A new dual entropy core true random number generator

The entropy produced by a conventional single chaotic map based true random number generator (TRNG) is usually limited due to the finite number of Lyapunov exponents. In this work, we present a new dual entropy core TRNG architecture which is capable of producing high levels of randomness using hardware redundancy. Mathematical models of conventional and proposed TRNG architectures have been developed for a comparative analysis of the statistical and randomness properties. Our theoretical studies showed that the proposed architecture which employs Bernoulli map as the entropy source, has an inherently symmetric probability density function with zero mean. Using a practical information metric, T-entropy, we demonstrated that the proposed architecture performs better in terms of randomness, for a wide range of control parameter values when compared to its single entropy core counterpart. A proof of concept prototype of the proposed architecture is designed and implemented using a field programmable analog array integrated circuit. Random numbers acquired from the prototype have successfully passed all NIST 800.22 statistical tests.     

A unity bit coding method by negative feedback

Signal-to-noise performances of a unity bit coding method and the characteristics of an experimental video encoder based upon the principle are described. The system contains a signal integration process in addition to the original delta modulator and features capability of transmitting dc component of input signal. The characteristics of the quantizing noise to the signal frequency, the signal amplitude and the integrator time constant are obtained theoretically as well as experimentally. The characteristics of periodical noise which are inherent to the proposed system are also investigated. The design and the characteristics of an experimental encoder for digital transmission of video signals are described as examples of the experimental equipment constructed to demonstrate the realizability of the principle. The experimental results show that considerably good reproduction of video pictures is obtained with sampling frequency as low as 30 Mc and suggest that the proposed system well fulfills the purpose.     

Coexistence of chaos-based and conventional digital communication systems of equal bit rate

Chaos-based communication systems represent a new category of spread-spectrum communication systems, whose working principle differs significantly from conventional direct-sequence and frequency-hopping spread-spectrum systems. However, like all other kinds of spread-spectrum systems, chaos-based systems are required to provide reasonable bit error performance in the presence of a narrow-band signal which can be generated from an intruder or a coexisting conventional communication system. In particular, the frequency band of this foreign narrow-band signal can fall within the bandwidth of the chaos-based system in question. Such a scenario may occur in normal practice when chaos-based systems are introduced while the conventional systems are still in operation. It is therefore important to examine the coexistence of chaos-based and conventional systems. The objective of this paper is to evaluate the performance of the chaos-based system when its bandwidth overlaps with that of a coexisting conventional system. In particular, the chaos-based systems under study are the coherent chaos shift keying (CSK) system and the noncoherent differential CSK (DCSK) system, whereas the conventional system used in the study employs the standard binary phase shift keying scheme. Also, both the chaos-based and conventional systems are assumed to have identical data rates. Analytical expressions for the bit-error rates are derived, permitting evaluation of performance for different noise levels, power ratios and spreading factors. Finally, results from computer simulations verify the analytical findings.     

A wideband quadrature generator IC using a varactor-compensated feedback network

In this paper a novel quadrature generator is presented that exhibits a 110% operating frequency bandwidth. Existing circuits are unable to provide a quadrature signal over such a large fractional bandwidth. They are also highly susceptible to component tolerances that can often shift the center operating frequency rendering the circuit unusable. In this work, this issue is mitigated with the use of a negative feedback network that is able to actively compensate the circuit using varactors to match the operating frequency. In this manner, the bandwidth of the quadrature generator can be significantly increased. Simulation results show an operating frequency span from 1 to 6 GHz while maintaining a phase error below 5° and ±2 dB in amplitude error. The circuit, without bonding pads, uses an area of only 0.17 mm².     

