri claim in .

Application of additional restrictions and policy are at the discretion of the verifying party. The following is a non-normative example of a Referenced Token in CWT format in Hex: The following is the CBOR Annotated Hex output of the example above: ISO mdoc may utilize the Status List mechanism by introducing the status parameter in the Mobile Security Object (MSO) as specified in Section 9.1.2. The status parameter uses the same encoding as a CWT as defined in . It is RECOMMENDED to use status for the label of the field that contains the Status CBOR structure. Application of additional restrictions and policy are at the discretion of the verifying party. The following is a non-normative example for an IssuerAuth as specified in ISO mDL (also referred to as signed MSO) in Hex: The following is the CBOR Diagnostic Notation of the example above: >, { 33: h'308201ef30820195a00302010202140bfec7da97e048e15ac3dacb9ea fe82e64fd07f5300a06082a8648ce3d04030230233114301206035504030c0b 75746f7069612069616361310b3009060355040613025553301e170d3234313 030313030303030305a170d3235313030313030303030305a30213112301006 035504030c0975746f706961206473310b30090603550406130255533059301 306072a8648ce3d020106082a8648ce3d03010703420004ace7ab7340e5d964 8c5a72a9a6f56745c7aad436a03a43efea77b5fa7b88f0197d57d8983e1b37d 3a539f4d588365e38cbbf5b94d68c547b5bc8731dcd2f146ba381a83081a530 1c0603551d1f041530133011a00fa00d820b6578616d706c652e636f6d301e0 603551d120417301581136578616d706c65406578616d706c652e636f6d301d 0603551d0e0416041414e29017a6c35621ffc7a686b7b72db06cd12351301f0 603551d2304183016801454fa2383a04c28e0d930792261c80c4881d2c00b30 0e0603551d0f0101ff04040302078030150603551d250101ff040b300906072 8818c5d050102300a06082a8648ce3d0403020348003045022100b7103fd4b9 0529f50bd6f70c5ae5ce7f4f3d4d15a4e082812f9fa1f5c2e5aa0a0220070b2 822ec7ce6c56804923a85b2cfbffd054cf9a915f070cfef7179a4bc6569' }, << 24( << { "status": { "status_list": { "idx": 412, "uri": "https://example.com/statuslists/1" } }, "docType": "org.iso.18013.5.1.mDL", "version": "1.0", "validityInfo": { "signed": 2024-10-01 13:30:02+00:00, "validFrom": 2024-10-01 13:30:02+00:00, "validUntil": 2025-10-01 13:30:02+00:00 }, "valueDigests": { "org.iso.18013.5.1": { 0: h'a81d65ed5075fbd7ee19fa66e2bb3047ed826e2769873e7ef07c92 3da7a6f243', 1: h'48701a9546492284d266ed81d439230a582d0e1f17a08ab1859a3e fe980690a4', 2: h'd11fe48c8835b30bfb3895c3905436ddfb63f59ab9eee181b11098 53292a8f62', 3: h'a741bf05e20a8bc359e32426106ed0899b2c60262cc3acc637ddc9 941095fb7a', 4: h'ab67cb9a8f20a8572f77f02727367d08dc8e57fb89deb46b9c626e 94457b7d8b', 5: h'bacddb4142b3842bd555206eb5acb27ded063294995c7e7fefbf93 ece522604d', 6: h'bfd02b3aebdc05b53b5539226c38088d6d784b0ea0fab69eb93116 50a48d3253', 7: h'27dab70fe71da63e5e5d199e8ae5b79cbe8904bc30c5b7544fb809 e02ccb3e6a', 8: h'0dbd7ccc9c7727d3d17295f1b6f1914071670ee23d4d33530c31f1 f406b8e3b7', 9: h'a5beb5efadf37f21637209abc519830681cc51f334818a823fec13 b29552f5ba', 10: h'd8047c95f9272d7d07b2c13a9f5ac2ee02380ab272a165e569391 d89a2152c3c', 11: h'04939930ffb4911ef03487a153605a30368b69f2437d6d21b4c90 f92bc144c3e' } }, "deviceKeyInfo": { "deviceKey": { 1: 2, -1: 1, -2: h'96313d6c63e24e3372742bfdb1a33ba2c897dcd68ab8c753e4fbd 48dca6b7f9a', -3: h'1fb3269edd418857de1b39a4e4a44b92fa484caa722c228288f01 d0c03a2c3d6' } }, "digestAlgorithm": "SHA-256" } >> ) >>, h'b7c2d4abe85aa5ba814ef95de0385c71c802be8ac33a4a971a85ed800ba7acb 59cb21035f4a68fc0caa450cbefd3b255aec72f83595f0ae7b7d50fe8a1c4cafe' ] ]]>

