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Token Status List
draft-ietf-oauth-status-list-02

Document Type Active Internet-Draft (oauth WG)
Authors Tobias Looker , Paul Bastian , Christian Bormann
Last updated 2024-03-03
Replaces draft-looker-oauth-jwt-cwt-status-list
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draft-ietf-oauth-status-list-02
Network Working Group                                          T. Looker
Internet-Draft                                                     MATTR
Intended status: Informational                                P. Bastian
Expires: 5 September 2024                                               
                                                              C. Bormann
                                                            4 March 2024

                           Token Status List
                    draft-ietf-oauth-status-list-02

Abstract

   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

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at
   https://vcstuff.github.io/draft-ietf-oauth-status-list/draft-ietf-
   oauth-status-list.html.  Status information for this document may be
   found at https://datatracker.ietf.org/doc/draft-ietf-oauth-status-
   list/.

   Source for this draft and an issue tracker can be found at
   https://github.com/vcstuff/draft-ietf-oauth-status-list.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

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   This Internet-Draft will expire on 5 September 2024.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Rationale . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Design Considerations . . . . . . . . . . . . . . . . . .   5
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   6
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Status List . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Status List in JSON Format  . . . . . . . . . . . . . . .   8
     4.2.  Status List in CBOR Format  . . . . . . . . . . . . . . .   8
   5.  Status List Token . . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Status List Token in JWT Format . . . . . . . . . . . . .   9
     5.2.  Status List Token in CWT Format . . . . . . . . . . . . .  11
   6.  Referenced Token  . . . . . . . . . . . . . . . . . . . . . .  12
     6.1.  Status Claim  . . . . . . . . . . . . . . . . . . . . . .  12
     6.2.  Referenced Token in JWT Format  . . . . . . . . . . . . .  13
     6.3.  Referenced Token in CWT Format  . . . . . . . . . . . . .  14
     6.4.  Referenced Token in other COSE/CBOR Format  . . . . . . .  15
   7.  Status Types  . . . . . . . . . . . . . . . . . . . . . . . .  16
     7.1.  Status Types Values . . . . . . . . . . . . . . . . . . .  16
   8.  Verification and Processing . . . . . . . . . . . . . . . . .  16
     8.1.  Status List Request . . . . . . . . . . . . . . . . . . .  16
     8.2.  Status List Response  . . . . . . . . . . . . . . . . . .  17
     8.3.  Caching . . . . . . . . . . . . . . . . . . . . . . . . .  17
     8.4.  Validation Rules  . . . . . . . . . . . . . . . . . . . .  18
   9.  Further Examples  . . . . . . . . . . . . . . . . . . . . . .  18
     9.1.  Status List Token with 2-Bit Status Values in JWT
           format  . . . . . . . . . . . . . . . . . . . . . . . . .  18
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  19
     10.1.  Correct decoding and parsing of the encoded status
            list . . . . . . . . . . . . . . . . . . . . . . . . . .  19
     10.2.  Cached and Stale status lists  . . . . . . . . . . . . .  19

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     10.3.  Authorized access to the Status List . . . . . . . . . .  19
     10.4.  History  . . . . . . . . . . . . . . . . . . . . . . . .  19
   11. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  19
     11.1.  Limiting issuers observability of token verification . .  19
     11.2.  Malicious Issuers  . . . . . . . . . . . . . . . . . . .  20
     11.3.  Unobservability of Relying Parties . . . . . . . . . . .  20
     11.4.  Unlinkability  . . . . . . . . . . . . . . . . . . . . .  21
     11.5.  Third Party Hosting  . . . . . . . . . . . . . . . . . .  21
   12. Implementation Considerations . . . . . . . . . . . . . . . .  21
     12.1.  Token Lifecycle  . . . . . . . . . . . . . . . . . . . .  21
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
     13.1.  JSON Web Token Claims Registration . . . . . . . . . . .  22
       13.1.1.  Registry Contents  . . . . . . . . . . . . . . . . .  22
     13.2.  JWT Status Mechanism Methods Registry  . . . . . . . . .  22
       13.2.1.  Registration Template  . . . . . . . . . . . . . . .  23
       13.2.2.  Initial Registry Contents  . . . . . . . . . . . . .  23
     13.3.  CBOR Web Token Claims Registration . . . . . . . . . . .  23
       13.3.1.  Registry Contents  . . . . . . . . . . . . . . . . .  23
     13.4.  CWT Status Mechanism Methods Registry  . . . . . . . . .  24
       13.4.1.  Registration Template  . . . . . . . . . . . . . . .  24
       13.4.2.  Initial Registry Contents  . . . . . . . . . . . . .  25
     13.5.  Media Type Registration  . . . . . . . . . . . . . . . .  25
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  28
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  29
     14.2.  Informative References . . . . . . . . . . . . . . . . .  31
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  31
   Document History  . . . . . . . . . . . . . . . . . . . . . . . .  31
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  33

