A Novel Plaintext-Related Image Encryption Algorithm Based on Stochastic Signal Insertion and Block Swapping

Image encryption is an important method for protecting private data during communication. This paper proposes a novel hyperchaotic image encryption algorithm based on stochastic signal insertion and block permutation. First, the 5D hyperchaotic system is applied to generate pseudorandom number sequences. The SHA-256 hash function and secret keys are used to produce the initial values of the cryptosystem. The hash values can effectively enhance the sensitivity to plain image. To enlarge the key space and change orbit of cryptosystem, some stochastic signals are inserted during iteration. The plain image is equally divided into two parts. An X-coordinate, a Y-coordinate and a control table are established with produced pseudonumber sequences. The pixel is swapped with another pixel in the current block or another block depending on the control table. Cyclic shift is performed during the diffusion process. Performance and security analyses are executed to verify the effect of the proposed scheme. It is clear that the proposed scheme has a large key space and is highly sensitive to plain image and secret keys. Moreover, the cryptosystem has low computation complexity and can resist correlation analysis, entropy analysis, statistical attack, differential attack, noise and data loss attacks.