Status Types This document defines potential statuses of Referenced Tokens as Status Type values. If the Status List contains more than one bit per token (as defined by "bits" in the Status List), then the whole value of bits MUST describe one value. A Status List can not represent multiple statuses per Referenced Token. The registry in this document describes the basic Status Type values required for the most common use cases. Additional values may defined for particular use cases.

Status Types Values A status describes the state, mode, condition or stage of an entity that is described by the Status List. Status Types MUST be numeric values between 0 and 255. Status types described by this specification comprise:

• 0x00 - "VALID" - The status of the Token is valid, correct or legal.
• 0x01 - "INVALID" - The status of the Token is revoked, annulled, taken back, recalled or cancelled. This state is irreversible.
• 0x02 - "SUSPENDED" - The status of the Token is temporarily invalid, hanging, debarred from privilege. This state is reversible.

The issuer of the Status List MUST choose an adequate bits (bit size) to be able to describe the required Status Types for the application. The processing rules for JWT or CWT precede any evaluation of a Referenced Token's status. For example, if a token is evaluated as being expired through the "exp" (Expiration Time) but also has a status of 0x00 ("VALID"), the token is considered expired.

Verification and Processing

Status List Request To obtain the Status List or Status List Token, the Relying Party MUST send an HTTP GET request to the URI provided in the Referenced Token. If the Status List is provided by an HTTP endpoint (and not as a Status List Token), the provider of the Status List MUST utilize TLS. Which version(s) should be implemented will vary over time. A TLS server certificate check MUST be performed as defined in Section 5 and 6 of . The HTTP endpoint SHOULD support the use of Cross-Origin Resource Sharing (CORS) and/or other methods as appropriate to enable Browser-Based clients to access it. The Relying Party SHOULD send the following Accept-Header to indicate the requested response type:

• "application/statuslist+json" for Status List in JSON format
• "application/statuslist+jwt" for Status List in JWT format
• "application/statuslist+cbor" for Status List in CBOR format
• "application/statuslist+cwt" for Status List in CWT format

If the Relying Party does not send an Accept Header, the response type is assumed to be known implicit or out-of-band.

Status List Response In the successful response, the Status List Provider MUST use the following content-type:

• "application/statuslist+json" for Status List in JSON format
• "application/statuslist+jwt" for Status List in JWT format
• "application/statuslist+cbor" for Status List in CBOR format
• "application/statuslist+cwt" for Status List in CWT format

In the case of "application/statuslist+json", the response MUST be of type JSON and follow the rules of . In the case of "application/statuslist+jwt", the response MUST be of type JWT and follow the rules of . In the case of "application/statuslist+cbor", the response MUST be of type CBOR and follow the rules of . In the case of "application/statuslist+cwt", the response MUST be of type CWT and follow the rules of . The HTTP response SHOULD use gzip Content-Encoding as defined in .

