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  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  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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