IMAGE ENCRYPTION BY APPLYING SECURE HASH SHA-256: A REVIEW PAPER

Abstract

A new image encryption algorithm based on chaos and SHA-256 is proposed in this paper in order to resolve the complexity of key management in "one-time pad" encryption systems and also resist the assault of selected plaintext. It adopts the structure of uncertainty and diffusion. First, to ensure that each encrypted result is different, the environment of a plaintext image is surrounded by a sequence created from the SHA-256 hash value of the plaintext. Secondly, by adding the disruption term associated with the plaintext to the chaotic sequence, the image is scrambled according to the random sequence obtained. Third, in the diffusion stage, the cypher text (plaintext) feedback mechanism of the dynamic index is adopted, i.e., the cypher text (plaintext) position index used for feedback is dynamic. In the "one time pad" encryption scheme, the above steps can ensure that the algorithm can avoid selected plaintext attacks and can resolve the complexity of key management