Cryptology ePrint Archive: Report 2021/351

Practical Dynamic Group Signatures Without Knowledge Extractors

Hyoseung Kim and Olivier Sanders and Michel Abdalla and Jong Hwan Park

Abstract: Dynamic group signature (DGS) allows a user to generate a signature on behalf of a group, while preserving anonymity. Although many existing DGS schemes have been proposed in the random oracle model for achieving efficiency, their security proofs require knowledge extractors that cause loose security reductions. In this paper, we first propose a new practical DGS scheme whose security can be proven without knowledge extractors in the random oracle model. Moreover, our scheme can also be proven in the strong security model where an adversary is allowed to generate group managersí keys maliciously. The efficiency of our scheme is comparable to existing secure DGS schemes in the random oracle model using knowledge extractors. The security of our scheme is based on a new complexity assumption that is obtained by generalizing the Pointcheval-Sanders (PS) assumption. Although our generalized PS (GPS) assumption is interactive, we prove that, under the symmetric discrete logarithm (SDL) assumption, the new GPS assumption holds in the algebraic group model.

Category / Keywords: public-key cryptography / Algebraic Group Model, Group Signatures, Knowledge Extractors, PS assumption, Random Oracle Model, Subverted CRS

Date: received 17 Mar 2021, last revised 26 May 2021

Contact author: hyoseung_kim at korea ac kr, jhpark at smu ac kr

Available format(s): PDF | BibTeX Citation

Version: 20210527:021106 (All versions of this report)

Short URL: ia.cr/2021/351


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