Improving an Image Encryption Scheme Based on Chaotic Signals with Finite-Precision Error

Recently, an image encryption scheme with new chaotic signals has been proposed. Some limitations of this scheme will be pointed out. It adopts a “diffusion–permutation” architecture. The diffusion encryption is linear and can be simplified. Bit-level permutation significantly decreases the encryption efficiency. To solve the above problems, an improved scheme is proposed. The new scheme employs a Feistel-like network with four rounds of encryption. The dynamic substitution box (S-box) generated by Fisher–Yates permutation increases the nonlinearity of encryption. The optimized diffusion process is applied to obtain the avalanche effect. The experimental results show that the improved scheme performs well. In addition, the resistance against various attacks is analyzed from the perspective of a cryptanalyst.