Deducibility constraints and blind signatures

Deducibility constraints represent in a symbolic way the infinite set of possible executions of a finite protocol. Solving a deducibility constraint amounts to finding all possible ways of filling the gaps in a proof. For finite local inference systems, there is an algorithm that reduces any deducibility constraint to a finite set of solved forms. This allows one to decide any trace security property of cryptographic protocols.We investigate here the case of infinite local inference systems, through the case study of blind signatures. We show that, in this case again, any deducibility constraint can be reduced to finitely many solved forms (hence we can decide trace security properties). We sketch also another example to which the same method can be applied.