## Cryptology ePrint Archive: Report 2002/167

Cryptanalysis of Two New Signature Schemes

Fangguo Zhang and Kwangjo Kim

Abstract: Group signature and blind signature are very important primitives in cryptography. A group signature scheme allows a group member to sign messages anonymously on behalf of the group and a blind signature scheme can ensure anonymity of the sender of a message. Recently, S. Xia and J. You proposed a group signature scheme with strong separability in which the revocation manager can work without the involvement of the membership manager and J.J-R. Chen and A.P. Chen proposed a blind signature scheme based on dual complexities (which combines factorization and discrete logarithm problem). In this paper, we give a universal forgery attack on Xia-You's group signature scheme which any one (not necessarily a group member) can produce a valid group signature on an arbitrary message, and it is untraceable by the group revocation manager. For Chen-Chen's blind signature scheme, we show that it could not meet the untraceability property of a blind signature, $i.e.$, it could not ensure anonymity of the user.

Category / Keywords: Group signature, Blind signature, Cryptanalysis

Date: received 8 Nov 2002

Contact author: zhfg at icu ac kr

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

Short URL: ia.cr/2002/167

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