Expanded quantum cryptographic entangling probe

A generalized quantum circuit and design are given for an optimal entangling probe to be used in attacking the BB84 protocol of quantum key distribution and yielding maximum information to the probe. Probe photon polarization states become optimally entangled with the BB84 signal states on their way between the legitimate transmitter and receiver. The present design generalizes an earlier one by Brandt [J. Mod. Optics 52 2177 (2005)] to include a complete range of error rates that can be induced by the probe.     

Editorial - Group-oriented cryptographic protocols

Group-oriented cryptographic protocols are foundational for the security of various group applications, such as digital conferencing, groupware, group communication systems, computer-supported collaborative work-flow systems, multiuser information distribution and sharing, data base and server replication systems, peer-to-peer and ad-hoc groups, group-based admission and access management, electronic voting and election, applications in federative or distributed environment, etc.     

Data security: a cryptographic approach

This paper is a review of the subject of data security. The probabilistic as well as the computational complexity approaches to this subject have been discussed. Ciphers examined in some depth include block random ciphers, stream ciphers, the DES cipher adopted by the National Bureau of Standards, USA, the RSA computational complexity cipher, the Merkle and the Hellman trap-doorKnapsack cipher.     

Defense frontier analysis of quantum cryptographic systems

When a quantum cryptographic system operates in the presence of background noise, security of the key can be recovered by a procedure called key distillation. A key-distillation scheme effective against so-called individual (bitwise-independent) eavesdropping attacks involves sacrifice of some of the data through privacy amplification. We derive the amount of data sacrifice sufficient to defend against individual eavesdropping attacks in both BB84 and B92 protocols and show in what sense the communication becomes secure as a result. We also compare the secrecy capacity of various quantum cryptosystems, taking into account data sacrifice during key distillation, and conclude that the BB84 protocol may offer better performance characteristics than the B92.     

Alternative design for quantum cryptographic entangling probe

An alternative design is given for an optimized quantum cryptographic entangling probe for attacking the BB84 protocol of quantum key distribution. The initial state of the probe has a simpler analytical dependence on the set error rate to be induced by the probe than in the earlier design. The new device yields the same maximum information to the probe for a full range of induced error rates. As in the earlier design, the probe contains a single CNOT gate which produces the optimum entanglement between the BB84 signal states and the correlated probe states.     

High-numerical-aperture scalar imaging

The equation for partially coherent high-numerical-aperture scalar imaging was originally derived by Cole et al. [Jpn. J. Appl. Phys. 31, 4110 (1992)]. Here I present an alternative derivation, based on the plane-wave spectral representation of propagation, which can, at least in some respects, be viewed as more straightforward.     

Extensions of access structures and their cryptographic applications

In secret sharing schemes a secret is distributed among a set of users ${\mathcal{P}}In secret sharing schemes a secret is distributed among a set of users P{\mathcal{P}} in such a way that only some sets, the authorized sets, can recover it. The family Γ of authorized sets is called the access structure. To design new cryptographic protocols, we introduce in this work the concept of extension of an access structure: given a monotone family G ì 2^P{{\it \Gamma} \subset 2^\mathcal{P}} and a larger set P^￠ = P è[(P)\tilde]{\mathcal{P}^{\prime} = \mathcal{P} \cup \tilde{\mathcal{P}}}, a monotone access structure G^￠ ì 2^P￠{{\it \Gamma}^{\prime}\subset 2^{\mathcal{P}^{\prime}}} is an extension of Γ if the following two conditions are satisfied: (1) The set P{\mathcal{P}} is a minimal subset of Γ′, i.e. P ? G^￠{\mathcal{P} \in {\it \Gamma}^{\prime}} and P - {R_i} ? G^￠{\mathcal{P} - \{R_i\}\notin {\it \Gamma}^{\prime}} for every R_i ? P{R_i \in \mathcal{P}}, (2) A subset A ì P{A \subset \mathcal{P}} is in Γ if and only if the subset A è[(P)\tilde]{A \cup \tilde{\mathcal{P}}} is in Γ′. As our first contribution, we give an explicit construction of an extension Γ′ of a vector space access structure Γ, and we prove that Γ′ is also a vector space access structure. Although the definition may seem a bit artificial at first, it is well motivated from a cryptographic point of view. Indeed, our second contribution is to show that the concept of extension of an access structure can be used to design encryption schemes with access structures that are chosen ad-hoc at the time of encryption. Specifically, we design and analyze a dynamic distributed encryption scheme and a ciphertext-policy attribute-based encryption scheme. In some cases, the new schemes enjoy better properties than existing ones.     

Simulations of continuum coherent states and its use in quantum cryptographic systems

Abstract

The continuum states formalism is suitable for field quantization in optical fibre; however, they are harder to use than discrete states. On the other hand, a Hermitian phase operator can be defined only in a finite dimensional space. We approximated a coherent continuum state by a finite tensor product of coherent states, each one defined in a finite dimensional space. Using this, in the correct limit, we were able to obtain some statistical properties of the photon number and phase of the continuum coherent states from the probability density functions of the individual, finite dimensional, coherent states. Then, we performed a simulation of the BB84 protocol, using the continuum coherent states, in a fibre interferometer commonly used in quantum cryptography. We observed the fluctuations of the mean photon number in the pulses that arrive at Bob, which occurs in the practical system, introduced by the statistical property of the simulation.     

