Research Of Multimedia Information Encryption Based On Coding

Multimedia technology is one of the most popular applications in computer science. Thanks to the wide-spread use of PC and great development of Internet, The demanding for multimedia technology will keep increasing in the next few decades. The multimedia information, especially sensitive information about politics, military affairs or business secret is vulnerable to attack. So how to protect multimedia information has became a hotspot issue.Multimedia content has some special features, such as, large data quantity, high redundancy, low unit value, demanding for real-time processing. It would spend a lot of unnecessary time and compute resource if we use the traditional encryption algorithms. So some special algorithms based on the characteristics of multimedia content were proposed by some scholar. In general, Those encryption algorithms can be classified into three categories. (1) traditional encryption algorithm; (2)selective encryption algorithm; (3)encryption algorithm based on compression. These algorithms have advantages in special areas. This paper analyzes their performance in security, speed, format compliance and so on, then we proposed the multimedia information encryption algorithms based on coding.Multimedia information encryption algorithm based on coding perform encryption in coding process by combining the encryption and coding algorithm together. This kind of algorithms have couples of advangtages such as high speed, high efficiency, and better security performance because of no encryption to the format related data. For every single coding algorithm has its own special data format which is essential to decoding process, The cryptograph must maintain the data format as the same as the plaintext. Therefore, the format compliance is one of the difficulties in algorithm design.The innovation of the paper is that the corresponding multimedia encryption schemes for several popular coding algortithm are proposed.(1) The characteristics of the LZW coding are analyzed. Taking GIF which based on LZW as an example, different selective encryption algorithms are proposed for both degradation and confidentiality models. In degradation model, we propose index mapping within subsets to achieve the image quality controllable, and to keep format compliance. In confidentiality model, we maintain the security by encrypting a small quantity of data. Experiments show that we reach the goal of security and format compliance without any compression ratio decline in both models.(2) The Multimedia encryption algorithm based on multiple Huffman table is crashed by Known-Plaintext Attack according to the analysis of the characteristics of Huffman coding. Then the improved algorithm which base on chaotic system is proposed. And its security and other features are analyzed by experiment.