Cryptology ePrint Archive: Report 2012/068

Extended Security Arguments for (Ring) Signature Schemes

Sidi Mohamed El Yousfi Alaoui, zgr Dagdelen, Pascal Vron, David Galindo, and Pierre-Louis Cayrel

Abstract: The well-known forking lemma by Pointcheval and Stern has been used to prove the security of the so-called generic signature schemes. These signature schemes are obtained via the Fiat-Shamir transform from three-pass identi cation schemes. A number of fi ve-pass identi fication protocols have been proposed in the last few years. Extending the forking lemma and the Fiat-Shamir transform would allow to obtain new signature schemes since, unfortunately, these newly proposed schemes fall outside the original framework. In this paper, we provide an extension of the forking lemma in order to assess the security of what we call n-generic signature schemes. These include signature schemes that are derived from certain (2n + 1)-pass identi cation schemes. We thus obtain a generic methodology for proving the security of a number of signature schemes derived from recently published ve-pass identi cation protocols, and eventually for (2n+1)-pass identi cation schemes to come. Finally, we propose a similar extension of the forking lemma for ring signatures originally proposed by Herranz and Sez.

Category / Keywords: public-key cryptography / (ring) signature scheme, forking lemma, security proof, canonical identi cation scheme.

Publication Info: In submission

Date: received 16 Feb 2012, last revised 24 Feb 2012

Contact author: elyousfi at cased de

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Version: 20120224:092734 (All versions of this report)

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