Multimedia Information Security And Encryption Algorithm

With the development of communication, signal and information processing technology, encryption thchnology, the key to protect information security, has already attracted more and more attention.Multimedia has become great favorite in communication, as a result of its excellent characteristics of intuition and efficiency. But, in some applicaton fields, such as political, economical and military affairs, etc., sensitive multimedia is transmitted by public channel or storaged in public data base. Which makes it face threaten of wire tapping or tamper. So, multimedia information encryption becomes more and more important. Usually, multimedia is of generous data, needing high speed in encryption or decryption, going with coding and decoding during transmitted or storaged. This makes traditional encryption algorithms restricted, when applied to multimedia. Therefore, new encryption algorithms fit for multimedia are deadly desiderated.From the point of view of information security, this thesis investigates new algorithms for multimedia encryption and decryption, based on recent theoretical result of chaos and neural network in nonlinear dynamics.Firstly, cryptology and related theory is summarized. Especially, multimedia encryption algorithms are classified and their characteristics are studied in detail.Secondly, surveying on the state of the art, a modified method to create streaming cipher based on spatiotemporal chaos is proposed. After tested performance, this cipher is used to encrypt image data. The result shows that this method has a stronger secret performance than the streaming cipher based on low-dimensional chaotic maps, and it is simple to be realized.Thirdly, a new method to construct one-way HASH function based on CNN (Chaotic Nerual Netwok) is proposed. Experiment result obtained from text data shows that the HASH function based on CNN has advantages of sensitivity to initial values and user key, irreversibility and weak collision.In the end, a selective encryption scheme based on sensitive data detect is proposed, aiming at characteristics of multimedia. Then, experiment on audio data has been done, which result shows that this scheme has advantages of resisting attack, high security and speediness.