Research On Secret Key Generation And Application In Physical Layer Based On Private Pilot

Secret key generation(SKG)in physical layer is a technology where the legitimate users use the randomness,reciprocity,diversity and time variability to generate shared secret keys.Compared with the classic encryption schemes,SKG based on wireless fading channels has the attractive features of lightweight,universality,information-theoretic security,and obtains the “one time pad” perfect security named by Shannon.Therefore,SKG in physical layer shows tremendous potential in withstanding the passive and active attacks,and has gained considerable attention in recent years.Currently,SKG is mainly focused on how to improve the SKG rate(SKGR)and secret key capacity(SKC)under passive eavesdropping,where the legitimate users use the no correlation between the legal channels and the eavesdropping channels to generate secret key according to the channel impulse response(CIR),the received signals strength(RSS)and the phase,time-delay,envelope and so on.However,the broadcast and openness of the transmission medium make the wireless communication attractive to the eavesdropping,replaying and tampering attacks.Under the active attacks,how to secure and quickly generate the shared secret keys in physical layer for the legitimate users is facing severe challenge: firstly,the openness and invariance of the public pilot provide the active attackers an opportunity to implement replaying and tampering attacks to SKG;secondly,how to securely generate the shared secret keys based on the wireless channels for the legitimate users under the active attacks;thirdly,how to generate secret keys and encrypt the data for the resource constrained devices in physical layer.Aiming at the above problems,supported by National 863 project program and the National Natural Science programs,this paper firstly explores the damages of the man-in-the-middle attack by transparent forwarding the channel-training signals to the SKG based on wireless channels;secondly,the legitimate users generate dynamically private pilots to fight against the active attack;then,the legitimate users generate secret keys using the generated private pilot in fast and static wireless channel environments under active attacks;finally,the legitimate users encrypt the date using the generated secret keys in physical layer for the resource constrained devices.The main research results are as follows:1.The private-pilot generation for physical layer SKG.To address the problem of high information leakage rate(ILR)using public pilot to estimate wireless channel under active attacks,this paper proposes the private pilot generation approach according to the private information of identities and location.Firstly,the man-in-the-middle(MITM)attack is introduced into SKG based on wireless channels,where the attacker transparent forwards the channel training signals to control the channel measure,intercept the channel information and derive the generated secret key.Research finds that the attack can intercept all channel information passing through it.To fight against this attack,the paper uses the private information of identities and location to generate dynamically private pilot.The generated private pilot has some characters as follows: 1)the private pilot can encrypts and authenticates the wireless channels between the legitimate users;2)the private pilot can make the intercepted information decrease to zero when its inner product is always constant;3)the private pilot can make the channel estimation error satisfied the minimum mean square error;4)the SKGR is almost equal to the SKGR without eavesdropping and attack.Theoretical analysis and simulation results show that the MITM attack is a severe threat to the SKG based on wireless channels,and the generated private pilot can withstand the MITM attack effectively.2.The SKG using dynamically private pilot under fast fading wireless channels.To the problem that different active attack is withstood with the responding measure,this paper explores the SKG using the dynamic private pilot.During the SKG based on wireless channel,the private pilot is updated with different channel parameters,which guarantees the security and dynamic state of the private pilot,and realizes the channel-training and channel-estimation with different private pilot each time.Then,the SKG is researched and the closed-solution of SKGR is given under two different scenarios,where there exist available paths or no available paths between the legitimate users.Finally,the SKG based on wireless channel researched under active attacks from the MITM attack to passive eavesdropping,impersonation attack and signals injecting attack.Theoretical analysis and simulation results indicate that the SKG scheme using private pilot can not only withstand passive eavesdropping,MITM attack,impersonation attack and signals injecting attack,but also make the SKGR close to the SKGR without the above attacks.3.Fast SKG and channel authentication using private pilot and singular value decomposition in static or quasi-static wireless channel environments(SWCE).For the problem that the SKGR is very low in SWCE under active attack,this papper presents the SKG scheme using private pilot and singular value decomposition(SVD).In static or quasi-static wireless channel environments,during the wireless channels are encrypted with private pilot,the legitimate users reconstruct the wireless channel to improve the randomness and rate of the SKG.The process of the reconstructing channels are described as: firstly,the legitimate users do SVD to the wireless channels estimated with private pilot;then,they generate random diagonal-matrix,reconstruct the wireless channel and modulate the transmitted signals with the reconstructing channel;finally,the legitimate users generate secret keys using the equivalent channel or the received signals.Meanwhile,since the invariability or slow variability of the wireless channel,the legitimate users can authenticate the wireless channel by comparing the two adjacent channel estimation values or using the left and right eigenvector matrixes of the wireless channel.Theoretical analysis and simulation results present that the SKG scheme using private pilot and singular value decomposition can not only enhance the randomness and rate of the SKG,but also fight against passive eavesdropping,MITM attack,impersonation attack and signals injecting attack.4.Lightweight encryption using the generated secret keys based private pilot in physical layer.Aiming to the problem that it is difficult for the resource constrained devices to encrypt using traditional encryption method,this paper proposes physical layer light encryption method using compressed sensing.The process of lightweight encryption is described as follows: firstly,the secret keys generated in physical layer are taken as seed of the Linear Feedback Shift Register(LFSR)to generate m-sequence,which is turned into the sensing matrixes of Bernoulli and Gaussian.Then,the transmitted signals are encrypted during they are compressed with the generated sensing matrix.The sensing matrixes are shared by the legitimate users because of the symmetry of the generated secret keys.With the sensing matrix and received signals,the legitimate user can recover the original transmitted signals by the compressed sensing technology.The attacker cannot obtain the original transmitted signals without the generated secret key or the sensing matrix.Theoretical analysis and simulation results indicate that although the compressed sensing technology cannot obtain the information-theoretic security,it can acquire the computational security against the active attack to secret keys and sensing matrix.