Methods to Forge ElGamal Signatures and Determine Secret Key

Abstract

We present a new method to forge ElGamal signatures with the cases that the secret key parameters of the system are not known under the chosen signature messages. The attacker can forge the signature substituting the right signature, and also attack the right secret key without depending on the computation of discrete logarithm. With the attacking probability cryptanalysis, it is found that the cryptosystem can be attacked successfully in some conditions