High Speed Key Distribution Based On Broadband Chaotic Signal

With the rapid development of communication technology and constant growth of transmission rate,the secure transmission of information is becoming more and more important in current research.As one of the key technologies of secure communication,secure key distribution between legitimate users has received extensive attention.The current secure communication systems mainly use the key distribution schemes based on encryption algorithm,which security is mainly determined by the complexity of the algorithm.However,with the emergence of quantum computing,this kind of scheme can be cracked.As a theoretical secure key distribution scheme,quantum key distribution still exits gaps with current communication systems in terms of transmission rate and communication distance.Chaotic laser has important research value in the field of key distribution due to its dynamic characteristics.However,in the field of key distribution,the relaxation oscillation and time-delay signature of the chaotic laser limit the key distribution rate and the security of schemes.Therefore,aiming at the shortcomings of chaotic lasers,this thesis conducts research on high-speed key distribution based on broadband chaotic signals by optimizing chaotic entropy sources.The research works are as follows:1.In this thesis,a secure key distribution scheme based on spectrum spreading VCSELs is proposed,which chaotic synchronization is achieved by using the injection of same chaotic laser.The Spread-Spectrum-Module is used to generate synchronized broadband chaotic signal as the physical entropy source.The result shows that the bandwidth of chaotic signal is significantly enhanced by spectrum spreading,and the TDS of signals can be effectively suppressed.The robustness of the scheme is studied by discussing the synchronization quality of chaotic signal and the BER of key in the condition of laser parameters are mismatched and the injection laser passes through an asymmetric channel.Eavesdropper cannot recover the key from the signal intercepted on the public channel.In addition,the security of the scheme can be further enhanced by adding random number generators on the legitimate users to control the feedback delay of the laser independently,which introducing dynamic chaos synchronization into the system.Lastly,the theoretical key distribution rate in the scheme is studied and the final key can pass the randomness test.2.In this thesis,a high-speed key distribution scheme based on multi-channel broadband chaotic signals is proposed.The scheme increases the number of entropy sources in the system by performing linear differential processing on chaotic signals in the post-processing.The bandwidth of the chaotic signals generated by linear processor is above 20 GHz and the TDS of signals can be effectively suppressed.The chaotic entropy sources in the system can simultaneously achieve chaos synchronization with large injection intensity.The robustness of the system is studied by discussing the synchronization quality of chaotic entropy source and the corresponding BER of key under the laser parameter mismatch.The security of the system is demonstrated from a variety of perspectives,such as the low correlation between different entropy sources and the suppression effect of the TDS.In this scheme,the theoretical key distribution rate can reach 36 Gbps and can pass the randomness test.3.Combining the optical OFDM communication technology,a high-speed key distribution and information integrated transmission scheme is proposed.Through simulation,the transmission performance of the scheme in the condition of different fiber channel length and OSNR is studied.By introducing eavesdroppers into the OFDM secure communication system,it is verified that the encryption/decryption algorithm in the scheme can guarantee the safe of information transmission and has little influence on the communication performance of the system.