| With the development of the network technology, people are now transporting more andmore information from the Internet. While enjoying the convenience brought by the Internet,we also start to take attention about information security. Especially which involved inmilitary, medical and personal privacy. The image data is the most important one of theinformation that transported on line. How to make sure the data’s security has become veryurgent.Firstly, it gave a brief description of the development, current situation, developmenttrend, and the practical significance of the digital image encryption. A new image encryptionalgorithm was proposed according to the chaos system’s pseudo-randomness, initialsensitivity, uncertainties and the problems as well as the image encryption based on chaosexists the chaotic characteristics degradation and low-dimensional chaotic system is used forencryption easy to be cracked. The algorithm combined with the one-dimensional map,two-dimensional Logistic map and higher-dimensional chaos, it can effectively overcomethese problems. The encryption cracking experiment, anti-cut attack experiment and anti-noseattack experiment were organized to prove the algorithm has high key space, uniformdistribution of the ciphertext and encryption didn’t have periodic. It can resistant theexhaustive attack, the correlation of adjacent pixel was close to zero, it also can change theimage‘s histogram. According to the color image’s characteristics the algorithm was used toencrypt the different color components. it can ensure that tiny movements of the componentswill be spread to the entire color components.With the combination of the algorithm and the DCT transform to encrypt the space andthe frequency of the image, it increased the complexity of the algorithm and overcame theproblem of encrypting the image only in the space. In the frequency the algorithm scrambledthe image in the unit of block. After the inverse transform, the first encrypted image wasobtained, and then, by the encryption of the space of it to obtain the finally ciphertext. Sincethe DCT transform has been widely used in the image compression, it has some theoreticalsignificance for combination of compression and encryption of the image. By the experimentsof several attacks, the calculation and the simulation of the adjacent pixels correlation of theimages in former and latter, the result of the experiment and the simulation showed the good effect of this algorithm. The ciphertext evenly distributed, and the encryption does not haveperiodic. The key space is large, the decrypted image and the original image has a goodconsistency. If decryption only in the space, it won’t get the right plaintext. |