1.  Introduction

   Token formats secured by JOSE [IANA.JOSE] or COSE [RFC9052], such as
   JSON Web Tokens (JWTs) [RFC7519], CBOR Web Tokens (CWTs) [RFC8392]
   and ISO mdoc [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 by an endpoint or be signed and

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   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 [RFC6749].  Token
   Introspection [RFC7662] 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 [SD-JWT.VC].  The
   following diagram depicts the basic conceptual relationship.

   +-------------------+                  +------------------------+
   |                   | describes status |                        |
   |    Status List    +----------------->|    Referenced Token    |
   |   (JSON or CBOR)  <------------------+      (JOSE, COSE)      |
   |                   |   references     |                        |
   +-------+-----------+                  +--------+---------------+
           |
           |embedded in
           v
   +-------------------+
   |                   |
   | Status List Token |
   |  (JWT or CWT)     |
   |                   |
   +-------------------+

1.1.  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

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   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.

1.2.  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

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2.  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 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  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 [RFC8259] or CBOR [RFC8949] for
      representation of the token and secure it using JSON Object
      Signing as defined in [RFC7515] or CBOR Object Signing and
      Encryption as defined in [RFC9052].  The information from the
      contained Status List may give a Relying Party additional
      information about up-to-date status of the Referenced Token.

4.  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.

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   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 [RFC1951] with the
       ZLIB [RFC1950] 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:

   status[0] = 1
   status[1] = 0
   status[2] = 0
   status[3] = 1
   status[4] = 1
   status[5] = 1
   status[6] = 0
   status[7] = 1
   status[8] = 1
   status[9] = 1
   status[10] = 0
   status[11] = 0
   status[12] = 0
   status[13] = 1
   status[14] = 0
   status[15] = 1

   These bits are concatenated:

   byte             0                  1               2
   bit       7 6 5 4 3 2 1 0    7 6 5 4 3 2 1 0    7
            +-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+-+  +-+...
   values   |1|0|1|1|1|0|0|1|  |1|0|1|0|0|0|1|1|  |0|...
            +-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+-+  +-+...
   index     7 6 5 4 3 2 1 0   15   ...  10 9 8   23
            \_______________/  \_______________/
                   0xB9               0xA3

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4.1.  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.
      The object contains exactly two 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 (as defined in Section 2 of
         [RFC7515]) Status List as specified in Section 4.

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

   byte_array = [0xb9, 0xa3]
   encoded:
   {
     "bits": 1,
     "lst": "eNrbuRgAAhcBXQ"
   }

4.2.  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 Section 4.1.

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

   byte_array = [0xb9, 0xa3]
   encoded:
   a2646269747301636c73744a78dadbb918000217015d

   The following is the CBOR diagnostic output of the example above:

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   a2                              # map(2)
     64                            #   string(4)
       62697473                    #     "bits"
     01                            #   uint(1)
     63                            #   string(3)
       6c7374                      #     "lst"
     4a                            #   bytes(10)
       78dadbb918000217015d        #     "xÚÛ¹\x18\x00\x02\x17\x01]"

5.  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.

5.1.  Status List Token in JWT Format

   The Status List Token MUST be encoded as a "JSON Web Token (JWT)"
   according to [RFC7519].

   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:

   *  iss: REQUIRED when also present in the Referenced Token.  The iss
      (issuer) claim MUST specify a unique string identifier for the
      entity that issued the Status List Token.  In the absence of an
      application profile specifying otherwise, compliant applications
      MUST compare issuer values using the Simple String Comparison
      method defined in Section 6.2.1 of [RFC3986].  The value MUST be
      equal to that of the iss claim contained within the Referenced
      Token.

   *  sub: REQUIRED.  The sub (subject) claim MUST specify a unique
      string identifier for 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.

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   *  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
      Section 4.1.

   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)" [RFC7519].

