Image Encryption Using Random Bit Sequence Based on Chaotic Maps

The paper proposes an algorithm for image encryption using the random bit sequence generator and based on chaotic maps. Chaotic Logistic and Tent maps are used to generate required random bit sequences. Pixels of the plain image are permuted using these chaotic functions, and then the image is partitioned into eight bit map planes. In each plane, bits are permuted and substituted according to random bit and random number matrices; these matrices are the products of those functions. The pixels and bit maps permutation stage are based on a chaotic random Ergodic matrix. This chaotic encryption method produces encrypted image whose performance is evaluated using chi-square test, correlation coefficient, number of pixel of change rate (NPCR), unified average changing intensity (UACI), and key space. The histogram of encrypted image is approximated by a uniform distribution with low chi-square factor. Horizontal, vertical, and diagonal correlation coefficients of two adjacent pixels of encrypted image are calculated. These factors are improved compared to other proposed methods. The NPCR and UACI values of encrypted image are also calculated. The result shows that a swift change in the original image will cause a significant change in the ciphered image. Total key space for the proposed method is (2^2, 160), which is large enough to protect the proposed encryption image against any brute-force attack.