Validation Rules Upon receiving a Referenced Token, a Relying Party MUST first perform the validation of the Referenced Token - e.g., checking for expected attributes, valid signature, expiration time. As this is out of scope of this document, this validation is not be described here, but is expected to be done according to the format of the Referenced Token. If this validation was not successful, the Referenced Token MUST be rejected. If the validation was successful, the Relying Party MUST perform the following validation steps to evaluate the status of the reference token:

1. Check for the existence of a status claim, check for the existence of a status_list claim within the status claim and validate that the content of status_list adheres to the rules defined in for JWTs and for CWTs. This step can be overruled if defined within the Referenced Token Format natively
2. Resolve the Status List from the provided URI
3. Validate the Status List Token:
   1. Validate the Status List Token by following the rules defined in section 7.2 of for JWTs and section 7.2 of for CWTs.
   2. Check for the existence of the required claims as defined in and
4. All existing claims in the Status List Token MUST be checked according to the rules in and
   1. The subject claim (sub or 2) of the Status List Token MUST be equal to the uri claim in the status_list object of the Referenced Token
   2. If the Relying Party has custom policies regarding the freshness of the Status List Token, it SHOULD check the issued at claim (iat or 6)
   3. If expiration time is defined (exp or 4), it MUST be checked if the Status List Token is expired
   4. If the Relying Party is using a system for caching the Status List Token, it SHOULD check the ttl claim of the Status List Token and retrieve a fresh copy if (time status was resolved + ttl < current time)
5. Decompress the Status List with a decompressor that is compatible with DEFLATE and ZLIB
6. Retrieve the status value of the index specified in the Referenced Token as described in . Fail if the provided index is out of bound of the status list
7. Check the status value as described in

If any of these checks fails, no statement about the status of the Referenced Token can be made and the Referenced Token SHOULD be rejected.

Status List Aggregation Status List Aggregation is an optional mechanism to retrieve a list of URIs to all Status List Tokens, allowing a Relying Party to fetch all relevant Status Lists for a specific type of Referenced Token or issuer. This mechanism is intended to support fetching and caching mechanisms and allow offline validation of the status of a reference token for a period of time. There are two options for a Relying Party to retrieve the Status List Aggregation. An issuer MAY support any of these mechanisms:

• Issuer metadata: The issuer of the Referenced Token publishes an URI which links to Status List Aggregation, e.g. in publicly available metadata of an issuance protocol
• Status List Parameter: The issuer of the Referenced Token includes an additional claim in the Status List (Token) that contains the Status List Aggregation URI.

Issuer Metadata The issuer MAY link to the Status List Aggregation URI in metadata that can be provided by different means like .well-known metadata as is used commonly in OAuth and OpenID, or via a VICAL extension for ISO mDoc / mDL. The concrete specification on how this is implemented depends on the specific ecosystem and is out of scope of this specification.

Status List Parameter The URI to the Status List Aggregation MAY be provided as the optional parameter aggregation_uri in the Status List itself as explained in and respectively. A Relying Party may use this URI to retrieve an up-to-date list of relevant Status Lists.

Status List Aggregation in JSON Format This section defines the structure for a JSON-encoded Status List Aggregation:

• status_lists: REQUIRED. JSON array of strings that contains URIs linking to Status List (Tokens).

The Status List Aggregation URI provides a list of Status List URIs. This aggregation in JSON and the media type return SHOULD be application/json. A Relying Party can iterate through this list and fetch all Status List Tokens before encountering the specific URI in a Referenced Token. The following is a non-normative example for media type application/json:

Further Examples

Status List Token with 2-Bit Status Values in JWT format In this example, the Status List additionally includes the Status Type "SUSPENDED". As the Status Type value for "SUSPENDED" is 0x02 and does not fit into 1 bit, the "bits" is required to be 2. This example Status List represents the status of 12 Referenced Tokens, requiring 24 bits (3 bytes) of status. These bits are concatenated: Resulting in the byte array and compressed/base64url-encoded status list:

Security Considerations

Correct decoding and parsing of the encoded status list Implementers should be particularly careful for the correct parsing and decoding of the status list. Incorrect implementations might check the index on the wrong data or miscalculate the bit and byte index leading to an erroneous status of the Referenced Token. Beware, that bits are indexed (bit order) from least significant bit to most significant bit (also called "right to left") while bytes are indexed (byte order) in their natural incrementing byte order (usually written for display purpose from left to write). Endianness does not apply here because each status value fits within a single byte. Implementations are RECOMMENDED to verify correctness using the test vectors given by this specification.

