Research On Physical Layer Security Technology Based On Polar Codes

In order to meet the needs of communication applications in the fifth generation mobile communication network(5G),the reliability and security of data has become a key factor in its development.5G puts higher demands on new coding technologies and encryption technologies.In the traditional encrypted communication model,the encryption process is performed on the upper layer.The emergence of supercomputers make the eavesdropper easily intercept the information through the physical layer channel.Therefore,wireless security communication based on physical layer channel characteristics has become a new research direction which is called physical layer security(PLS).In addition,with the evolution of channel coding technology,polar codes has been emplyed in 5G control channel with high reliability.However,channel coding and data encryption scheme are often regarded as two different processes of the communication system,which affect the complexity and delay of data processing.Therefore,the joint design of error correction and encryption at the physical layer can provide a low-complexity and low-latency transmission scheme.Based on the analysis of existing research results and security requirements,this paper conducts research on channel coding technology in PLE,which can be used not only for civil wireless communication systems,but also for military wireless communication systems.This paper mainly makes research on the coding and encryption scheme of the physical layer.The main work and results are as follows:(1)In order to improve the traditional communication model,we implemente encryption while encoding.The key generation technique is used to generate the initial key as the seed of the chaotic generator to generate the chaotic sequence for encryption.The polar codes is adopted and a delay feedback encryption structure is designed.The chain effect can greatly increase the complexity of the eavesdropper decryption degree.The simulation results show that the encrypted ciphertext can pass the randomness test,i.e.,the ciphertext encrypted by the delay feedback has good unpredictability.The algorithm has high security without affecting the performance legitimate communication.(2)For the coding characteristics of the polar codes,i.e.,the frozen bits are used to transmitted the all-0,a PLE algorithm based on the frozen bits is proposed.We use frozen bits to transmit chaotic sequences,which make error correction and encryption be performed simultaneously.Simulation analysis shows that the algorithm ensures the security of the physical laye without affecting the reliability of data transmission.The key sensitivity test results show that the encryption key is highly accurate and has strong key sensitivity.Since the eavesdropper does not know the chaotic sequence in frozen bits,it cannot be correctly decoded.(3)The eavesdropper may perform the same key extraction operation at the location of the legitimate recipient to steal the initial key.Besides,we find that partial frozen bits encryption could chieve same security.Therefore,a physical layer encryption algorithm based on partial frozen bits and AES encryptor is proposed.The chaotic sequence is encrypted by AES encryptor to obtain encryption keys,and encryption keys are placed in the partial frozen bits of polar codes.In the transmission,because of the XOR iteration of the different bits,we could still realize the confidentiality of the system without affecting the communication quality.(4)Aiming at the problem of high peak-to-average power ratio(PAPR)in OFDM systems,a physical layer encryption and PAPR joint scheme is proposed to solve the PAPR problem and achieve high security of the transmission system.The scheme segments the chaotic sequence generated by the key generation and matches the index value,and uses the best information bits of the polar codes to store the index value of the chaotic sequence.Using the SLM idea,the remaining information is encrypted by using the chaotic sequence corresponding to the index value,and the lowest PAPR encryption result is selected for transmission.This scheme not only implements encryption security in the physical layer coding process,but also reduces the PAPR of the OFDM system without increasing system complexity and delay.Finally,I make a summary of the research work.The proposed scheme also improves the security performance of the system without affecting the reliability of the system.It has broad application prospects in the future 5G commercial communication system and military communication system.Combined with the existing physical layer security technology,it is hoped that the future will be further studied for 5G new air interface technology and physical layer security issues in military communications.