Abstract:

Many of the basic characteristics of the chaotic systems can be linked with the concepts of confusion and diffusion in cryptography, and the chaos theory began to get involved in the cryptography field in the 1980s. As a kind of new cryptography technology, chaotic cipher has become a hot topic in the field of information security in recent years. We study the security of a digital image encryption algorithm, and show that the digital image encryption and decryption algorithm based on Lorenz chaos system is essentially a shift cipher. We also point out the leakage laws of the algorithm and propose a algorithm against known plaintexts attacks. For a  N1×N2 plain image, the computational complexity is (N1×N2)2/212. Theoretical analysis and experimental results demonstrate the insecure feature of this digital image encryption algorithm.

Key words: cryptanalysis;chaos cipher;digital image encryption algorithm;know plain text attack;Lorenz chaotic map