High-Speed True Random Number Generation Based On Wideband Chaotic Laser Sources

Random numbers have a wide range of applications, such as information security, stochastic modeling and spread spectrum communications. Although a computer can generate fast random numbers based on initial seeds and certain deterministic algorithms, they are in fact not completely random. Truly nondeterministic random numbers can be generated from 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 broadband chaotic laser sources 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.Focusing on the research project of high-speed true random number generation based on wideband chaotic laser sources, this thesis is mainly summarized in the following:1. For high-speed true random number generation based on wideband chaotic laser sources, multiple schemes including Double Chaotic Laser Sources Xor (DCLSX) scheme, Signal Chaotic Laser Source Delay Xor (SCLSDX) scheme and Signal Chaotic Laser Source Difference (SCLSD) scheme are experimentally investigated. In addition, an experimental scheme of robust high-speed true random number generator is proposed and the corresponding random number generator prototype is developed. True random sequences at rates of1.44Gbit/s are generated in real time and pass all of NIST and Diehard tests.2. Many key issues in various high-speed true random number generation schemes based on chaotic laser sources are investigated. In DCLSX scheme, we analyze the dependence of randomness on some important factors, in particular the detection threshold of the comparator, the characteristics of external cavity feedback time-delay, the laser relaxation oscillation frequency and the bandwidth of chaotic laser signals. In SCLSDX scheme, by doing a large number of experiments and theoretically analyzing the interplay between the Run test and the threshold value of the autocorrelation function, we overcome the key issue of how to select a suitable delay length. In the scheme of robust true random number generator based on the differential comparison of chaotic laser signals, we analyze the performance of the differential comparison and the system robustness. 3. The above-mentioned high-speed true random number generation schemes are faced with a common issue, i.e., The directly generated random bit sequence has the periodicity caused by the external cavity of chaotic laser sources. To overcome it, an effective solution is explored from the fundamental point of view. We propose and numerically demonstrate that the feedback induced time-delay characteristics in a chaotic semiconductor laser can be eliminated by randomly modulating feedback phase.4. An image encryption scheme based on the one-time pad encryption mechanism is proposed by utilizing true random numbers extracted from the chaotic laser source as secret keys. The security of the image encryption scheme is analyzed in detail. The experimental results demonstrate that our image encryption scheme provides an efficient and secure way for image data encryption with good statistical characteristics and high key sensitivity.