A universal statistical test for random bit generators

A new statistical test for random bit generators is presented which, in contrast to presently used statistical tests, is universal in the sense that it can detect any significant deviation of a device's output statistics from the statistics of a truly random bit source when the device can be modeled as an ergodic stationary source with finite memory but arbitrary (unknown) state transition probabilities. The test parameter is closely related to the device's per-bit entropy which is shown to be the correct quality measure for a secret-key source in a cryptographic application. The test hence measures the cryptographic badness of a device's possible defect. The test is easy to implement and very fast and thus well suited for practical applications. A sample program listing is provided.This work was supported by Omnisec AG, Switzerland. A preliminary version of this paper was presented at Crypto '90, Aug. 11–15, 1990, Santa Barbara, CA.     

A frequency aliasing approach to chaos-based cryptosystems

In this paper, a chaos-based cryptosystem using sampled chaos signals with frequency-domain aliasing is proposed. In this scheme, a higher degree of randomness of the running-key sequence is obtained, and an additional random seed consisting of the sampling frequency as the parameter is introduced. This leads to an enhancement of the cryptosystem security. Numerical and simulation results of a Lorenz cryptosystem are given to demonstrate the performance and effectiveness of the proposed approach.     

A bit is a bit is a bit?

Bits are among the most anonymous, most elusive entities in the universe. Bits weigh nothing, occupy no space, obey no physical law, can be created spontaneously from nothingness, and can be endlessly replicated. Each in itself is the merest quantum of the Information Age, yet taken together all those little 1s and 0s are acting as if they were the most important force on the planet. And if you want indestructibility, then a bit is forever. The author briefly discusses the role of the bit in today's society     

True random bit generation from a double-scroll attractor

In this paper, a novel true random bit generator (TRBG) based on a double-scroll attractor is proposed. The double-scroll attractor is obtained from a simple model which is qualitatively similar to Chua's circuit. In order to face the challenge of using the proposed TRBG in cryptography, the proposed TRBG is subjected to statistical tests which are the well-known Federal Information Processing Standards-140-1 and Diehard test suite in the area of cryptography. The proposed TRBG successfully passes all these tests and can be implemented in integrated circuits.     

A conditional entropy bound for a pair of discrete random variables

LetX, Ybe a pair of discrete random variables with a given joint probability distribution. For0 leq x leq H(X), the entropy ofX, define the functionF(x)as the infimum ofH(Ymid W), the conditional entropy ofYgivenW, with respect to all discrete random variablesWsuch that a)H(Xmid W) = x, and b)WandYare conditionally independent givenX. This paper concerns the functionF, its properties, its calculation, and its applications to several problems in information theory.     

A uniformly distributed analog random voltage generator

Whereas random number generating methods are numerous, uniformly distributed analog random voltages are difficult to obtain directly. A method based upon the use of a point process is proposed, which leads to a practical noise generator with accurate uniform amplitude distribution, which is very easy to implement.     

A random sequence generator based on chaotic circuits

In this paper, a random sequence generator based on chaotic circuits is presented. Fundamental principle and experimental circuit have been carried out in case of Chua's circuit. The statistical results are in good agreement with probability characteristics of random sequence.     

软件随机数发生器设计的安全问题

随机数在应用程序中被广泛使用，很多的程序设计往往使用简单的线性适配随机发生器(函数)；由于它的可预测性，存在安全方面的隐患。因此，一个健壮的随机数发生器有着不可忽略的重要性．对Windows下健壮的随机数发生器的设计做了论述，并给出必要的实现代码。     

A synthesized method to improve coherence in semiconductor lasersby electrical feedback

A method for improving coherence in semiconductor lasers by negative electrical feedback is proposed for stabilization of the center frequency of the field spectrum, linewidth reduction of the field spectrum, frequency tracking to another highly coherent laser, and stable and wideband frequency sweep. Experimental center frequency stabilization of the master laser showed that the magnitude of frequency fluctuations was reduced to 50 kHz at the integration time τ=3 s. The linewidth of the master laser was reduced to 100 kHz, which was 1/50 that of the free running laser. Under these frequency control conditions, the frequency of the slave laser was controlled so that the phase of the heterodyne signal between the master and the slave lasers could be locked to that of a stable microwave synthesizer. The slave laser frequency tracked accurately to the master laser frequency     

Development of a new composite pseudo random number generator

We develop a new composite pseudo random number generator called the Composite Sherif-Dear (CSD) generator. The proposed generator satisfies stringent theoretical criteria for the quality of the sequence it produces; and is easy to understand and implement in a portable way.     

