Research On Wireless Key Generation Technologies In OFDM Communication System

Due to the open nature of radio propagation,wireless communication systems are vulnerable to attacks such as eavesdropping,jamming,and tampering.Currently,most of the communication systems are mainly computationally secure and cannot resist quantum attacks.More and more researchers are turning to study communication systems with information-theoretic security.Information-theoretic security,also known as unconditional security,is a security condition based on strict mathematical theories that cannot be attacked even if the attacker has unlimited computational resources.Communication systems based on wireless channel secret keys have information-theoretic security,and the use of such technology can completely resolve the security problems during data transmission.However,such technology still faces the following challenges.(1)The existing wireless channel secret key generation technology employs the received signal strength and channel impulse response amplitude as the random source,which suffers the limitation of the dimension of the random source and high correlation of channel parameters in a short period of time,resulting in low key generation rate.(2)The communication parties communicate several times in the process of information reconciliation,which will leak the reconciliation information to the eavesdropper,resulting in insufficient key length.(3)The existing research mainly focuses on the theoretical aspects of key generation and lacks practical implmentatoin.1.To address the first issue,this thesis improves the index modulation based key generation method and proposes a key generation scheme SIKG(Subcarrier Index based Key Generation Scheme)for wireless channel key generation.SIKG,in addition to quantizing the secret key bits from the channel impulse response,it also extends the dimension of the random source by employing the index of the subcarrier as a new reciprocal channel parameter.Compared with the traditional key generation algorithm and the joint key generation algorithm,the key generation rate of SIKG is improved by 100% and 33.3%,respectively.2.To address the second issue,a secure pilot scheme BSPS(Block-based Secure Pilot Scheme)is proposed for the information reconciliation scenario.BSPS inserts obfuscated symbols into the subcarriers,which can reduce the possibility of eavesdroppers in detecting the data transmission subcarriers.Simulation experiments show that the upper bound of the reconciliation capacity is improved by 50%.3.To address the third issue,we implement an OFDM secure communication system based on wireless channel keys.The implementation of the system are described in detail,in-cluding: the design and implementation of the time synchronization module,the physical layer frame structure,the algorithm for channel estimation and compensation,the algorithm for frequency shift estimation and compensation,the encryption and decryption module.The source code of the system is fully opensourced.