Cryptology ePrint Archive: Report 2002/022

From Identification to Signatures via the Fiat-Shamir Transform: Minimizing Assumptions for Security and Forward-Security

Michel Abdalla and Jee Hea An and Mihir Bellare and Chanathip Namprempre

Abstract: The Fiat-Shamir paradigm for transforming identification schemes into signature schemes has been popular since its introduction because it yields efficient signature schemes, and has been receiving renewed interest of late as the main tool in deriving forward-secure signature schemes. We find minimal (meaning necessary and sufficient) conditions on the identification scheme to ensure security of the signature scheme in the random oracle model, in both the usual and the forward-secure cases. Specifically we show that the signature scheme is secure (resp. forward-secure) against chosen-message attacks in the random oracle model if and only if the underlying identification scheme is secure (resp. forward-secure) against impersonation under passive (i.e.. eavesdropping only) attacks, and has its commitments drawn at random from a large space. An extension is proven incorporating a random seed into the Fiat-Shamir transform so that the commitment space assumption may be removed.

Category / Keywords: public-key cryptography / Signatures, identification, Fiat-Shamir, random oracle model

Publication Info: An extended abstract of this paper appears in the proceedings of EUROCRYPT 2002. This is the full version.

Date: received 24 Feb 2002, last revised 18 May 2007

Contact author: mihir at cs ucsd edu

Available format(s): Postscript (PS) | Compressed Postscript (PS.GZ) | PDF | BibTeX Citation

Version: 20070519:033816 (All versions of this report)

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