Security Guidance for JWT and CWT A Status List Token in the JWT format should follow the security considerations of and the best current practices of . A Status List Token in the CWT format should follow the security considerations of .

Cached and Stale status lists When consumers or verifiers of the Status List fetch the data, they need to be aware of its up-to-date status. The 'ttl' (time-to-live) claim in the Status List Token provides one mechanism for setting a maximum cache time for the fetched data. This property permits distribution of a status list to a CDN or other distribution mechanism while giving guidance to consumers of the status list on how often they need to fetch a fresh copy of the status list even if that status list is not expired.

Privacy Considerations

Observability of Issuers The main privacy consideration for a Status List, especially in the context of the Issuer-Holder-Verifier model , is to prevent the Issuer from tracking the usage of the Referenced Token when the status is being checked. If an Issuer offers status information by referencing a specific token, this would enable him to create a profile for the issued token by correlating the date and identity of Relying Parties, that are requesting the status. The Status List approaches these privacy implications by integrating the status information of many Referenced Tokens into the same list. Therefore, the Issuer does not learn for which Referenced Token the Relying Party is requesting the Status List. The privacy of the Holder is protected by the anonymity within the set of Referenced Tokens in the Status List, also called herd privacy. This limits the possibilities of tracking by the Issuer. The herd privacy is depending on the number of entities within the Status List called its size. A larger size results in better privacy but also impacts the performance as more data has to be transferred to read the Status List. Additionally, the Issuer may analyse data from the HTTP request to identify the Relying Party, e.g. through the sender's IP address. This behaviour may be mitigated by private relay protocols or other mechanism hiding the original sender like .

Malicious Issuers A malicious Issuer could bypass the privacy benefits of the herd privacy by generating a unique Status List for every Referenced Token. By these means, he could maintain a mapping between Referenced Tokens and Status Lists and thus track the usage of Referenced Tokens by utilizing this mapping for the incoming requests. This malicious behaviour could be detected by Relying Parties that request large amounts of Referenced Tokens by comparing the number of different Status Lists and their sizes.

Observability of Relying Parties Once the Relying Party receives the Referenced Token, this enables him to request the Status List to validate its status through the provided uri parameter and look up the corresponding index. However, the Relying Party may persistently store the uri and index of the Referenced Token to request the Status List again at a later time. By doing so regularly, the Relying Party may create a profile of the Referenced Token's validity status. This behaviour may be intended as a feature, e.g. for a KYC process that requires regular validity checks, but might also be abused in cases where this is not intended and unknown to the Holder, e.g. profiling the suspension of a driving license or checking the employment status of an employee credential. TODO elaborate on status list only providing the up-to date/latest status, no historical data, may be provided by the underlying hosting architecture This behaviour could be mitigated by: - regular re-issuance of the Referenced Token, see .

Observability of Outsiders Outside actors may analyse the publicly available Status Lists to get information on the internal processes of the Issuer and his related business. This data may allow inferences on the total number of issued Reference Tokens and the revocation rate. Additionally, actors may regularly fetch this data or use the historic data functionality to learn how these numbers change over time. This behaviour could be mitigated by: - disable the historical data feature (TODO:link) - disable the Status List Aggregation {#batch-fetching} - choose non-sequential, pseudo-random or random indices - use decoy entries to obfuscate the real number of Referenced Tokens within a Status List - choose to deploy and utilize multiple Status Lists simultaneously

Unlinkability Colluding Issuers and Relying Parties have the possibility to link two transactions, as the tuple of uri and index inside the Referenced Token are unique and therefore traceable data. By comparing the status claims of received Referenced Tokens, two colluding Relying Parties could determine that they have interacted with the same user or an Issuer could trace the usage of its issued Referenced Token by colluding with various Relying Parties. It is therefore recommended to use Status Lists for Referenced Token formats that have similar unlinkability properties. To avoid privacy risks for colluding Relying Parties, it is RECOMMENDED that Issuers use batch issuance to issue multiple tokens, see . To avoid further correlatable information by the values of uri and index, Issuers are RECOMMENDED to:

• choose non-sequential, pseudo-random or random indices
• use decoy entries to obfuscate the real number of Referenced Tokens within a Status List
• choose to deploy and utilize multiple Status Lists simultaneously

Third Party Hosting TODO elaborate on increased privacy if the status list is hosted by a third party instead of the issuer reducing tracking possibilities TODO evaluate definition of Status List Provider? An entity that hosts the Status List as a resource for potential Relying Parties. The Status List Provider may be the issuer of the Status List but may also be outsourced to a trusted third party.

