Cryptology ePrint Archive: Report 2018/037

Weakly Secure Equivalence-Class Signatures from Standard Assumptions

Georg Fuchsbauer and Romain Gay

Abstract: Structure-preserving signatures on equivalence classes, or equivalence-class signatures for short (EQS), are signature schemes defined over bilinear groups whose messages are vectors of group elements. Signatures are perfectly randomizable and given a signature on a vector, anyone can derive a signature on any multiple of the vector; EQS thus sign projective equivalence classes. Applications of EQS include the first constant-size anonymous attribute-based credentials, efficient round-optimal blind signatures without random oracles and efficient access-control encryption. To date, the only existing instantiation of EQS is proven secure in the generic-group model. In this work we show that by relaxing the definition of unforgeability, which makes it efficiently verifiable, we can construct EQS from standard assumptions, namely the Matrix-Diffie-Hellman assumptions. We then show that our unforgeability notion is sufficient for most applications.

Category / Keywords: Structure-preserving signatures, security proof, standard assumptions.

Original Publication (in the same form): IACR-PKC-2018

Date: received 8 Jan 2018

Contact author: rgay at di ens fr, Georg Fuchsbauer@ens fr

Available format(s): PDF | BibTeX Citation

Version: 20180108:181538 (All versions of this report)

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