LAUSR

Recently, Behzad et al. designed a 1-D chaotic coupled Sine map (CCSM) and a dynamic scrambling process based on the size of blocks and then constructed an image encryption algorithm (CSMIE) based on CCSM and the scrambling method. However, we find that the algorithm cannot be used for secure communication because it cannot resist chosen-plaintext attacks. In this paper, we first analyze the real structure of CCSM generated in a digital computer with limited precision and then propose a chosen-plaintext attack to break CSMIE according to the number of blocks. Moreover, we enhance CSMIE by designing a synchronous scrambling and diffusion mechanism which utilizes a three-dimensional hyper-chaotic system and employs the hash values of the plain-image. A series of simulation experiments are conducted to evaluate our enhanced encryption scheme. The experimental results demonstrate that the enhanced encryption scheme performs well in various test indicators and can resist the chosen-plaintext attack.