A Secure Communication Scheme Based On Network Coding And Hash Function

Network coding is first introduced by R.W.Yeung and R.Ahlswede in 2000. Network coding is different from the traditional information processing method ,which is called store-and-forward routing scheme. As a matter of fact, on intermediate nodes, network coding encodes the information of input channels then sends out through output channels. Study shows network coding can increase the network throughput, and achieve the upper bound which is determined by the Max-flow Min-cut theorem. According to the relationship between input and output nodes, the network coding can be divided into linear network coding and non-linear network coding. Consider the Linear network coding which coding simple and fast to implement,so research and application of network coding is mainly based on the linear network coding。In the traditional information transmission process, for some important information we try to improve the security of transmission. Then in the network coding, there also exist security issues. The question is could we combine the special nature of network coding when we try to solve the issues. The answer is absolutely. N.Cai and W.Yeung in the literature [24] proposed a model of the security issues which is called a communication systems on a wiretap network (CSWN), in the literature a necessary and sufficient condition for the feasibility of contructing a secure linear network code is derived, and also give a solution to the issue. Later, based on this approach, there are many methods have been putting forward proposals. For example, utilize the rank distance code to achieve the secure communication. No matter what method to be used, the essence of these methods are based on embedding uniformly distributed random symbols in the information vector and mixing them with information symbols through linear combinations. It has been shown that with existing approaches, the number of noisy symbols must be at least equal to k, if the adversary can assess at most k independent channels. In the case of k larger, these existing approaches in significant reduction in information rate.In order to reduce the number of redundant symbols and improve the efficiency of information transmission M. Adeli, and H. Liu in the reference literature [36] has proposed a scheme that requires only one noisy symbol to be embedded in the original information symbol vector to achieve complete secrecy. This scheme utilizes hash functions to generate different random noisy symbols by using the only uniformly distributed random symbol and the information symbols. The noisy symbol k is very important in this scheme, But in the M. Adeli, and H. Liu scheme, the k can't be protected well, can be easily recovered through linear combination. This thesis try to improve M. Adeli, and H. Liu's scheme. This thesis was organized as follow. In chapter 1, describes the network coding knowledge. In chapter 2, describes the knowledge of secure communication. In chapter 3, introduce the CSWN model, and gives some existing schemes which achieve secure communications. In chapter 4, the main results of this thesis was give,which improve M. Adeli, and H. Liu's scheme. In the last we give a example to illustrate the improved scheme.