Paper 2024/958

Signer Revocability for Threshold Ring Signatures

Abstract

t-out-of-n threshold ring signature (TRS) is a type of anonymous signature designed for t signers to jointly sign a message while hiding their identities among n parties that include themselves. However, can TRS address those needs if one of the signers wants to revoke his signature or, additively, sign separately later? Can non-signers be revoked without compromising anonymity? Previous research has only discussed opposing situations. The present study introduces a novel property for TRS- revocability- addressing the need for improved flexibility and privacy security in TRS. Our proposed revocable threshold ring signature (RTRS) scheme is innovative in several ways: (1) It allows a signer to non-interactively revoke their identity and update the signature from t-out-of-n to t − 1-out-of-n; (2) It is possible to reduce the ring size and clip non-signers along with revoked signers while maintaining the anonymity level. We analyze and define the boundaries for these operations and implement and evaluate our structure. With a sufficiently large ring size, we can optimize the signature size, resulting in better signing performance as compared to the extensible signature scheme.