Cryptanalysis and Improvement of an Efficient CCA Secure PKE Scheme

Recently in Chinese Journal of Computers, Kanget al. proposed an efficient CCA secure public key encryption (PKE) scheme, and claimed that it is more efficient in the public/private keys than the famous CS98 and BMW05 CCA secure public key encryption scheme. However, in this paper we will show that their proposal is not secure at all. Furthermore, we improve their scheme to be a secure one and prove its security.