Research On The Security Of Several Classic Chaotic Image Cryptosystems

In the age of the rapid development of computer and Internet, network information security has become the common concern in all walks of life. Cryptosystem as the basic techniques for information security has become a research hot in the?eld of security. There are some intrinsic relationship between chaos and traditional cryptography. Chaotic system have many good properties, such as the sensitive dependence on initial conditions and control parameters, ergodicity, the density of the set of all periodic points which are similar to some properties such as avalanche,confusion and di?usion in cryptography. Because of the big di?erence between images and texts, the traditional text encryption algorithms cannot protect images e?ciently. Therefore, many researchers consider chaos as a novel way to design secure and e?cient image cryptosystem. In recent years, researcher proposes a number of chaos-based image encryption algorithms.This dissertation focus on study the security of four classic recently-proposed chaos-based image encryption algorithms, the main achievements and innovations are as follows:1. This dissertation ?nds a property of Chinese Remainder Theory(CRT) on the relationship among the product of some moduli, the divisor corresponding to a special set of remainders, and divisor. Based on the property, the equivalent secret key of CECRT, which proposed by Zhu et al., can be reconstructed e?ciently under the chosen-plaintext attack scenario. The three other defects in terms of e?ciency and safety, including invalid compression function, low sensitivity with respect to change of plaintext, and improper usage of CRT moduli as sub-key,are also discussed.2. A comprehensive analysis on solving a composite function involving carry bit,which is composed of modulo addition and bitwise OR operations, is presented,and the probability of every bit can be con?rmed is discussed. Base on some properties of the function, we ?nd that MCKBA can be broken e?ciently with two known plain-images and the corresponding cipher-images. In addition, it is reported that a previously breaking method, which proposed by Li et al., can be further improved by reducing the number of chosen plain-images to two from four.3. This dissertation re-evaluates the security of an image cipher based on transformed logistic maps and proves that the image encryption algorithm can be deciphered e?ciently under the condition of two known plain-images or two chosen plain-images. In contract, the required condition in the previous deciphering method proposed by Zhang et al. is eighty-seven chosen plain-images. In addition, three other security defects existing in Logistic map based encryption algorithms widely are also reported.4. This dissertation analysis the security of the encryption algorithm based on improved hyperchaotic sequences and ?nds that the encryption algorithm can be broken with only one known plain-image. The performance of the knownplaintext attack, in terms of success probability and computation load, become even much better when two known plain-images are available. In addition, security defects on insensitivity of the encryption result with respect to changes of secret key and plain-image are also reported.