System Design And Optimization Of Physical True Random Number Generation Based On Chaotic Lasers

Random numbers are widely used in information security and computing. Random numbers are used in information security schemes as codes, keys and challenges to ensure confidentiality, authenticity and integrity of information. Random numbers are also used for sampling in numerical computations to solve problems in many fields, including materials science, biophysics and finance. Among the traditional generators of random numbers, fast random numbers, generated by computer, are not completely random for the deterministic algorithms. True random numbers can be generated by physical processes, such as electrical noises, frequency jitters in electrical oscillators and chaotic circuits. But they are not suitable for modern high-speed communications for their rates are limited by the narrow bandwidth of these physical entropy sources. The utilization of chaotic sources based on semiconductor lasers with external disturbance can ensure the generation of true random numbers at the rates of Gbit/s and even higher, which can show a potential advantage in the application field of high-speed communication data security and get the height attention of the related scholars and industry players.In order to obtain physical true random numbers with high speed and high quality, this paper uses chaos semiconductor laser as the physical source of true random number generator, experimental researched physical true random number generator at the rates of 640Gbit/s. Meanwhile this paper study the Influence of feedback strength on the characteristics of the random number sequence extracted from an external-cavity feedback semiconductor laser by using theory, the specific research work areas follows:(1) FOR high-speed true random number based on bandwidth enhancement chaotic laser entropy source is realized by experiments investigation. Chaotic laser signal from chaotic source with dual-path injection from a single master laser is divided into two paths after through the photoelectric converter, one path is converted to binary code by 8-bit ADC, the other is converted to binary code after a delay time 8-bit ADC conversion, and the order of 8-bit codes are reversed, eventually the two paths of 8-bit binary code are processed by bit-xor operation to obtain 8-bit binary code random sequence at the rate of 640Gbit/s. The random number sequence is verified by the NIST Special Publication 800-22 tests. In this paper, the system entropy characteristics are investigated by experimental and the mechanism of the post-processing part are investigated by theory, the results show that bandwidth of chaotic laser signal from the dual-path-injected is higher than the bandwidth of chaotic laser signal from single-path optical injection, at the same time the former can better hide external cavity feedback delay characteristics, and in the case of positive frequency detuning effect will be better. In the case of the number of binary code is unchanged, bit-order-reversed xor process can improve the equilibrium of distribution effectively and the true random numbers with high quality and high speed are finally generated.(2)Under proper feedback strength, an external-cavity feedback semiconductor laser can operate at a chaos state, and its chaotic output can be used as a physical entropy source to generate a physical random number sequence. In this paper, we focus on the influence of feedback strength on the randomness of the obtained binary code sequence. The simulation results show that with the increase of feedback strength, the time delay characteristic peak of the chaotic signal from an external-cavity feedback semiconductor laser first decreases and then increases gradually, meanwhile, the permutation entropy characteristic value of chaotic signal first increases and then decreases gradually, namely, there exists an optimized feedback strength for obtaining the chaotic signal with the weakest time delay signature and high complexity. The randomness of binary code sequences, generated by the chaotic signal from the external-cavity feedback semiconductor laser under different feedback strengths, is tested by NIST Special Publication 800-22, and the influence of feedback strength on the test results is also discussed.