Cryptology ePrint Archive: Report 2008/098

On Security Notions for Verifiable Encrypted Signature

Xu-An Wang and Xiaoyuan Yang and Yiliang Han

Abstract: First we revisit three - BGLS, MBGLS and GZZ verifiably encrypted signature schemes[2,3,6].We find that they are all not strong unforgeable.We remark that the notion of existential unforgeable is not sufficient for fair exchange protocols in most circumstances.So we propose three new - NBGLS, MBGLS and NGZZ verifiably encrypted signature schemes which are strong unforgeable. Also we reconsider other two - ZSS and CA verifiably encrypted signature schemes[4,8], we find that they both cannot resist replacing public key attack. So we strongly suggest that strong unforgeable for verifiably encrypted signature maybe a better notion than existential unforgeable and checking adjudicator knowing its private key is a necessary step for secure verifiably encrypted signature scheme.

Category / Keywords: public-key cryptography /

Date: received 3 Mar 2008, last revised 21 May 2008

Contact author: wangxahq at yahoo com cn

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Version: 20080521:113037 (All versions of this report)

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