On the ElGamal-Like Cryptosystems for Encrypting Large Messages

摘要

To encrypt large messages over wide area networks, both key distribution protocol and block cipher encryption are necessary. Usually, people employ the technique of hybrid cryptosystem to achieve the goal by using one public-key cryptosystem for session key distribution, then using a conventional block cipher for bulk encryption. Recently, an ElGamal-like public-key based cryptosystem for encrypting large messages was proposed. In this paper, we consider some fundamental security issues and potential weakness of the ElGamal-like cryptosystem, and we also consider how to enhance the design to have better security and performance of such ElGamal-like public-key based cryptosystem for encrypting large messages. We also point out the applicability of such pure public-key based cryptosystem for implementations in small devices.