Implementation Considerations

Token Lifecycle The lifetime of a Status List (and the Status List Token) depends on the lifetime of its Referenced Tokens. Once all Referenced Tokens are expired, the Issuer may stop serving the Status List (and the Status List Token). Referenced Tokens may be regularly re-issued to mitigate linkability of presentations to Relying Parties. In this case, every re-issued Referenced Token MUST have a fresh Status List entry in order to prevent this becoming possible source of correlation. Referenced Tokens may also be issued in batches, such that Holders can use individual tokens for every transaction. In this case, every Referenced Token MUST have a dedicated Status List entry. Revoking batch issued Referenced Tokens might reveal this correlation later on.

Default Values and Double Allocation Implementations producing Status Lists are RECOMMENDED to initialize the Status List byte array with a default value and provide this as an initialization parameter to the Issuer. The Issuer is RECOMMENDED to use a default value that represents the most common value for its Referenced Tokens to avoid an update during issuance. Implementations producing Status Lists are RECOMMENDED to prevent double allocation, i.e. re-using the same uri and index for multiple Referenced Tokens. The Issuer MUST prevent any unintended double allocation by using the Status List.

Status List Size The Status List Issuer may increase the size of a Status List if it requires indices for additional Referenced Tokens. It is RECOMMENDED that the size of a Status List in bits is divisible in bytes (8 bits) without a remainder, i.e. size-in-bits % 8 = 0. The Status List Issuer may chunk its Referenced Tokens into multiple Status Lists to reduce the transmission size of an individual Status List Token. This may be useful for setups where some entities operate in constrained environments, e.g. for mobile internet or embedded devices.

IANA Considerations

JSON Web Token Claims Registration This specification requests registration of the following Claims in the IANA "JSON Web Token Claims" registry established by .

Registry Contents

• Claim Name: status
• Claim Description: Reference to a status or validity mechanism containing up-to-date status information on the JWT.
• Change Controller: IETF
• Specification Document(s): of this specification

• Claim Name: status_list
• Claim Description: A status list containing up-to-date status information on multiple tokens.
• Change Controller: IETF
• Specification Document(s): of this specification

• Claim Name: ttl
• Claim Description: Time to Live
• Change Controller: IETF
• Specification Document(s): of this specification

JWT Status Mechanism Methods Registry This specification establishes the IANA "Status Mechanism Methods" registry for JWT "status" member values. The registry records the status mechanism method member and a reference to the specification that defines it.

Registration Template Status Method Value:

• The name requested (e.g., "status_list"). The name is case sensitive. Names may not match other registered names in a case-insensitive manner unless the Designated Experts state that there is a compelling reason to allow an exception.

Status Method Description:

• Brief description of the status mechanism method.

Change Controller:

• For Standards Track RFCs, list the "IESG". For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included.

Specification Document(s):

• Reference to the document or documents that specify the parameter, preferably including URIs that can be used to retrieve copies of the documents. An indication of the relevant sections may also be included but is not required.

Initial Registry Contents

• Status Method Value: status_list
• Status Method Description: A status list containing up-to-date status information on multiple tokens.
• Change Controller: IETF
• Specification Document(s): of this specification

CBOR Web Token Claims Registration This specification requests registration of the following Claims in the IANA "CBOR Web Token (CWT) Claims" registry established by .

