Abstract We provide evidence that the unforgeability of several discrete-log based signatures like Schnorr signatures cannot be equivalent to the discrete log problem in the standard model. This contradicts in nature well-known proofs standing in weakened proof methodologies, in particular proofs employing various formulations of the Forking Lemma in the random oracle Model. Our impossibility proofs apply to many discrete-log-based signatures like ElGamal signatures and their extensions, DSA, ECDSA and KCDSA as well as standard generalizations of these, and even RSA-based signatures like GQ. We stress that our work sheds more light on the provable (in)security of popular signature schemes but does not explicitly lead to actual attacks on these.
Paillier and Vergnaud REF showed that the security of Schnorr signatures cannot be based on the difficulty of the one more discrete logarithm problem in the standard model.
Discrete-Log-Based Signatures May Not Be Equivalent to Discrete Log
ASIACRYPT
Computer Science