Image encryption algorithm with an avalanche effect based on a six-dimensional discrete chaotic system

Abstract

This paper introduces a six-dimensional discrete chaotic systems (SDDCS) with some simple sine functions and a chaotic pseudorandom number generator (CPRNG) that is designed based on the SDDCS. A encryption scheme with both key avalanche effect and plaintext avalanche effect (SESKPAE) is proposed by using the random sequence generated by the CPRNG. The algorithm has three advantages: First, the initial values of the chaotic system are calculated by using the SHA-256 hash value of the plain image and the given values, there are different initial values for different plain images. Thus, our algorithm can resist against the chosen-plaintext and known-plaintext attacks effectively. Second, the new algorithm adopts ciphertext feedback mechanism to further strengthen the safety. Third, our new algorithm has an “avalanche effect”, in other words, the decrypted ciphertext will become a “white” image with a few “black spots” rather than a random chaotic image as a result of the wrong key. The experimental results and security analysis show that the algorithm has the advantages of large key space, no obvious statistical characteristics of ciphertext, sensitive to plaintext and keys, and able to resist chosen-plaintext attack and active attacks.