   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:

   {
     "alg": "ES256",
     "kid": "12",
     "typ": "statuslist+jwt"
   }
   .
   {
     "exp": 2291720170,
     "iat": 1686920170,
     "iss": "https://example.com",
     "status_list": {
       "bits": 1,
       "lst": "eNrbuRgAAhcBXQ"
     },
     "sub": "https://example.com/statuslists/1"
   }

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5.2.  Status List Token in CWT Format

   The Status List Token MUST be encoded as a "CBOR Web Token (CWT)"
   according to [RFC8392].

   The following content applies to the CWT protected header:

   *  16 TBD (type): REQUIRED.  The type of the CWT MUST be
      statuslist+cwt as defined in [CWT.typ].

   The following content applies to the CWT Claims Set:

   *  1 (issuer): REQUIRED.  Same definition as iss claim in
      Section 5.1.

   *  2 (subject): REQUIRED.  Same definition as sub claim in
      Section 5.1.

   *  6 (issued at): REQUIRED.  Same definition as iat claim in
      Section 5.1.

   *  4 (expiration time): OPTIONAL.  Same definition as exp claim in
      Section 5.1.

   *  65534 (status list): REQUIRED.  The status list claim MUST specify
      the Status List conforming to the rules outlined in Section 4.2.

   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)" [RFC8392].

   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 (not including the type header yet):

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   d28453a20126106e7374617475736c6973742b637774a1044231325860a502782168
   747470733a2f2f6578616d706c652e636f6d2f7374617475736c697374732f310173
   68747470733a2f2f6578616d706c652e636f6d061a648c5bea041a8898dfea19fffe
   56a2646269747301636c73744a78dadbb918000217015d58400f2ca3772e10b09d5d
   6ed56461f7cba1a816c6234072d1bb693db277048e5db5a4e64444492a9b781d6c7a
   c9714db99cc7aadb3812ec90cab7794170bab5b473

   The following is the CBOR diagnostic output of the example above:

d2                              # tag(18)
  84                            #   array(4)
    53                          #     bytes(19)
      a20126106e7374617475736c  #       "¢\x01&\x10nstatusl"
      6973742b637774            #       "ist+cwt"
    a1                          #     map(1)
      04                        #       uint(4)
      42                        #       bytes(2)
        3132                    #         "12"
    58 60                       #     bytes(96)
      a502782168747470733a2f2f  #       "¥\x02x!https://"
      6578616d706c652e636f6d2f  #       "example.com/"
      7374617475736c697374732f  #       "statuslists/"
      31017368747470733a2f2f65  #       "1\x01shttps://e"
      78616d706c652e636f6d061a  #       "xample.com\x06\x1a"
      648c3fca041a8898c3ca19ff  #       "d\x8c?Ê\x04\x1a\x88\x98ÃÊ\x19ÿ"
      fe56a2646269747301636c73  #       "þV¢dbits\x01cls"
      744a78dadbb918000217015d  #       "tJxÚÛ¹\x18\x00\x02\x17\x01]"
    58 40                       #     bytes(64)
      3fd60a6d10eb4b4131f1f6c1  #       "?Ö\x0am\x10ëKA1ñöÁ"
      2fb365ae27b969e8e8df0b4f  #       "/³e®'¹ièèß\x0bO"
      4029815b679cb1051c1c9eb3  #       "@)\x81[g\x9c±\x05\x1c\x1c\x9e³"
      6aa72f6f17bcfdb5ed443bdf  #       "j§/o\x17¼ýµíD;ß"
      c2339568ab42949169b413e7  #       "Â3\x95h«B\x94\x91i´\x13ç"
      02ae1e6a                  #       "\x02®\x1ej"

6.  Referenced Token

6.1.  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 [RFC7800] in which
   different authenticity confirmation methods can be included.

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6.2.  Referenced Token in JWT Format

   The Referenced Token MUST be encoded as a "JSON Web Token (JWT)"
   according to [RFC7519].

   The following content applies to the JWT Claims Set:

   *  iss: REQUIRED when also present in the Status List Token.  The iss
      (issuer) claim MUST specify a unique string identifier for the
      entity that issued the Referenced Token.  In the absence of an
      application profile specifying otherwise, compliant applications
      MUST compare issuer values using the Simple String Comparison
      method defined in Section 6.2.1 of [RFC3986].  The value MUST be
      equal to that of the iss claim contained within the referenced
      Status List Token.

