True random numbers with high security originate from non-deterministic physical processes. Random laser with random feedback arising from multiple elastic scattering in a highly disordered structure is an ideal physical entropy source theoretically. In this work, a secure optical ultrafast random number generator based on random laser spectra was demonstrated. Unlike the usual method of recording laser intensity over time, the random laser spectrum under each pump pulse was recorded and converted into random numbers through post-processing. Approaches in three different dimensions—space, spectrum and time were used to increase the rate of random number generation. The randomness of resulting random bit streams was verified by the NIST statistics tests. Experimental results showed that an instantaneous bit rate of 810 terabits per second with off-line post-processing could be theoretically reached with an ideal experimental condition. This novel technique has big advantages in secure communications and promises to further increase the speed of random number generators to the lever of petabits per second or even higher.
True random numbers with high security originate from non-deterministic physical processes. Random laser with random feedback arising from multiple elastic scattering in a highly disordered structure is an ideal physical entropy source theoretically. In this work, a secure optical ultrafast random number generator based on random laser spectra was demonstrated. Unlike the usual method of recording laser intensity over time, the random laser spectrum under each pump pulse was recorded and converted into random numbers through post-processing. Approaches in three different dimensions—space, spectrum and time were used to increase the rate of random number generation. The randomness of resulting random bit streams was verified by the NIST statistics tests. Experimental results showed that an instantaneous bit rate of 810 terabits per second with off-line post-processing could be theoretically reached with an ideal experimental condition. This novel technique has big advantages in secure communications and promises to further increase the speed of random number generators to the lever of petabits per second or even higher.
Random numbers have great application value in the fields of secure communications, which are commonly used as secret keys to encrypt the information. To guarantee that the information is absolutely secure in the current high-speed communication, the applied random keys should possess a generation speed not less than the encrypted data rate, according to one-time pad theory found by Shannon (Shannon C E 1949 Bell.Syst.Tech.J. 28 656) Pseudo-random numbers generated by algorithm may easily reach a fast speed, but a certain periodicity makes them difficult to meet the aforementioned demand of information security. Utilizing physical stochastic phenomena can provide reliable random numbers, called physical random number generators (RNGs). However, limited by the bandwidth of the conventional physical sources such as electronic noise, frequency jitter of oscillator and quantum randomness, the traditional physical RNG has a generation speed at a level of Mb/s typically. Therefore, real-time and ultrafast physical random number generation is urgently required from the view of absolute security for high-speed communication today. With the advent of wideband photonic entropy sources, in recent years lots of schemes for high-speed random number generation are proposed. Among them, chaotic laser has received great attention due to its ultra-wide bandwidth and large random fluctuation of intensity. The real-time speed of physical RNG based on chaotic laser is now limited under 5 Gb/s, although the reported RNG claims that an ultrafast speed of Tb/s is possible in theory. The main issues that restrict the real-time speed of RNG based on chaotic laser are from two aspects. The first aspect is electrical jitter bottleneck confronted by the electrical analog-to-digital converter (ADC). Specifically, most of the methods of extracting random numbers are first to convert the chaotic laser into an electrical signal by a photo-detector, then use an electrical ADC driven by radio frequency (RF) clock to sample and quantify the chaotic signal in electronic domain. Unfortunately, the response rate of ADC is below Gb/s restricted by the aperture jitter (several picoseconds) of RF clock in the sample and hold circuit. The second aspect comes from the complex post-processes, which are fundamental in current RNG techniques to realize a good randomness. The strict synchronization among post-processing components (e.g., XOR gates, memory buffers, high-order difference) is controlled by an RF clock. Similarly, it is also an insurmountable obstacle to achieve an accurate synchronization due to the electronic jitter of the RF clock. In this paper, we propose a method of ultrafast multi-bit physical RNG based on chaotic laser without any post-process. In this method, a train of optical pulses generated by a GHz mode-locked laser with low temporal jitter at a level of fs is used as an optical sampling clock. The chaotic laser is sampled in the optical domain through a low switching energy and high-linearity terahertz optical asymmetric demultiplexer (TOAD) sampler, which is a fiber loop with an asymmetrical nonlinear semiconductor optical amplifier. Then, the peak amplitude of each sampled chaotic pulse is digitized by a multi-bit comparator (i.e., a multi-bit ADC without sample and hold circuit) and converted into random numbers directly. Specifically, a proof-of-principle experiment is executed to demonstrate the aforementioned proposed method. In this experiment, an optical feedback chaotic laser is used, which has a bandwidth of 6 GHz. Through setting a sampling rate to be 5 GSa/s and selecting 4 LSBs outputs of the 8-bit comparator, 20 Gb/s (=5 GSa/s4 LSBs) physical random number sequences are obtained. Considering the ultrafast response rate of TOAD sampler, the speed of random numbers generated by this method has the potential to reach several hundreds of Gb/s as long as the used chaotic laser has a sufficient bandwidth.
