Research On Physical Layer Key Distribution Technology Based On Channel Phase Response

It is a security method based on the physical layer to use the uniqueness and the reciprocity of wireless channel to realize key distribution. Regarding the characteristics of wireless channel as random signal source, taking measures on channel of legitimate users to get the similar key sequence, and eliminating the inconsistence of key sequence by key agreement and confidentiality enhanced technology, and finally gets the uniform key. But these methods have three problems as follows: First, low quantization precision leads to the lack of security of key distribution. Second, uniformization method requires multiple rounds of communication and high computational complexity. Third, the resulting low key distribution rate significantly limits their practical application when the channel vibrates slowly. To overcome the above limitations, this paper is supported by National Natural Science Foundation Project, and researches on the physical layer key distribution technology which is based on channel phase response.Firstly, to overcome low quantization precision leads to the lack of security of key distribution, an approach of key distribution based on the channel difference is proposed. Secondly, to overcome uniformization method requires multiple rounds of communication and high computational complexity, an approach of key distribution based on combining Trellis Coded Modulation(TCM) coding with encryption of channel phase response is proposed. Finally, to overcome the resulting low key distribution rate significantly limits their practical application when the channel vibrates slowly, a novel cooperative key distribution method based on phase estimation is proposed. The main contents are as follows:1. This paper presents an approach of key distribution based on the channel difference. Firstly, in the single-input single-output system model, the ergodic safe transmission rate of the key is achieved via transforming the channel between legitimate users channel and eavesdropper channel into phase rotating and additive noise channels’ cascade. Secondly, extracting the key by using the channel phase difference of legitimate users and eavesdropper can ensure the security of key distribution. Meanwhile, key space could be broadened by increase the extraction accuracy of channel phase response, which is converted into key length. Finally, approaching key capacity by continuous key distribution strategy, and taking binary source as an example to explain the method. The simulation result indicates that when the estimation error of received signal is 0.001, the bit error rate rises to 0.5 rapidly.2. A novel approach is proposed to implement key distribution based on combining TCM coding with encryption of channel phase response. Firstly, after the random-generated key sequence is coded by TCM, the encoded key information with redundancy will be achieved. The sender conceals the encoded key information using security sequence to get parity information which is transmitted to the receiver publicly. Secondly, receiver recovers the key information from parity information using security sequence. Meanwhile, receiver corrects the inconsistency of the security sequence in two ends which facilitates the use of redundancy in key information and finally gets the uniform key. The simulation result indicates that when the estimation error of received signal is 0.0001, this method has near 5dB gain than the conventional methods.3. A novel cooperative key distribution method based on phase estimation is proposed. Firstly, the paper constructs a cooperative relay key distribution model. Secondly, the key nodes and relay nodes send each other tone signal of zero initial phase to conduct channel estimation, we explicitly consider the effect of maximum likelihood estimation(MLE) method on the extraction of key bits from the underlying fading channels, and equal interval quantizing the estimated information. Finally, the relay nodes send quantized information to the key nodes, to obtain consistent key between key nodes, it uses the key agreement method which is based on Trellis Coded Modulation. Simulation results show that, the key rate of the cooperative key generation as the number of relay nodes increases. The key rate is 1500bits/s when the relay nodes are 5.