   *  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.  The object contains exactly
         two claims:

         o  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.

         o  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 [RFC3986].

   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:

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   {
     "alg": "ES256",
     "kid": "11"
   }
   .
   {
     "iss": "https://example.com",
     "status": {
       "status_list": {
         "idx": 0,
         "uri": "https://example.com/statuslists/1"
       }
     }
   }

6.3.  Referenced Token in CWT Format

   The Referenced Token MUST be encoded as a "COSE Web Token (CWT)"
   object according to [RFC8392].

   The following content applies to the CWT Claims Set:

   *  1 (issuer): REQUIRED.  Same definition as iss claim in
      Section 6.2.

   *  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 Section 6.2 but
         MUST be encoded as a StatusListInfo CBOR structure with the
         following fields:

         o  idx: REQUIRED.  Same definition as idx claim in Section 6.2.

         o  uri: REQUIRED.  Same definition as uri claim in Section 6.2.

   Application of additional restrictions and policy are at the
   discretion of the verifying party.

   The following is a non-normative example for a decoded payload of a
   Referenced Token:

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   18(
       [
         / protected / << {
           / alg / 1: -7 / ES256 /
         } >>,
         / unprotected / {
           / kid / 4: h'3132' / '13' /
         },
         / payload / << {
           / iss    / 1: "https://example.com",
           / status / 65535: {
             "status_list": {
               "idx": "0",
               "uri": "https://example.com/statuslists/1"
             }
           }
         } >>,
         / signature / h'...'
       ]
     )

6.4.  Referenced Token in other COSE/CBOR Format

   The Referenced Token MUST be encoded as a COSE_Sign1 or COSE_Sign
   CBOR structure as defined in "CBOR Object Signing and Encryption
   (COSE)" [RFC9052].

   It is required to encode the status mechanisms referred to in the
   Referenced Token using the Status CBOR structure defined in
   Section 6.3.

   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 a decoded payload of a
   Referenced Token:

   TBD: example

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7.  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.

7.1.  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.

8.  Verification and Processing

8.1.  Status List Request

   To obtain the Status List or Status List Token, the Relying Party
   MUST send a HTTP GET request to the Status List Endpoint.
   Communication with the Status List Endpoint 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
   [RFC6125].

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   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.

8.2.  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 Section 4.1.  In the case of
   "application/statuslist+jwt", the response MUST be of type JWT and
   follow the rules of Section 5.1.  In the case of "application/
   statuslist+cbor", the response MUST be of type CBOR and follow the
   rules of Section 4.2.  In the case of "application/statuslist+cwt",
   the response MUST be of type CWT and follow the rules of Section 5.2.

   The HTTP response SHOULD use gzip Content-Encoding as defined in
   [RFC9110].

8.3.  Caching

   If caching is required (e.g., to enable the use of alternative
   mechanisms for hosting, like Content Delivery Networks), the control
   of the caching mechanism SHOULD be implemented using the standard
   HTTP Cache-Control as defined in [RFC9111].

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8.4.  Validation Rules

   TBD

9.  Further Examples

9.1.  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.

   status[0] = 1
   status[1] = 2
   status[2] = 0
   status[3] = 3
   status[4] = 0
   status[5] = 1
   status[6] = 0
   status[7] = 1
   status[8] = 1
   status[9] = 2
   status[10] = 3
   status[11] = 3

   These bits are concatenated:

   byte             0                  1                  2
   bit       7 6 5 4 3 2 1 0    7 6 5 4 3 2 1 0    7 6 5 4 3 2 1 0
            +-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+-+
   values   |1|1|0|0|1|0|0|1|  |0|1|0|0|0|1|0|0|  |1|1|1|1|1|0|0|1|
            +-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+-+  +-+-+-+-+-+-+-+-+
             \ / \ / \ / \ /    \ / \ / \ / \ /    \ / \ / \ / \ /
   status     3   0   2   1      1   0   1   0      3   3   2   1
   index      3   2   1   0      7   6   5   4      11  10  9   8
              \___________/      \___________/      \___________/
                   0xC9               0x44               0xF9

   Resulting in the byte array and compressed/base64url encoded status
   list:

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   byte_array = [0xc9, 0x44, 0xf9]
   encoded:
   {
     "bits": 2,
     "lst": "eNo76fITAAPfAgc"
   }

10.  Security Considerations

10.1.  Correct decoding and parsing of the encoded status list

   TODO elaborate on risks of incorrect parsing/decoding leading to
   erroneous status data

10.2.  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.

