Long-Haul Correlated Random Bit Generation Using Electro-Optic Chaotic Entropy Source Based On Analog-Digital Hybrid Feedback Loop

Correlated random number generator is the crucial component for high-speed one-timepad confidential communication systems.The security of confidential systems relies on randomness provided by entropy sources,which means a malicious adversary would be confused about the correspondence between plain and cipher message.Currently,pseudo random number generators on basis of deterministic algorithms are widely employed,which,unfortunately,could only offer limited randomness,and the upcoming leap of computing power would become a great threat.True random number generators usually take advantage of physical phenomena,thus are also referred to as physical random number generators.Both noise and chaos are such kinds of physical phenomena,or termed as entropy sources,from which high-quality random number could be derived.A distinguished scheme among them is chaotic laser.Its inherent broad band and capability to synchronize make itself a promising candidate to produce high-speed correlated random number.Recent proposals focus on realizing synchronization through analog optical driving signal,which is prone to channel characteristics.Therefore,the range of synchronization is limited.By comparison,digital signal can overcome the deficiency and reach such goal.The dissertation adopts an electro-optic chaotic entropy source based on analog-digital hybrid feedback loop,combining both analog and digital parts together.On one hand,digital signal is converted to analog waveform with broad band and high dynamic complexity.On the other,new digits are obtained from the waveform with key parameters kept safe.The remote terminal responds accordingly to the same digits to regenerate the identical waveform.Furthermore,procedure of random bit extraction as well as post processing happens at both ends.The main contribution of the dissertation includes:(1)Proposal on theoretical model of the electro-optic chaotic entropy source based on analog-digital hybrid feedback loop.The analog part transforms digital signal to analog waveform,whose amplitude oscillates over time through phase modulation to intensity modulation conversion.The digital part samples and quantizes the waveform,conducts nonlinear transformation in digital domain to generate new digits,and transmits them to the analog part.(2)Analysis over the dynamic characteristic of the chaotic entropy source.Through autocorrelation function,permutation entropy,maximal Lyapunov exponent and some other methods,quantitative analysis is practiced while proceeding numerical simulation and practical experiment.The effects of different device parameters and algorithm settings are investigated.(3)Generation of correlated random number after long-haul chaotic entropy source synchronization is realized.Effects on the signal regeneration performance of device parameter detuning at varying degrees are studied.The feasibility of chaotic entropy source synchronization over 100 and 200 km is substantiated.Correlated random number is obtained by both direct and dual-threshold decision methods.(4)The randomness of random number is evaluated.The results of NIST SP 800-22 statistical test suite shows that random number originated from the proposed generator has passed all sub-tests after post processing.