Generic Construction of (Identity-based) Perfect Concurrent Signatures

The notion of concurrent signatures was recently introduced by Chen, Kudla and Paterson. In concurrent signature schemes, two entities can produce two signatures that are not binding, until one of the parties releases an extra piece of information (namely the keystone). Subsequently, it was noted that the concurrent signature scheme proposed in the seminal paper cannot provide perfect ambiguity. Then, the notion of perfect concurrent signatures was introduced. In this paper, the authors define the notion of IDentity-based (or ID-based) perfect concurrent signature schemes. They provide the first generic construction of (ID-based) perfect concurrent signature schemes from ring signature schemes.