Chaos-based image encryption algorithms are widely investigated recently. Concrete implementation of theses conventional chaos-based algorithms usually arise some security problems due to the computation precision restriction. This paper proposes an improved chaos-based image encryption scheme, in which the grayscale substitution is done by circular bit shift method. The scheme enlarges key space to 2 212 , which improves the security under precision restricted condition. The combination of position permutation and grayscale substitution operation makes the encryption system strong against known/chosen-plaintext attack. The chaotic binary and decimal key streams are proved to have good statistical property. Theoretical analysis and experimental results show that the scheme proposed in this paper is more secure than conventional chaos-based ones.
['Chong Fu', 'Zhiliang Zhu']
A Chaotic Image Encryption Scheme Based on Circular Bit Shift Method