A new control strategy to improve the performance of a PWM AC to DCconverter under unbalanced operating conditions

Abnormal harmonics of significant magnitude are generated at the output and input terminals of a PWM (pulse-width-modulated) AC-to-DC power converter under unbalanced operating conditions. A new control strategy is presented to selectively cancel the generated lower-order abnormal harmonics at the output and input terminals and thereby to preserve the high-performance features of a PWM AC-to-DC power converter. The proposed technique essentially involves computing the sequence components of the unbalanced input supply and suitably counter-unbalances the PWM gating signals of the power converter switches to cancel the generated abnormal harmonics. The technique is essentially a feedforward approach and is suitable for higher-power GTO (gate turn-off thyristor) type PWM AC-to-DC power converters. A procedure for implementing this technique in real time is discussed. Selected results are verified experimentally on a prototype PWM AC-to-DC power converter     

Combining speech coders and entropy coders to reduce the bit rate in the compression of speech

The combination of speech coders and entropy coders is investigated, for bit rate reduction. Three speech coders of the celp (code excited linear prediction) type are considered and the residual correlation in lsp (line spectrum pairs) coefficients and gains in a speech frame is exploited. The lossless entropy coders use Huffman, Lzw (lempel ziv welch) and gzip (LZ-Huffrnan) techniques. The greatest efficiency is provided by the adaptive Huffman approach, with a 15 % gain in each type of compressed parameter and an overall average bit rate reduction of 7 % for the FS1016 coder and 5 % for the Tetra and lbc coders.     

Community based feedback techniques to improve video search

In this paper, we present a novel approach to aid users in the difficult task of video search. We use a graph based model based on implicit feedback mined from the interactions of previous users of our video search system to provide recommendations to aid users in their search tasks. This approach means that users are not burdened with providing explicit feedback, while still getting the benefits of recommendations. The goal of this approach is to improve the quality of the results that users find, and in doing so also help users to explore a large and difficult information space. In particular we wish to make the challenging task of video search much easier for users. The results of our evaluation indicate that we achieved our goals, the performance of the users in retrieving relevant videos improved, and users were able to explore the collection to a greater extent.     

Adaptive downsampling to improve image compression at low bit rates.

At low bit rates, better coding quality can be achieved by downsampling the image prior to compression and estimating the missing portion after decompression. This paper presents a new algorithm in such a paradigm, based on the adaptive decision of appropriate downsampling directions/ratios and quantization steps, in order to achieve higher coding quality with low bit rates with the consideration of local visual significance. The full-resolution image can be restored from the DCT coefficients of the downsampled pixels so that the spatial interpolation required otherwise is avoided. The proposed algorithm significantly raises the critical bit rate to approximately 1.2 bpp, from 0.15-0.41 bpp in the existing downsample-prior-to-JPEG schemes and, therefore, outperforms the standard JPEG method in a much wider bit-rate scope. The experiments have demonstrated better PSNR improvement over the existing techniques before the critical bit rate. In addition, the adaptive mode decision not only makes the critical bit rate less image-independent, but also automates the switching coders in variable bit-rate applications, since the algorithm turns to the standard JPEG method whenever it is necessary at higher bit rates.     

一种基于FPGA的真随机数发生器设计与实现

设计并实现了一种基于FPGA的真随机数发生器,利用一对振荡环路之间的相位漂移和抖动以及亚稳态作为随机源,使用线性反馈移位寄存器的输出与原始序列运算作为后续处理。在Xilinx Virtex-5平台的测试实验中,探讨了振荡器数量以及采样频率等参数对随机序列的统计特性的影响。测试结果表明本设计产生的随机序列能够通过DIEHARD测试,性能满足要求。由于仅使用了普通逻辑单元,使得本设计能够迅速移植到ASIC设计,大大缩短了开发周期。