Cryptanalysis on a chaos-based cryptosystem with dynamic key

Abstract

This work performs the cryptanalysis on a chaotic cryptosystem with dynamic key whose position is related to ciphertext (DKPC). The DKPC could be equivalently transformed into a typical structure of permutation-diffusion, where permutation based on breadth-first search is dependent on static key only, while diffusion with dynamic feature is determined by an additional dynamic key of which the location is associated with ciphertext except the static one. The best innovation of DKPC lies in the introduction of dynamic key position to improve the security. However, it has been overestimated and there are still many vulnerabilities after analysis. This paper deciphers the permutation via an innovative approach first. Then the equivalent static and dynamic keys of diffusion are broken respectively by chosen-ciphertext attack. The complexity is much lower than that of cryptanalysis on other plaintext-related algorithms. Theoretical analysis and experimental results indicate that the cryptanalysis is effective and feasible.