Registry Contents

• Claim Name: status
• Claim Key: TBD (requested assignment 65535)
• Claim Description: Reference to a status or validity mechanism containing up-to-date status information on the CWT.
• Change Controller: IETF
• Specification Document(s): of this specification

• Claim Name: status_list
• Claim Key: TBD (requested assignment 65533)
• Claim Description: A status list containing up-to-date status information on multiple tokens.
• Change Controller: IETF
• Specification Document(s): of this specification

• Claim Name: ttl
• Claim Key: TBD (requested assignment 65534)
• Claim Description: Time to Live
• Change Controller: IETF
• Specification Document(s): of this specification

CWT Status Mechanism Methods Registry This specification establishes the IANA "Status Mechanism Methods" registry for CWT "status" member values. The registry records the status mechanism method member and a reference to the specification that defines it.

Registration Template Status Method Value:

• The name requested (e.g., "status_list"). The name is case sensitive. Names may not match other registered names in a case-insensitive manner unless the Designated Experts state that there is a compelling reason to allow an exception.

Status Method Description:

• Brief description of the status mechanism method.

Change Controller:

• For Standards Track RFCs, list the "IESG". For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included.

Specification Document(s):

• Reference to the document or documents that specify the parameter, preferably including URIs that can be used to retrieve copies of the documents. An indication of the relevant sections may also be included but is not required.

Initial Registry Contents

• Status Method Value: status_list
• Status Method Description: A status list containing up-to-date status information on multiple tokens.
• Change Controller: IETF
• Specification Document(s): of this specification

Media Type Registration This section requests registration of the following media types in the "Media Types" registry in the manner described in . To indicate that the content is an JSON-based Status List:

• Type name: application
• Subtype name: statuslist+json
• Required parameters: n/a
• Optional parameters: n/a
• Encoding considerations: See of this specification
• Security considerations: See of this specification
• Interoperability considerations: n/a
• Published specification: this specification
• Applications that use this media type: Applications using this specification for updated status information of tokens
• Fragment identifier considerations: n/a
• Additional information: n/a
• Person & email address to contact for further information: Paul Bastian, paul.bastian@posteo.de
• Intended usage: COMMON
• Restrictions on usage: none
• Author: Paul Bastian, paul.bastian@posteo.de
• Change controller: IETF
• Provisional registration? No

To indicate that the content is an JWT-based Status List:

• Type name: application
• Subtype name: statuslist+jwt
• Required parameters: n/a
• Optional parameters: n/a
• Encoding considerations: See of this specification
• Security considerations: See of this specification
• Interoperability considerations: n/a
• Published specification: this specification
• Applications that use this media type: Applications using this specification for updated status information of tokens
• Fragment identifier considerations: n/a
• Additional information: n/a
• Person & email address to contact for further information: Paul Bastian, paul.bastian@posteo.de
• Intended usage: COMMON
• Restrictions on usage: none
• Author: Paul Bastian, paul.bastian@posteo.de
• Change controller: IETF
• Provisional registration? No

To indicate that the content is an CBOR-based Status List:

• Type name: application
• Subtype name: statuslist+cbor
• Required parameters: n/a
• Optional parameters: n/a
• Encoding considerations: See of this specification
• Security considerations: See of this specification
• Interoperability considerations: n/a
• Published specification: this specification
• Applications that use this media type: Applications using this specification for updated status information of tokens
• Fragment identifier considerations: n/a
• Additional information: n/a
• Person & email address to contact for further information: Paul Bastian, paul.bastian@posteo.de
• Intended usage: COMMON
• Restrictions on usage: none
• Author: Paul Bastian, paul.bastian@posteo.de
• Change controller: IETF
• Provisional registration? No

To indicate that the content is an CWT-based Status List:

• Type name: application
• Subtype name: statuslist+cwt
• Required parameters: n/a
• Optional parameters: n/a
• Encoding considerations: See of this specification
• Security considerations: See of this specification
• Interoperability considerations: n/a
• Published specification: this specification
• Applications that use this media type: Applications using this specification for updated status information of tokens
• Fragment identifier considerations: n/a
• Additional information: n/a
• Person & email address to contact for further information: Paul Bastian, paul.bastian@posteo.de
• Intended usage: COMMON
• Restrictions on usage: none
• Author: Paul Bastian, paul.bastian@posteo.de
• Change controller: IETF
• Provisional registration? No

