Research On Chaotic Image Encryption Algorithm Based On DSP Technology

With rapid development of multimedia and the Internet, digital imageshave been increasingly common and popular and the issue of imageinformation security has attracted a great deal of concern. For its ownproperties such as big size and high redundancy, the traditionalencryption algorithms are no longer suitable for image encryption. Recentyears, lots of methods dedicated to image encryption have been proposed.Some of them, however, have disadvantages, for quite part of them can beattacked and deciphered. So the study of image encryption algorithms hasfar-reaching consequence theoretically and in practice.In this thesis, several main aspects have been done:①Cryptanalysis of image encryption algorithms is one of the keyissues. Chosen-plaintext attack is used to attack the hyperchaos-basedimage encryption algorithm. After plaintext and its cipher text known,the details of attacking is presented; and the key as well, which meansthat the algorithm has been deciphered. It proves that this algorithmcannot resist chosen-plaintext attack and that improving its security isnecessary.②The algorithm improved is proposed in which there are two step---permutation and propagation---to encrypt images. With the key generatedby a hyper-chaos system and improved Chebyshev chaotic system and largekey space and high sensitivity of initial values, this new method hashigher security. Simulation demonstrates that this algorithm has highsecurity and is able to be used for encrypting colorful images of any size.The new algorithm is realized through DSP. The SIMULINK mode is firstpresented. Its code is generated by the Real-time Workshop in MATLAB. Andthen the generated code is downloaded in the DSP to realize this algorithm.③At last the digital plain-image is encrypted with DSP. After decryption, the decrypted image is the same with the original,demonstrating that the way to realize the algorithm is practical.In the last part of the thesis, the consequence is made.