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
binding, until an extra piece of information (namely the
) is released by one of the parties. Subsequently, it was noted that the concurrent signature scheme proposed in the seminal paper cannot provide perfect ambiguity. Then, the notion of
concurrent signatures was introduced. In this paper, we define the notion of
. We provide the
generic construction of (ID-based) perfect concurrent signature schemes from ring signature schemes. Using the proposed framework, we give two concrete ID-based perfect concurrent signature schemes based on two major paradigms of ID-based ring signature schemes. Security proofs are based on the random oracle model.