Hierarchical Bit-Level Image Encryption Based on Chaotic Map and Feistel Network

Abstract

In this paper, to avoid chosen-plaintext attacks and to enhance the security, SHA-256 hash value of the plain image is introduced to produce the initial values and parameters of the chaotic system, thus the produced keys and the ciphered image are highly sensitive to changes of the plain image. Based on the plain image related chaotic sequences, a hierarchical bit-level image encryption scheme is proposed by using an “Incomplete” Feistel network. In this scheme, the left four most significant bits (MSB) and the right four least significant bits (LSB) of each pixel are encrypted differently by the “Incomplete” Feistel network. During the encryption process, different bitplanes of gray image and color image are encrypted differently by the keystreams generated from the Logistic-Sine system (LSS) and the Lorenz system. The theoretical analysis and experiment results show that the proposed encryption algorithm is effective and secure enough to be used for image encryption.