Improvement on a Signed ElGamal Encryption

改善簽章型式ElGamal加密技術的效率

Previously, two schemes were proposed to enhance the security of ElGamal encryption. The weakness of the original scheme is improved by adding a message authentication tag to ciphertext. The resultant schemes are non-malleable encryption under chosen ciphertext attack. We observed that the same security goal can be achieved with less computational cost. The proposed scheme saves 33% of computing power on average. In processing decryption, it can save at most 46% of computations if the technique of multiple simultaneous exponentiations is used.