10.3.  Authorized access to the Status List

   TODO elaborate on authorization mechanisms preventing misuse and
   profiling as described in privacy section

10.4.  History

   TODO elaborate on status list only providing the up-to date/latest
   status, no historical data, may be provided by the underlying hosting
   architecture

11.  Privacy Considerations

11.1.  Limiting issuers observability of token verification

   The main privacy consideration for a Status List, especially in the
   context of the Issuer-Holder-Verifier model [SD-JWT.VC], 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.

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   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.

11.2.  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.

11.3.  Unobservability 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.

   This behaviour could be mitigated by: - adding authorization rules to
   the Status List, see Section 10.3. - regular re-issuance of the
   Referenced Token, see Section 12.1.

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11.4.  Unlinkability

   Colluding Issuers and a 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 Section 12.1.

   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 or dead entries to obfuscate the real number of
      Referenced Tokens within a Status List

   *  choose to deploy and utilize multiple Status Lists simultaneously

11.5.  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.

12.  Implementation Considerations

12.1.  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 increase security or
   to mitigate linkability and prevent tracking by Relying Parties.  In
   this case, every Referenced Token MUST have a fresh Status List
   entry.

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   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.

13.  IANA Considerations

13.1.  JSON Web Token Claims Registration

   This specification requests registration of the following Claims in
   the IANA "JSON Web Token Claims" registry [IANA.JWT] established by
   [RFC7519].

13.1.1.  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): Section 6.1 of this specification

   *  Claim Name: status_list

   *  Claim Description: A status list containing up-to-date status
      information on multiple other JWTs encoded as a bitarray.

   *  Change Controller: IETF

   *  Specification Document(s): Section 5.1 of this specification

   *  Claim Name: ttl

   *  Claim Description: Time to Live

   *  Change Controller: IETF

   *  Specification Document(s): Section 5.1 of this specification

13.2.  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.

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13.2.1.  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.

13.2.2.  Initial Registry Contents

   *  Status Method Value: status_list

   *  Status Method Description: A status list containing up-to-date
      status information on multiple other JWTs encoded as a bitarray.

   *  Change Controller: IETF

   *  Specification Document(s): Section 6.2 of this specification

13.3.  CBOR Web Token Claims Registration

   This specification requests registration of the following Claims in
   the IANA "CBOR Web Token (CWT) Claims" registry [IANA.CWT]
   established by [RFC8392].

13.3.1.  Registry Contents

   *  Claim Name: status

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   *  Claim Description: Reference to a status or validity mechanism
      containing up-to-date status information on the CWT.

   *  Change Controller: IETF

   *  Specification Document(s): Section 6.1 of this specification

   *  Claim Name: status_list

   *  Claim Description: A status list containing up-to-date status
      information on multiple other CWTs encoded as a bitarray.

   *  Change Controller: IETF

   *  Specification Document(s): Section 5.2 of this specification

13.4.  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.

13.4.1.  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.

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13.4.2.  Initial Registry Contents

   *  Status Method Value: status_list

   *  Status Method Description: A status list containing up-to-date
      status information on multiple other CWTs encoded as a bitarray.

   *  Change Controller: IETF

   *  Specification Document(s): Section 6.3 of this specification

13.5.  Media Type Registration

   This section requests registration of the following media types
   [RFC2046] in the "Media Types" registry [IANA.MediaTypes] in the
   manner described in [RFC6838].

   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: binary; A JSON-based Status List is a
      JSON Object.

   *  Security considerations: See (#Security) 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:

      -  File extension(s): n/a

      -  Macintosh file type code(s): n/a

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   *  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: binary; A JWT-based Status List is a JWT;
      JWT values are encoded as a series of base64url-encoded values
      (some of which may be the empty string) separated by period ('.')
      characters.

   *  Security considerations: See (#Security) 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:

      -  File extension(s): n/a

      -  Macintosh file type code(s): n/a

   *  Person & email address to contact for further information: Paul
      Bastian, paul.bastian@posteo.de

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   *  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: binary; A CBOR-based Status List is a
      CBOR Object.

