A secure proxy signcryption scheme based on discrete logarithm problem

A proxy signcryption scheme is useful for applications particularly in distributed computing such as mobile agent applications and mobile communications. In this paper, we first define the security requirements for proxy signcryption scheme. Then we identify the security weaknesses of the proxy signcryption scheme proposed by Gamage, Leiwo, and Zheng. After that, we improve the signcryption scheme proposed by Wang, Bao, Ma, and Chen. Based on the improved scheme, we would like to propose a new proxy signcryption scheme so that all desired security properties are satisfied without a secure channel.