Study On Real-time Digital Image Encryption Algorithm Based On Chaos

Digital media has become a primary method for human to attain information asthe development of network and information technology. Mostly, information of thesedigital images transmits via network, it is easy to illegal copy, transfer, stole or falsifythe information by attackers unless safety measures are taken during the transmissionprocess. Therefore, it is important to protect the security and confidentiality of digitalimage information. An upsurge to study the technology of digital image encryption isgrowing up domestic and overseas. As many characteristics of chaos confirm therequirements of cryptography, the image encryption technology based on chaos isemerging as the times require.This paper is mainly based on the application of chaotic theory in the imageencryption. Firstly, the development of image encryption research based on chaos wasintroduced, then the basic theories of chaos and cryptography were expounded, and therelationship between them was analyzed. Two cipher systems were introduced,according to the cipher systems of stream cipher and block cipher, three imageencryption algorithms based on chaotic theory were designed. The first algorithm hasbrought forward a way of image encryption algorithm based on3D Lorenz chaoticsystem according to the safety of image information. This algorithm regards thechaotic sequence and the pixel coordinate of the color image as two points in space,using the formula of the distance of two points in space to generate the sequences toencrypt the image. The single pixel replacement encryption method is vulnerable toknown-plaintext attack, so design image encryption algorithm of combining the pixelscrambling and pixel replacement, firstly it used the chaotic sequences which isgenerated by optimization models of3D Lorenz system, then by using the gravitymodel to scramble the color image, finally utilized chaotic sequences is generated by2D Logistic chaos system to scramble the color image. An algorithm for generating substitution boxes based on the logistic map was presented and a block cipher using S-boxes was proposed, the plaintexts are divided into many blocks, each cipher blockwas obtained by rounds of substitution and the Modulo-Plus function with S-boxes.Results demonstrate that the algorithm in this paper is easy to carry out, the key issensitive to the initial values, the space of key is large enough, and the pixel valuesdistribute uniformly.Finally, this paper summarized the research and indicated its future researchdirections.