USRP Based Secret Key Generation Using Wireless Physical Layer Characteristics

With the development of communication,wireless mobile communication has advantages of flexibility,convenience.It has a wide influence on people's daily lives.Compared with wired communication,wireless communication with its nature of broadcast is more vulnerable to malicious third-party attacks.Traditional technology of communication security is based on the principle of modern cryptography,which makes use of complex mathematical calculations,stream ciphers and block ciphers for encryption.The continuous development of computing technology brings big problems for traditional security technologies,since it lacks of sufficient proof for their security mechanism.Meanwhile,the security of wireless communication attracts much more researchers.The policy of physical layer security for wireless communication mainly includes two parts,the algorithm based on channel eigenvalue and the advanced algorithm based on channel modulation:The nature of channel is used to extract the eigenvalues and to generate keys,which are in differentity and space-time uniqueness.It does not need to distribute such keys.Because the security of channel does not relays on keys but the randomness of channel.On the other hand,the advanced algorithm of channel modulation depends on information theory.In this theory,the transmission security can be guaranteed by higher channel gain of the main channel and lower of wiretap channel.Then,the security capacity of wireless physical layer will be improved.With the development of multi-antenna multi-path technology,the physical layer security has broader prospects.It will provide a good service for researches on physical layer security with the thought of software wireless processing channel modulation and hardware doing the carrier modulation.Therefore,the main contents in this paper are as follows:(1)This paper provides a research idea of wireless physical layer security.There are two aspects of it: channel characteristics and signal modulation.Channel modulation technology is based on information theory.Its main thought is to improve the legitimate channel signal of noise ratio but to reduce the signal-to-noise ratio of eavesdropping,aiming at the secrecy transmission rate of channel close to secrecy capacity.Channel modulation technology is subject to the development of hardware technology,and this paper does not only analyze the development of OFDM and 5G but also illustrate the prospect of multi-carrier modulation technology.(2)The thought of using software for signal modulation and hardware for carrier modulation in software radio platform is very consistent with the developments of signal modulation technology and hardware equipment.This paper introduces the GNU Radio and USRP software radio platforms,which are useful to realize two aspects of physical layer security come true.One is signal send and signal receive through OFDM,and the other one is extraction of channel feature and key agreement(3)Key generation algorithm based OFDM multi-carrier channel is achieved by software radio platform.This paper obtains the higher peak power average ratio through analysis and comparison of experiment.It also finds that the interference of adjacent carrier frequency will affect the key generation.In order to make full use of the channel characteristics in the time domain and frequency domain of multi-carrier modulation technology and to improve the key generation rate,a key generation algorithm based on self-random frequency hopping is proposed.Moreover,this paper does tests on the key generation rate and randomness of the algorithm by radio platform experiment.