Ursa is a cryptographic library for use with blockchains. The revocation schema that is part of the Ursa CL-Signatures implementations has a flaw that could impact the privacy guarantees defined by the AnonCreds verifiable credential model, allowing a malicious holder of a revoked credential to generate a valid Non-Revocation Proof for that credential as part of an AnonCreds presentation. A verifier may verify a credential from a holder as being "not revoked" when in fact, the holder's credential has been revoked. Ursa has moved to end-of-life status and no fix is expected.
| Package (Ecosystem) | Introduced | Fixed | Limit |
|---|---|---|---|
| ursa(crates.io) | 0 | N/A | N/A |
| anoncreds-clsignatures(crates.io) | 0 | N/A | N/A |
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