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Aries RFC 0721: Revocation Notification 2.0

Summary

This RFC defines the message format which an issuer uses to notify a holder that a previously issued credential has been revoked.

Change Log

  • 20240320: Clarification removing references to retired ~please_ack decorator and RFC.

Motivation

We need a standard protocol for an issuer to notify a holder that a previously issued credential has been revoked or unrevoked.

For example, suppose a passport agency revokes Alice's passport. The passport agency (an issuer) may want to notify Alice (a holder) that her passport has been revoked so that she knows that she will be unable to use her passport to travel.

Tutorial

The Revocation Notification protocol is a very simple protocol consisting of two messages:

  • Revoke - issuer to holder
  • Unrevoke - issuer to holder

This simple protocol allows an issuer to choose to notify a holder that a previously issued credential has been revoked or unrevoked.

It is the issuer's prerogative whether or not to notify the holder that a credential has been (un)revoked. It is not a security risk if the issuer does not notify the holder that the credential has been (un)revoked, nor if the message is lost. The holder will still be unable to use a revoked credential without this notification.

Roles

There are two parties involved in a Revocation Notification: issuer and holder. The issuer sends the revoke or unrevoke message to the holder.

Messages

Revoke

The revoke message sent by the issuer to the holder. The holder should verify that the revoke message came from the connection that was originally used to issue the credential.

Message format:

{
  "@type": "https://didcomm.org/revocation_notification/2.1/revoke",
  "@id": "<uuid-revocation-notification>",
  "revocation_format": "<revocation_format>",
  "credential_id": "<credential_id>",
  "comment": "Some comment"
}

Description of fields:

  • revocation_format (required) -- the format of the credential revocation. Accepted values for the revocation format are provided in the "Revocation Credential Identification Formats" section immediately below.

  • credential_id (required) -- the individual credential identifier of a credential issued using the issue-credential-v2 protocol that has been revoked by the issuer. Accepted values for the credential id format are provided in the "Revocation Credential Identification Formats" section immediately below.

  • comment (optional) -- a field that provides some human readable information about the revocation notification. This is typically the reason for the revocation as deemed appropriate by the issuer.

Unrevoke

The unrevoke message sent by the issuer to the holder. The holder should verify that the unrevoke message came from the connection that was originally used to issue the credential.

Message format:

{
  "@type": "https://didcomm.org/revocation_notification/2.1/unrevoke",
  "@id": "<uuid-revocation-notification>",
  "revocation_format": "<revocation_format>",
  "credential_id": "<credential_id>",
  "comment": "Some comment"
}

Description of fields:

  • revocation_format (required) -- the format of the credential revocation. Accepted values for the revocation format are provided in the "Revocation Credential Identification Formats" section immediately below.

  • credential_id (required) -- the individual credential identifier of a credential issued using the issue-credential-v2 protocol that has been revoked by the issuer. Accepted values for the credential id format are provided in the "Revocation Credential Identification Formats" section immediately below.

  • comment (optional) -- a field that provides some human readable information about the revocation notification. This is typically the reason for the revocation as deemed appropriate by the issuer.

Revocation Credential Identification Formats

In order to support multiple credential revocation formats, the following dictates the format of revocation formats and their credential ids. As additional credential revocation formats are determined their credential id formats should be added.

Revocation Format Credential Identifier Format Example
indy-anoncreds <revocation-registry-id>::<credential-revocation-id> AsB27X6KRrJFsqZ3unNAH6:4:AsB27X6KRrJFsqZ3unNAH6:3:cl:48187:default:CL_ACCUM:3b24a9b0-a979-41e0-9964-2292f2b1b7e9::1
anoncreds <revocation-registry-id>::<credential-revocation-id> did:indy:sovrin:5nDyJVP1NrcPAttP3xwMB9/anoncreds/v0/REV_REG_DEF/56495/npdb/TAG1::1

Reference

Drawbacks

If we later added support for more general event subscription and notification message flows, this would be redundant.

Rationale and alternatives

  • Why is this design the best in the space of possible designs? It is simple.
  • What other designs have been considered and what is the rationale for not choosing them? A more general event subscription and notification mechanism was considered but chose to keep this simple for the same reasons that the basic message was kept simple.
  • What is the impact of not doing this? There is no standard way of sending a revocation notification which is a common scenario.

Prior art

Unresolved questions

Implementations

The following lists the implementations (if any) of this RFC. Please do a pull request to add your implementation. If the implementation is open source, include a link to the repo or to the implementation within the repo. Please be consistent in the "Name" field so that a mechanical processing of the RFCs can generate a list of all RFCs supported by an Aries implementation.

Name / Link Implementation Notes