Abstract: This paper finds that in improved Perfect Concurrent Signature(iPCS), the signer can bind multiple messages with one Keystone but let the other signers know only one of the messages, which is unfair for signers. The accountability of Concurrent Signature(CS) is proposed and defined, and an attack case which breaks the accountability in one scheme of Perfect Concurrent Signature(PCS) and an update version of the perfect concurrent signature are proposed, in which the Keystone transfer function takes the exchanged message and Keystone as the input parameters to realize the binding between Keystone and messages. The scheme satisfies the accountability of CS.

Key words: fair exchange, Concurrent Signature(CS), Perfect Concurrent Signature(PCS), accountability

摘要： 指出在改进的完美并发签名方案中，签名方可将多个待签名消息绑定在同一个Keystone上，只让其他签名方知道其中一个消息，该情况对于各签名方是不公平的。提出并定义完美并发签名的可追踪性，给出一个针对完美并发签名方案可追踪性的攻击实例及对应的修订方案，待签名消息与Keystone一起作为Keystone transfer函数的输入参数，实现了签名消息与Keystone的唯一绑定，使修订后的方案满足可追究性要求。

关键词: 公平交换, 并发签名, 完美并发签名, 可追踪性

CLC Number: 

• TP309.2