Cryptology ePrint Archive: Report 2003/068

On the Security of Some Proxy Signature Schemes

Hung-Min Sun and Bin-Tsan Hsieh

Abstract: Digital signature scheme is an important research topic in cryptography. An ordinary digital signature scheme allows a signer to create signatures of documents and the generated signatures can be verified by any person. A proxy signature scheme, a variation of ordinary digital signature scheme, enables a proxy signer to sign messages on behalf of the original signer. To be used in different applications, many proxy signatures were proposed. In this paper, we review Lee et al.'s strong proxy signature scheme, multi-proxy signature scheme, and its application to a secure mobile agent, Shum and Wei's privacy protected strong proxy signature scheme, and Park and Lee's nominative proxy signature scheme, and show that all these proxy signature schemes are insecure against the original signer's forgery. In other words, these schemes do not possess the unforgeability property which is a desired security requirement for a proxy signature scheme.

Category / Keywords: Cryptanalysis, Digital Signature

Date: received 11 Apr 2003, last revised 6 May 2003

Contact author: hmsun at cs nthu edu tw

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

Note: We note the general form of original singer's forgery.

Version: 20030506:135100 (All versions of this report)

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