Research On The Technology And Protocol Of Secret Key Generation In MIMO Channel

Wireless channel is vulnerable to security threats,such as interference and eavesdropping,due to the inherent nature of openness and broadcast.Currently,the security of mobile communication mainly depends on traditional encryption schemes,which are assessed in terms of security of password and computational complexity.However,due to the lack of a key management infrastructure in mobile scenarios,the distribution and management of keys will be a significant challenge for the security of wireless mobile network.An alternative way for achieving security at physical layer can be implemented by exploiting the inherent properties of wireless channel: reciprocity,temporal variations and spatial variations,which makes the wireless secret key be generated online instead of allocation and the randomness is much higher than the fixed key.In this thesis,we primarily study on the secret key generation technology and protocol in MIMO channel,the main work and contributions of this thesis are described as follows:(1)Physical layer key extraction based on wireless channel characteristics,there is possible inconsistency between the original two keys generated by both legitimate parties.Concerning this issue,firstly,with the reference to the setting of guard-band in channel quantization with guard-band(CQG),an improved adaptive channel quantization with guard-band(ACQG)is proposed.The method corrects the channel measurements which fall into the guard-band through the correction information which interacts by public channels.Compared with CQG method,which discards the channel measurements falling into the guard-band directly,the ACQG method ensures the effective use of channel measurements.Extensive simulation results show that the improved method can extract more secret keys with a low bit disagreement ratio.Secondly,the difference between the partial channel measurements of both sides may be too large to be corrected by the setting of guard-band due to the influence of noise and other factors.Therefore,this thesis further proposes a modified adaptive channel quantization(MACQ)method,which discards the design of guard-band and corrects all channel measurements adaptively.The simulation results show that the MACQ method can further reduces bit disagreement ratio of generated keys.(2)The multiple sub-channels of MIMO are used to improving the key generation rate.However,the correlation between antennas may affect the randomness of keys extracted from characteristics of sub-channels.Aiming at the problem,firstly,an improved antenna selection method based on inter-antenna correlation is proposed,which will be called “Improved Correlation Based Method”(ICBM)in the remainder of this thesis.Compared with the correlation based method(CBM),the improved method selects the antenna according to the overall correlation between the antenna to be selected and the remaining subset of the antennas.By reselecting the transmit/receive antennas,the improved method chooses the sub-antenna array with the lowest overall correlation for communication.Extensive simulation results show that the improved method not only reduces the complexity of the system,but also reduces the correlation between the antennas and solves the problem of inner-correlation between generated keys which are extracted from the characteristics of wireless channels.Secondly,a key generation protocol in MIMO channel is designed in this thesis,which improves the key generation rate by exploiting MIMO,and the generated keys can pass the randomness test.