Research Of Image Encryption Algorithm Based On Time-delay Feedback Chaotic System

With the rapid development and widely application of the Internet and the computer multimedia technology, image has already become an important means of information storage and transmission,while the security of the image information has faced a huge challenge. Therefore, how to protect the security of the image information has become a hot research issue at present.Encryption technology is an important method to assure the information security, but now widely used of the traditional encryption technology is mostly based on the protecting text, there is few encryption schemes proposed for image encryption according to image features. However, the traditional encryption schemes have many flaws, such as low efficiency and weak security. So aimed at the image information's intrinsic features, this article raise an image encryption algorithm based on time-delay chaos combining chaos widely researched and traditional encryption technologies.Firstly, the significance of image encryption and present state are introduced in this article,basic knowledge of cryptography, present encryption mechanism and cipher analysis are generalized.Secondly, chaotic system theory is introduced; developing process of chaos theory, chaotic characteristics, chaos criterion and some other basic theories are depicted in detail.Moreover, several typical chaotic systems are given in this article, time-delay feedback Lorenz chaotic system and its chaotic attractor's evolution process are explained detailedly. Based on deep understanding of digital image encryption and chaotic theory, an image encryption algorithm based on time-delay feedback Lorenz chaotic system is proposed.This scheme consists of three parts, including initial permutation, image pixels transformation and Arnold mapping transformation. The key space of this algorithm as well as key sensitivity, plain-text image sensitivity, plain histogram, cipher histogram and so on is simulated and analyzed. The consequences show that the algorithm proposed has good permutation effectiveness, can encrypt and decrypt image effectively and that there is no distortion in decryption process.At the meanwhile, this scheme has some definite capabilities of anti-statistic attack, anti-chosen plaintext attack and anti-noise, and it has preferable stability.