Symmetric Chaos-Based Image Encryption Technique on Image Bit-Planes using SHA-256

With development of communication technology, popularity of internet and various facilities like cloud storage, social media etc., the security of transmitted data has become an area on concern. Majority of the data is in the form of multimedia which can be protected through various encryption techniques. In this paper, we propose an encryption technique for images which is hybrid of Lorentz attractor and Secure Hash Algorithm (SHA-2) applied on separated bit planes of the image. Our research utilize the chaotic nature of the Lorenz attractor and has significantly improved the entropy, which is an important parameter to measure the randomness. We also introduce a new method of implementing chaotic scheme. SHA-2 and Lorentz attractor are used to generate the key matrix. Bit-plane slicing is carried out on the plain image to decompose it to 1- D data and then X-OR operation with the key matrix is performed. The encrypted file is subjected to various analysis and attacks. The results demonstrate that the algorithm is resistant to various known attacks along with desirable security performance. Both encryption and decryption in the proposed algorithm are loss less. The proposed algorithm shows significant increase in Entropy, improved differential attack analysis results, desirable histogram and are comparable with the state of the art algorithms.