Research On Secret Key Extraction Of Physical Layer In Wireless Communications

Wireless communication technology has been widely used for its convenience. But broadcastnature of Wireless communication leading to security problems have become increasinglyprominent. Meanwhile, the uniqueness of channel characteristics of the wireless communication,reciprocity, rapid time-varying and unpredictable nature, provides the conditions to solve theinformation security of wireless communications. Therefore, the use of wireless communicationphysical layer channel’s attributes to security encryption has become an important research topic.It is an important step to use physical characteristics of wireless communication channal togenerate a random key to ensure information security. In a wireless communication system based ontime division duplex (TDD), using the reciprocity of the wireless channel, both sides independentlyextract key, avoiding the interaction key and preventing the key to leakage. Use channelcharacteristics of time-varying, dynamic updating key, to achieve "one-time pad" to ensurecommunication security. However, there are the following aspects in practical applications.There isa certain bias to estimate the channel for both sides, resulting in inconsistent generated key；the keygeneration rate is not high and the consistency of the key generation rate is mutual with key presenc.Focus of the existing is to study impact of communications security with passive eavesdropping,while the presence of active interference, and the existing system does not work well. Keynegotiation mechanism is not perfect, thus there is a risk of key compromise in the key negotiationinteractive process.For the above deficiencies of the existing key generation model, we propose some improvedmethods. Details are as follows:(1) The use of physical layer attributes to key generation exits the problems that rate is not highand generated key is inconsistent for the presence of encryption for wireless communications. Sowe propose a phase-based algorithm with CQG. Using CQG method, the establishment of the bufferzone at the boundary of the received values deleteing greater probability of false of generated keys,effectively improve the consistency of generated key.(2) We study the game problem of key generation rate with consistency of generated key. Ensuringthe consistency of the premise, the secret key rate is analyzed theoretically. Research results showthat the consistency of generated key are determined by the bandwidth and the modulation order.Bump of function which is decided by the bandwidth and the modulation order is the optimal balance of the key generation rate and consistency.(3) Existing focus is to study the passive eavesdropping security implications for communication.Existing system does not work well with the presence of active interference problems. We propose atwo-slot binary-array coherent interference cancellation method, minimizing the number of thereceiving array element and effectively reducing the computational complexity. While usingprinciple of the signal is uncorrelated with interference, interference cancellation is performed.(4) For key negotiation mechanism is not perfect, there is the risk of key disclosure issues in thekey negotiation interactive process. We propose a "violent attack" key interaction methods, whichone of the parties that has stronger computing ability try to crack the key. It is an effective solutionto the inconsistency of the key problems.