A block chaotic image encryption scheme based on self-adaptive modelling

• Self-adaptive error is added in the initial conditions in every round, of which shows the novelty of this manuscript.
• A rule is designed to let errors be positive or negative. A new control parameter is generated dependent on errors, it is also self-adaptive.
• Only diffusion function is applied, but it can reach a high security and less time cost.
• The keystream depends on the plain-image which can resist efficiently the known-plaintext and chosen-plaintext attacks.
• UACI (unified average changing intensity) and NPCR (number of pixels change rate) results confirm that the proposed method can reach the ideal effect.

In this paper, we suggest a block image encryption algorithm which can give us an efficient scheme to hide and encrypt image data. Only the diffusion function, instead of classical permutation plus diffusion operations, is adopted. The plain-image is firstly divided into two equal parts randomly by vertical, horizontal, or diagonal directions. Then encryption of one part depends on the other part, in which the keystream is generated by the plain-image, i.e., one of the two parts. An error concept is added in the initial conditions in every round. It means that the keystreams are different in the process of encryption steps. The error may be positive or negative decided by a rule of sign function. Experiment results show that the proposed method can provide a high security of cryptosystem, and can reduce the computation redundancy compared with that of the traditional architectures such as Arnold map based method, and totally shuffling based method.

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