Attacks on a Universal Designated Verifier Signature Scheme

In literature, two new universal designated verifier signature proof schemes (UDVSP) based on hardness assumption of the discrete-logarithm problem were proposed at Asiacrypt \´05. The UDVSP scheme were proven secure against impersonation attacks in random oracle under type-1 attack and type-2 attack. Unfortunately, these schemes are totally breakable by any attacker if the attacker is allowed to interact concurrently with many different prover "instances" as well as with the verifier (concurrent reset attacks for short). In this paper, the UDVSP schemes are shown insecure against impersonation under type-1 attack and are also proven transferable, which contradicts the design goal of universal designated verifier signature scheme.