Cryptology ePrint Archive: Report 2003/196

Security Analysis of Some Proxy Signatures

Guilin Wang, Feng Bao, Jianying Zhou, and Robert H. Deng

Abstract: A proxy signature scheme allows an entity to delegate his/her signing capability to another entity in such a way that the latter can sign messages on behalf of the former. Such schemes have been suggested for use in a number of applications, particularly in distributed computing where delegation of rights is quite common. Followed by the first schemes introduced by Mambo, Usuda and Okamoto in 1996, a number of new schemes and improvements have been proposed. In this paper, we present a security analysis of four such schemes newly proposed in [15,16]. By successfully identifying several interesting forgery attacks, we show that all the four schemes are insecure. Consequently, the fully distributed proxy scheme in [11] is also insecure since it is based on the (insecure) LKK scheme [14,15]. In addition, we point out the reasons why the security proofs provided in [15] are invalid.

Category / Keywords: public-key cryptography / digital signatures, proxy signatures, security analysis.

Publication Info: Revised version appears in the Proc. of ICISC 2003, LNCS 2971, pp. 305-319. Springer-Verlag, 2004.

Date: received 23 Sep 2003, last revised 11 Apr 2004

Contact author: glwang at i2r a-star edu sg

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Version: 20040412:034253 (All versions of this report)

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