强不可伪造的双向代理重签名方案

Bidirectional Proxy Re-signature Scheme with Strong Unforgeability

在代理重签名中,一个拥有重签名密钥的半可信代理者可以把受托者的签名转换为委托者对同一消息的签名(即重签名),但该代理者不能单独生成受托者或委托者的签名。标准模型下的代理重签名方案多数是存在不可伪造性的,无法阻止敌手对已经签名过的消息重新伪造一个合法的签名。为此,利用基于密钥的目标抗碰撞杂凑函数,提出一种新的双向代理重签名方案。在计算Diffie-Hellman困难问题的假设下,证明该方案在适应性选择消息攻击下是强不可伪造的。分析结果表明,与已有强不可伪造的双向代理重签名方案相比,该方案的系统参数和重签名的长度短,且重签名的计算量小。

In a proxy re-signature scheme,a semi-trusted proxy is allowed to transform a signature from a delegatee into a signature from a delegator on the same message using the re-signature key. But the proxy cannot generate signatures for either the delegatee or the delegator. Proxy re-signature schemes in the standard model are existentially unforgeable,which cannot prevent forgeries from forging valid signatures on new messages not previously re-signed. Based on target collision-resistant hash function,a bidirectional proxy re-signature scheme is proposed. Under computational DiffieHellman assumption,the proposed proxy re-signature scheme is provably secure against strong forgery under adaptive chosen message attacks. Moreover,the new scheme has some advantages over the available schemes,such as short system parameters,short re-signature and low re-signature computation cost.