Identity-based signatures are the groundwork of many cryptographic protocols. This paper analyzed GU KE et al. 's ( GU KE, JIA WEIJIA, JIANG CHUNLIANG. Efficient and secure identity-based signature scheme. Journal of Software, 2011,22(6): 1350 - 1360) efficient identity-based signature scheme. Two equivalent signature generating algorithms were proposed and it was pointed out that Gu et al. 's scheme could not satisfy the basic security properties. In other words, any attacker could use the equivalent secret key and signature generating algorithms proposed in this paper to forge a valid secret key of a user and a valid signature on any message with respect to any identity in their scheme. Furthermore, the reason that the scheme is insecure was also analyzed and it was pointed out that designing a more efficient identity-based signature scheme than the classical one is almost impossible.%基于身份的签名方案是许多密码协议的基础.通过对谷科等(谷科,贾维嘉,姜春林.高效安全的基于身份的签名方案.软件学报,2011,22(6):1350-1360)提出的基于身份的高效签名方案进行分析,提出了两种等价的签名生成算法,指出该方案不满足基于身份签名方案的基本安全性质.分析表明,任何攻击者都可以利用所提出的等价的私钥和签名生成算法来伪造任意用户的私钥以及任何用户对任意消息的有效签名.同时也分析了原方案不安全的原因,并指出设计比经典方案更加高效的基于身份签名方案是几乎不可能的.
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