Research On Cooperative Key Extraction Based On The Channel Characteristics

Because of the broadcasting characteristics of wireless channel, its security is always a contentious issue. Most of the existing solutions are based on some mathematical problems which are hard to solve. In principle, all of them can be broken by trying the possible keys in sequence. This thesis focuses on information theory based security, i.e. unconditional security. In information theory based security, we can assume that adversaries have the infinite time and computing power, and the cryptographic systems will not be broken down even fi the adversaries can try all the possible keys in sequence in a short time. With the development of quantum computers, computing power will be improved significantly. Therefore, it is significant for us to focus our attention on the research of information theory based security.At early time, the researches on unconditional security are always focused on theoretical aspects. Recently, especially after introducing the reciprocity of wireless channel into unconditional security systems, more and more researchers turned to research on the implementation of unconditional security systems. Using the reciprocity of wireless channel to enhance the security is always a hot academic research topic. Mathur[8] has implemented the key extraction test on the 802.11 platform after hardware modification, but it shows a low bit rate. Our research is an improvement to this design. Using the cooperative communication technology for reference, we introduce a cooperative node into the key extraction system to raise the bit rate.The thesis introduce the basic idea of information theory and unconditional security, with the focus on the existing key extraction design schemes, and point out its design deficiencies and tweaks. Then, give out the key extraction design scheme with cooperative node. The whole scheme consists of three parts: cooperative exploring, quantification and agreement on error bits, and key fusion. We point out the new problems because of the cooperative node and possible reference solutions at first, and then propose the details of our scheme. The thesis gives out the test results, which prove that the introducing of cooperative node could increase secret bit rate significantly. At last, we do the performance evaluation on three parts: probability of error, secret bit rate and randomness of generated bits.