A fast image encryption scheme based on chaotic standard map

In recent years, a variety of effective chaos-based image cryptosystems have been proposed. One of the architectures of this kind of cryptosystems is composed of multiple rounds of substitution and diffusion. As the confusion and diffusion effects are solely contributed by the substitution and the diffusion stages, respectively, the required overall rounds of operations in achieving a certain level of security is found more than necessary. In this Letter, we suggest to introduce a certain diffusion effect in the substitution stage by simple sequential add-and-shift operations. Although this leads to a longer processing time in a single round, the overall encryption time is reduced as fewer rounds are required. Simulation results show that at a similar performance level, the proposed cryptosystem needs less than one-third the encryption time of an existing fast cryptosystem. The effective acceleration of chaos-based image cryptosystems is thus achieved.