References Normative References This specification defines a lossless compressed data format. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. This specification defines a lossless compressed data format that compresses data using a combination of the LZ77 algorithm and Huffman coding, with efficiency comparable to the best currently available general-purpose compression methods. This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. This second document defines the general structure of the MIME media typing system and defines an initial set of media types. [STANDARDS-TRACK] A Uniform Resource Identifier (URI) is a compact sequence of characters that identifies an abstract or physical resource. This specification defines the generic URI syntax and a process for resolving URI references that might be in relative form, along with guidelines and security considerations for the use of URIs on the Internet. The URI syntax defines a grammar that is a superset of all valid URIs, allowing an implementation to parse the common components of a URI reference without knowing the scheme-specific requirements of every possible identifier. This specification does not define a generative grammar for URIs; that task is performed by the individual specifications of each URI scheme. [STANDARDS-TRACK] Many application technologies enable secure communication between two entities by means of Internet Public Key Infrastructure Using X.509 (PKIX) certificates in the context of Transport Layer Security (TLS). This document specifies procedures for representing and verifying the identity of application services in such interactions. [STANDARDS-TRACK] This document defines procedures for the specification and registration of media types for use in HTTP, MIME, and other Internet protocols. This memo documents an Internet Best Current Practice. JSON Web Signature (JWS) represents content secured with digital signatures or Message Authentication Codes (MACs) using JSON-based data structures. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and an IANA registry defined by that specification. Related encryption capabilities are described in the separate JSON Web Encryption (JWE) specification. JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted. JavaScript Object Notation (JSON) is a lightweight, text-based, language-independent data interchange format. It was derived from the ECMAScript Programming Language Standard. JSON defines a small set of formatting rules for the portable representation of structured data. This document removes inconsistencies with other specifications of JSON, repairs specification errors, and offers experience-based interoperability guidance. CBOR Web Token (CWT) is a compact means of representing claims to be transferred between two parties. The claims in a CWT are encoded in the Concise Binary Object Representation (CBOR), and CBOR Object Signing and Encryption (COSE) is used for added application-layer security protection. A claim is a piece of information asserted about a subject and is represented as a name/value pair consisting of a claim name and a claim value. CWT is derived from JSON Web Token (JWT) but uses CBOR rather than JSON. JSON Web Tokens, also known as JWTs, are URL-safe JSON-based security tokens that contain a set of claims that can be signed and/or encrypted. JWTs are being widely used and deployed as a simple security token format in numerous protocols and applications, both in the area of digital identity and in other application areas. This Best Current Practices document updates RFC 7519 to provide actionable guidance leading to secure implementation and deployment of JWTs. The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack. This document obsoletes RFC 7049, providing editorial improvements, new details, and errata fixes while keeping full compatibility with the interchange format of RFC 7049. It does not create a new version of the format. Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need to be able to define basic security services for this data format. This document defines the CBOR Object Signing and Encryption (COSE) protocol. This specification describes how to create and process signatures, message authentication codes, and encryption using CBOR for serialization. This specification additionally describes how to represent cryptographic keys using CBOR. This document, along with RFC 9053, obsoletes RFC 8152. The Hypertext Transfer Protocol (HTTP) is a stateless application-level protocol for distributed, collaborative, hypertext information systems. This document describes the overall architecture of HTTP, establishes common terminology, and defines aspects of the protocol that are shared by all versions. In this definition are core protocol elements, extensibility mechanisms, and the "http" and "https" Uniform Resource Identifier (URI) schemes. This document updates RFC 3864 and obsoletes RFCs 2818, 7231, 7232, 7233, 7235, 7538, 7615, 7694, and portions of 7230. This specification adds the equivalent of the JSON Object Signing and Encryption (JOSE) "typ" (type) header parameter to CBOR Object Signing and Encryption (COSE). This enables the benefits of explicit typing (as defined in RFC 8725, "JSON Web Token Best Current Practices") to be brought to COSE objects. The syntax of the COSE type header parameter value is the same as the existing COSE content type header parameter. IANA n.d. IANA n.d. IANA n.d. IANA n.d. WHATWG n.d. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References The OAuth 2.0 authorization framework enables a third-party application to obtain limited access to an HTTP service, either on behalf of a resource owner by orchestrating an approval interaction between the resource owner and the HTTP service, or by allowing the third-party application to obtain access on its own behalf. This specification replaces and obsoletes the OAuth 1.0 protocol described in RFC 5849. [STANDARDS-TRACK] This specification defines a method for a protected resource to query an OAuth 2.0 authorization server to determine the active state of an OAuth 2.0 token and to determine meta-information about this token. OAuth 2.0 deployments can use this method to convey information about the authorization context of the token from the authorization server to the protected resource. This specification describes how to declare in a JSON Web Token (JWT) that the presenter of the JWT possesses a particular proof-of- possession key and how the recipient can cryptographically confirm proof of possession of the key by the presenter. Being able to prove possession of a key is also sometimes described as the presenter being a holder-of-key. This document describes Oblivious HTTP, a protocol for forwarding encrypted HTTP messages. Oblivious HTTP allows a client to make multiple requests to an origin server without that server being able to link those requests to the client or to identify the requests as having come from the same client, while placing only limited trust in the nodes used to forward the messages. MATTR Authlete Inc. Ping Identity This specification describes data formats as well as validation and processing rules to express Verifiable Credentials with JSON payloads with and without selective disclosure based on the SD-JWT [I-D.ietf-oauth-selective-disclosure-jwt] format. ISO/IEC JTC 1/SC 17 n.d.

