Image Encryption Based on Hash Table Scrambling and DNA Substitution

This paper proposes an image encryption algorithm based on hash table structure scrambling and DNA substitution. The algorithm uses the classical `scrambling-diffusion' process, and the pseudo-random sequence used in each process is generated by the hyper-chaotic Chen system. Firstly, in the process of scrambling, two sequences with no repeated values are constructed by using the closed hash method in the hash table structure for chaotic sequences, and the plain image is scrambled twice according to the two sequences. Then, in the process of diffusion, DNA coding and decoding rules and DNA substitution rules are made according to the chaotic sequences. The image is dynamically encoded, substituted and decoded with DNA. In this way, while modifying the gray value of image pixels, it also destroys the strong correlation between adjacent pixels. Through a series of verifications, it is concluded that the algorithm not only has good encryption effect, high security and large key space, but also has the advantages of high key sensitivity and strong anti-attack capability.