   *  Security considerations: See (#Security) 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:

      -  File extension(s): n/a

      -  Macintosh file type code(s): 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

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   *  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: binary;

   *  Security considerations: See (#Security) 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:

      -  File extension(s): n/a

      -  Macintosh file type code(s): 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

14.  References

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14.1.  Normative References

   [CWT.typ]  Jones, M. B. and O. Steele, "COSE "typ" (type) Header
              Parameter", Work in Progress, Internet-Draft, draft-ietf-
              cose-typ-header-parameter-03, 26 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-cose-
              typ-header-parameter-03>.

   [IANA.CWT] IANA, "CBOR Web Token (CWT) Claims", n.d.,
              <https://www.iana.org/assignments/cwt/cwt.xhtml>.

   [IANA.JOSE]
              IANA, "JSON Object Signing and Encryption (JOSE)", n.d.,
              <https://www.iana.org/assignments/jose/jose.xhtml>.

   [IANA.JWT] IANA, "JSON Web Token Claims", n.d.,
              <https://www.iana.org/assignments/jwt/jwt.xhtml>.

   [IANA.MediaTypes]
              IANA, "Media Types", n.d.,
              <https://www.iana.org/assignments/media-types/media-
              types.xhtml>.

   [RFC1950]  Deutsch, P. and J. Gailly, "ZLIB Compressed Data Format
              Specification version 3.3", RFC 1950,
              DOI 10.17487/RFC1950, May 1996,
              <https://www.rfc-editor.org/rfc/rfc1950>.

   [RFC1951]  Deutsch, P., "DEFLATE Compressed Data Format Specification
              version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
              <https://www.rfc-editor.org/rfc/rfc1951>.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              DOI 10.17487/RFC2046, November 1996,
              <https://www.rfc-editor.org/rfc/rfc2046>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/rfc/rfc3986>.

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   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
              2011, <https://www.rfc-editor.org/rfc/rfc6125>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/rfc/rfc6838>.

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <https://www.rfc-editor.org/rfc/rfc7515>.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <https://www.rfc-editor.org/rfc/rfc7519>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/rfc/rfc8259>.

   [RFC8392]  Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
              "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
              May 2018, <https://www.rfc-editor.org/rfc/rfc8392>.

   [RFC8949]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", STD 94, RFC 8949,
              DOI 10.17487/RFC8949, December 2020,
              <https://www.rfc-editor.org/rfc/rfc8949>.

   [RFC9052]  Schaad, J., "CBOR Object Signing and Encryption (COSE):
              Structures and Process", STD 96, RFC 9052,
              DOI 10.17487/RFC9052, August 2022,
              <https://www.rfc-editor.org/rfc/rfc9052>.

   [RFC9110]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", STD 97, RFC 9110,
              DOI 10.17487/RFC9110, June 2022,
              <https://www.rfc-editor.org/rfc/rfc9110>.

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   [RFC9111]  Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Caching", STD 98, RFC 9111,
              DOI 10.17487/RFC9111, June 2022,
              <https://www.rfc-editor.org/rfc/rfc9111>.

14.2.  Informative References

   [ISO.mdoc] ISO/IEC JTC 1/SC 17, "ISO/IEC 18013-5:2021 ISO-compliant
              driving licence", n.d..

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <https://www.rfc-editor.org/rfc/rfc6749>.

   [RFC7662]  Richer, J., Ed., "OAuth 2.0 Token Introspection",
              RFC 7662, DOI 10.17487/RFC7662, October 2015,
              <https://www.rfc-editor.org/rfc/rfc7662>.

   [RFC7800]  Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-
              Possession Key Semantics for JSON Web Tokens (JWTs)",
              RFC 7800, DOI 10.17487/RFC7800, April 2016,
              <https://www.rfc-editor.org/rfc/rfc7800>.

   [SD-JWT.VC]
              Terbu, O., Fett, D., and B. Campbell, "SD-JWT-based
              Verifiable Credentials (SD-JWT VC)", Work in Progress,
              Internet-Draft, draft-ietf-oauth-sd-jwt-vc-02, 27 February
              2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
              oauth-sd-jwt-vc-02>.

Acknowledgments

   We would like to thank Brian Campbell, Filip Skokan, Francesco
   Marino, Guiseppe De Marco, Kristina Yasuda, 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

   -02

   *  add ttl claim to Status List Token to convey caching

   *  relax requirements on referenced token

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   *  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

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Authors' Addresses

   Tobias Looker
   MATTR
   Email: tobias.looker@mattr.global

   Paul Bastian
   Email: paul.bastian@posteo.de

   Christian Bormann
   Email: chris.bormann@gmx.de

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