一种自适应容忍入侵的密码协议安全运行防护系统

针对密码协议在实际运行中遭受攻击的问题,设计了自适应容忍入侵的密码协议安全运行防护系统.该防护系统主要由入侵检测模块和容忍入侵模块组成.入侵检测模块采用基于特征和异常的混合入侵检测模式,使用有限状态自动机(FSM)匹配密码协议执行中的各状态参数,实时检测密码协议的运行情况,并把检测结果发送给容忍入侵模块,触发容忍入侵模块根据预先设计好的自适应调整策略,对密码协议的运行进行调节,以达到容忍攻击的目的.采用模拟试验对系统模型进行了仿真测试,测试结果表明该模型能够在一定程度上成功检测对密码协议的攻击行为,并具有容忍某些特定类型攻击的能力.     

Homogeneous and evanescent contributions in scalar near-field diffraction

The contributions of homogeneous and evanescent waves to two-dimensional near-field diffraction patterns of scalar optical fields are examined in detail. The total plane-integrated intensities of the two contributions are introduced as convenient measures of their relative importance. As an example, the diffraction of a plane wave by a slit is considered.     

On weak differential uniformity of vectorial Boolean functions as a cryptographic criterion

We study the relation among some security parameters for vectorial Boolean functions which prevent attacks on the related block cipher. We focus our study on a recently-introduced security criterion, called weak differential uniformity, which prevents the existence of an undetectable trapdoor based on imprimitive group action. We present some properties of functions with low weak differential uniformity, especially for the case of power functions and 4-bit S-Boxes.     

Reconstruction of scalar time-delay system models

A new method is proposed for the reconstruction of scalar time-delay system models. The method is simple, fast, and applicable to the analysis of noisy data. The performance of the proposed method is illustrated by application to the time series obtained in a numerical experiment (with a possible noise component) and in a real radiophysical system.     

Structural analogies for scalar field problems

This paper describes how general-purpose finite element structural analysis computer programs can be used, without modification, to solve various scalar field equations such as the wave equation, the Helmholtz equation, Laplace's equation, Poisson's equation, the heat equation and the telegraph equation, as well as mixed field problems (such as coupled structural-acoustic problems) which involve these equations.     

Henkel plots in a thermally demagnetized scalar Preisach model

The implications of thermal demagnetization with respect to the observation of interaction effects in Henkel plots are discussed within the framework of a scalar moving Preisach model. The Preisach distribution is assumed to be a product of a Gaussian coercive field distribution and a Gaussian interaction field distribution. Numerical calculations of the magnetizing and demagnetizing remanences show that, by contrast with other demagnetizing procedures, thermal demagnetization yields Henkel plots whose direction of curvature is uniquely related to the sign of the mean interaction field. In particular, a distribution of interaction fields which is symmetric about the origin yields the same linear Wohlfarth relation as a completely noninteracting system, while demagnetizing (magnetizing)-like mean fields always curve the Henkel plot below (above) the Wohlfarth line. The simple linearity of the Henkel plot in the absence of mean field effects was exploited to evaluate the effectiveness of a recent proposal for experimentally suppressing shape demagnetizing effects in perpendicular recording media     

Nonlinear signal-processing model for scalar diffraction in optical recording

A nonlinear signal-processing model is derived for the optical recording channel based on scalar diffraction theory. In this model, the signal waveform is written in closed form as an explicit function of the channel bits that are stored on an optical disk, thereby comprising both linear and nonlinear terms. Its explicit dependence on the channel bits makes this model well suited for signal-processing purposes. With the model it is also convenient to assess the importance of nonlinear contributions to the signal waveform. The model is applied for one-dimensional optical storage as well as for two-dimensional (2D) optical storage in which bits are arranged on a 2D hexagonal lattice. Signal folding is addressed as a typical nonlinear issue in 2D optical storage and can be eliminated by recording of pit marks of sizes considerably smaller than the size of the hexagonal bit cell. Further simplifications of the model with only a limited number of channel parameters are also derived.     

Alternative to the karatsuba algorithm for software implementations of GF(2n) multiplications

A new approach to subquadratic space complexity GF(2ⁿ) multipliers has been proposed recently. The corresponding algorithm for software implementations is developed. While its recursive implementation is as simple as that of the Karatsuba algorithm, it requires much less memory to store the look-up table. Therefore it is quite suitable for memory-constrained applications, for example smart cards.     

Nonparaxial scalar treatment of sinusoidal phase gratings

Scalar diffraction theory is frequently considered inadequate for predicting diffraction efficiencies for grating applications where lambda/d>0.1. It has also been stated that scalar theory imposes energy upon the evanescent diffracted orders. These notions, as well as several other common misconceptions, are driven more by an unnecessary paraxial approximation in the traditional Fourier treatment of scalar diffraction theory than by the scalar limitation. By scaling the spatial variables by the wavelength, we have previously shown that diffracted radiance is shift invariant in direction cosine space. Thus simple Fourier techniques can now be used to predict a variety of wide-angle (nonparaxial) diffraction grating effects. These include (1) the redistribution of energy from the evanescent orders to the propagating ones, (2) the angular broadening (and apparent shifting) of wide-angle diffracted orders, and (3) nonparaxial diffraction efficiencies predicted with an accuracy usually thought to require rigorous electromagnetic theory.     

Monochromatic scalar fields with maximum focal irradiance

The monochromatic scalar fields that achieve the maximum focal irradiance for a given input power and directional spread are found through a variational approach. In two dimensions, the maximum focal irradiance is found to be proportional to the sine of the directional spread as well as the input power. In three dimensions, the corresponding relation is found in parametric form.