Image Encryption Based On Chaotic System And DNA Sequence

Image encryption is an important mean of protecting the security of image information. But image itself has high redundancy, large amount of information and high correlation between adjacent pixels. Because of these characteristicals, traditional encryption methods are not suitable for image encryption. Owing to the pseudo-random, unpredictable and extreme sensitivity to initial value of chaotic system, these characteristics make chaotic systems satisfy the requirements of Cryptogrphy. However, due to their shortcomings of chaotic systems, the encryption algorthns only using chaotic system is attacked easily. The encryption effect of the image encryption algorithm combined the DNA sequence with the chaotic system performs well in correlation, entroy, etc. But the ability to resist some attack, such as differential attack is not so well. Based on this background, we propose two encryption algorithms. The main results are as follows:An image encryption algorithm based on chaotic system and dynamic S-box composed of DNA sequence was proposed. In this algorithm, a construction method of S-box composed of DNA sequence is designed. In order to resist known-plain attack and chosen-plain attack effectively, two measures was given. One is the S-box is relation with plain image, the other is the chaotic sequence to split DNA sequene is associated with plain image. Diffferent plain images will obtain different chaotic sequences and different S-box through the proposed algorithm. And the encrypted DNA subsequence would affect the construction of DNA S-box. It could resist known-cipher attack. Simulation results show that the proposed algorithm has a good encryption effect, a large key space and high sensitivity to key and plain image.A bit-image encryption algorithm based on hyper-chaos system and DNA sequence was proposed. DNA-bit matrix was proposed. According to the characteristic that DNA located in high positions carries more than 94% information of original image while DNA located in high positions carries less than 6% information, the performance to resist noise attack is enhanced. Simulation results show that this algorithm enhances the ability to resist noise attack and could resist differential attack.