高效的不可否认的门限代理签名新方案

基于Kim等人的门限代理签名方案,Sun提出了已知签名人的不可否认的门限代理签名方案。在Sun的方案中,代理签名人不能否认他们所进行的代理签名。随后,Hsu等人证明Sun方案不能抵抗共谋攻击,并提出了相应的改进方案。论文首先证明了Hsu等人的改进方案不能抵抗公钥替换的内部攻击,即任何恶意的内部攻击者,不需要其他代理签名人的密钥,对任意的消息能够伪造一个有效的门限代理签名。然后提出了一种不可否认的门限代理签名新方案,能同时抵抗内部的公钥替换攻击和共谋攻击。就计算复杂度和通信成本而言,该文的方案比Hsu等人的方案更有效、更实用。

New Efficient Nonrepudiable Threshold Proxy Signature Scheme

Based on Kim et al.'s threshold proxy signature scheme,Sun proposed a nonrepudiable threshold proxy signature scheme with known signers.In Sun's scheme,actual proxy signers cannot deny the signature they have signed.Recently,Hsu et al.explained that Sun's scheme is vulnerable against the conspiracy attack,and proposed an improved scheme that can withstand the conspiracy attack.In this paper we show that their improved scheme is insecure against insider's public-key substitution attack.Any malicious insider attacker without any secret keys of the other signers can forge a valid proxy signature for any messages.Then,we present a new nonrepudiable threshold proxy signature scheme that can withstand both the insider's public-key substitution attack and the conspiracy attack.Furthermore,the presented scheme is more efficient than Hsu et al.'s in terms of computational complexities and communication costs.