Acknowledgments We would like to thank Brian Campbell, Filip Skokan, Francesco Marino, Guiseppe De Marco, Kristina Yasuda, Markus Kreusch, Martijn Haring, Michael B. Jones, Mike Prorock, Oliver Terbu, Orie Steele, Timo Glastra and Torsten Lodderstedt for their valuable contributions, discussions and feedback to this specification.

Document History -04

• add mDL example as Referenced Token and consolidate CWT and CBOR sections
• add implementation consideration for Default Values, Double Allocation and Status List Size
• add privacy consideration on using private relay protocols
• add privacy consideration on observability of outsiders
• add security considerations on correct parsing and decoding
• remove requirement for matching iss claim in Referenced Token and Status List Token
• add sd-jwt-vc example
• fix CWT status_list map encoding
• editorial fixes
• add CORS considerations to the http endpoint
• fix reference of Status List in CBOR format
• added status_list CWT claim key assigned
• move base64url definition to terminology

-03

• remove unused reference to RFC9111
• add validation rules for status list token
• introduce the status list aggregation mechanism
• relax requirements for status_list claims to contain other parameters
• change cwt referenced token example to hex and annotated hex
• require TLS only for fetching Status List, not for Status List Token
• remove the undefined phrase Status List endpoint
• remove http caching in favor of the new ttl claim
• clarify the sub claim of Status List Token
• relax status_list iss requirements for CWT
• Fixes missing parts & iana ttl registration in CWT examples

-02

• add ttl claim to Status List Token to convey caching
• relax requirements on referenced token
• clarify Deflate / zlib compression
• make a reference to the Issuer-Holder-Verifier model of SD-JWT VC
• add COSE/CWT/CBOR encoding

-01

• Rename title of the draft
• add design consideration to the introduction
• Change status claim to in referenced token to allow re-use for other mechanisms
• Add IANA Registry for status mechanisms
• restructure the sections of this document
• add option to return an unsigned Status List
• Changing compression from gzip to zlib
• Change typo in Status List Token sub claim description
• Add access token as an example use-case

-00

• Initial draft after working group adoption
• update acknowledgments
• renamed Verifier to Relying Party
• added IANA consideration

[ draft-ietf-oauth-status-list ] -01

• Applied editorial improvements suggested by Michael Jones.

-00

• Initial draft