A simple novel method for random number generation is presented, based on a random Raman fiber laser. This laser is built in a half-open cavity scheme, closed on one side by a narrow-linewidth 100 mm fiber Bragg grating. The interaction between the randomly excited lasing modes of this laser, in addition to nonlinear effects such as modulation instability, allow the generation of random bits at rates of up to 540 Gbps with minimal post processing. Evaluation of the resulting bit streams' randomness by the NIST statistical test suite highlights the importance of evaluating the physical entropy content, as bit sequences generated by this random laser pass all the statistical tests with a significance level of 0.01, despite being generated at more than twice the theoretical entropy generation speed.
We demonstrate for the first time, to the best of our knowledge, a high-speed physical random bit generator at gigabits/second without the time-delay signature based on chaotic power fluctuations of a random fiber laser. The random fiber laser is configured using a ring structure with semiconductor optical amplifiers as the optical gain and a fiber random grating as the random feedback medium. The long-length ring cavity provides a large number of densely spaced cavity modes that co-exist within the gain bandwidth tailored by the optical filter. Unlike fixed cavity modes in conventional fiber ring lasers, these modes are less phase-correlated due to the random distributed feedback from the fiber random grating fabricated by a plane-by-plane inscription technique without phase control, leading to intensified lasing output fluctuations with high-dimensional chaotic dynamic natures without specific cavity features, when the random fiber laser is operated slightly above the lasing threshold. Random bit generation at a bit rate up to ∼1.6 Gbps is achieved with verified randomness through standard tests. Different from the previously reported schemes requiring offline post-processing procedures, this physical random number generator can function in real time, offering high-quality randomness and security assurance for pertinent applications.
Random numbers are widely used for information security, cryptography, stochastic modeling, and quantum simulations. Key technical challenges for physical random number generation are speed and scalability. We demonstrate a method for ultrafast generation of hundreds of random bit streams in parallel with a single laser diode. Spatiotemporal interference of many lasing modes in a specially designed cavity is introduced as a scheme for greatly accelerated random bit generation. Spontaneous emission, caused by quantum fluctuations, produces stochastic noise that makes the bit streams unpredictable. We achieve a total bit rate of 250 terabits per second with off-line postprocessing, which is more than two orders of magnitude higher than the current postprocessing record. Our approach is robust, compact, and energy-efficient, with potential applications in secure communication and high-performance computation.
Absolutely secure communication should be implemented only through the ‘one-time pad' proposed by Shannon, requires that physical random numbers with rates matched with the associated communication systems be used as secret keys. With the wide application of the WDM technology in optical communication, the single channel rate of the current digital communication system has exceeded 10 Gb/s and developed towards 100 Gb/s. To ensure the absolute security of such a large capacity communication, a large number of real-time, and secure random numbers are needed.#br#Secure random numbers are commonly produced through utilizing physical random phenomena, called physical random number generators. However, conventional physical random number generators are limited by the low bandwidth of the applied entropy sources such as thermal noise, photon-counting and chaotic electrical circuits, and thus have typical low bit rates of the order of Mb/s.#br#In recent years, chaotic lasers attracted wide attention due to their generation of secure, reliable and high-speed random number sequences, and so due to their coherent merits such as high bandwidth, large amplitude fluctuation and ease of integration. There have been lots of schemes based on laser chaos for high-speed random number generation, but most of them execute the random number extractions from the associated laser chaos in the electrical domain and thus their generation rates are faced with the well-known ‘electrical bottleneck'. On the other hand, all-optical random number generation (AO-RNG) methods are all signal processes in the optical domain, so they can efficiently overcome this rate limitation and have a great potential in generating ultrafast random numbers of several dozens or hundreds of Gb/s. However, there is no experimental report on its realization of AO-RNG. One of the obstacles in the way for the AO-RNG achievement is to implement the fast and real-time all-optical sampling of the entropy signals (i.e., laser chaos).#br#In this paper, we present a principal experimental demonstration of the feasibility in the all-optical sampling of the chaotic light signal through constructing a TOAD-based all-optical sampler with a polarization-independent semiconductor optical amplifier (SOA). Specifically, we experimentally generate chaotic laser signals using an optical feedback semiconductor laser and finally complete a 5 GSa/s real-time and high-fidelity all-optical sampling of the chaotic laser with a bandwidth of 6.4 GHz. Further experimental results show that whether the optical sampling period is proportional to the external cavity feedback time or not has a great effect on the weak periodic suppression of the chaotic signal: only when both of them are out of proportion, can the weak periodicity of the original chaotic signal be effectively eliminated; and this is favorable for the generation of high-quality physical random numbers. To the best of our knowledge, it is the first time to realize all-optical sampling of chaotic signal in experiments.
True random numbers occupy a core role in the field of encryption and security by virtue of their properties such as unpredictability and independence. In this paper, we propose a high-speed physical random number generator based on a dual-emission random fiber laser. The system improves the spectral bandwidth characteristics of the output signals by adjusting the pump power and the feedback length of the single mode fiber. This study effectively suppresses the autocorrelation feature by performing exclusive-OR operations on the forward and backward random laser signals, and obtain the random number sequence with a generation rate of 20 Gbps by post-processing with high-order finite difference and least significant bit extraction. In order to verify the practical application performance, we apply the random sequence as encryption key to digital image encryption, and the experimental results show that the generator has both theoretical security and practical application value.