Cryptanalysis of image scrambling based on chaotic sequences and Vigenere cipher

Recently, an image scrambling scheme based on chaos theory and VigenSre cipher was proposed. The scrambling process is firstly to shift each pixel by sorting a chaotic sequence as VigenSre cipher, and then the pixel positions are shuffled by sorting another chaotic sequence. In this study, we analyze the security weakness of this scheme. By applying the combination of chosen-plaintext attack and differential attack, we propose two efficient cryptanalysis methods. Results show that all the keystream can be revealed. The original image scrambling scheme can be remedied by leveraging the MD5 hash value of the plain image as the initial condition of the chaotic system.