Cryptanalysis and Improvement of a Color Image Encryption Scheme Based on DNA Sequences and Multiple 1D Chaotic Maps

摘要

This paper presents cryptanalysis of a color image encryption scheme. DNA encoding and multiple 1D chaotic maps are used in the encryption process which increases its computational speed. The key streams generated in this scheme are dependent on secret keys, updated using the sum of pixel intensities of plain image of size W x H x 3. This paper analyzes the security of encryption scheme against the chosen plaintext attack and finds that only O(768 WH) different key matrices for diffusion are possible, an equivalent version of which can be revealed with O(768 WH) chosen plain images. Experimental results are presented to prove that equivalent diffusion keys and block permutation sequence can be effectively revealed through the attack. In addition, low sensitivity of keys towards changes in plaintext along with insecure diffusion process involved in encryption process is also reported. Finally, to remedy the shortcomings of the original encryption scheme, an enhanced encryption scheme is generated that can resist chosen/known plaintext attack while maintaining the merits of the original encryption scheme.