Common randomness in information theory and cryptography. II. CRcapacity

For pt.I see ibid., vol.39, p.1121, 1993. The common randomness (CR) capacity of a two-terminal model is defined as the maximum rate of common randomness that the terminals can generate using resources specified by the given model. We determine CR capacity for several models, including those whose statistics depend on unknown parameters. The CR capacity is shown to be achievable robustly, by common randomness of nearly uniform distribution no matter what the unknown parameters are. Our CR capacity results are relevant for the problem of identification capacity, and also yield a new result on the regular (transmission) capacity of arbitrarily varying channels with feedback     

信息安全和密码技术分析

我国信息安全防护起步晚、基础差,而且网络安全防护能力也比较低,计算机的核心技术在美国,安全设备还要靠国外引进,缺乏安全保障,无法保障国家信息的安全。因此必须要对信息安全及密码技术有全面认识及应用。本文则对信息安全及密码技术探讨。     

Common randomness and secret key generation with a helper

We consider the generation of common randomness (CR), secret or not secret, by two user terminals with aid from a “helper” terminal. Each terminal observes a different component of a discrete memoryless multiple source. The helper aids the users by transmitting information to them over a noiseless public channel subject to a rate constraint. Furthermore, one of the users is allowed to transmit to the other user over a public channel under a similar rate constraint. We study the maximum rate of CR which can be thus generated, including under additional secrecy conditions when it must be concealed from a wiretapper. Lower bounds for the corresponding capacities are provided, and single-letter capacity formulas are obtained for several special cases of interest     

Sharing more information in gray visual cryptography scheme

Visual cryptography scheme (VCS) shares a binary secret image into several binary shadows, and the secret image can be visually revealed by stacking qualified shadows without computation. From the point of view of sharing secret information, VCS is not efficiency because of the large size expansion and low visual quality. In this paper, we introduce a general gray visual cryptography scheme, which can share more information, called Sharing More Information Gray Visual Cryptography Scheme (SMIGVCS). All the shadow pixels of VCS embed additional information to generate gray shadows of SMIGVCS, and the embedded information comes from the shadows of a polynomial-based secret sharing scheme (PSSS). In the revealing process, a vague secret image is visually decoded by stacking qualified shadows, and more information is revealed by computation. Compared with the two-in-one image secret sharing scheme (TiOISSS), our SMIGVCS can achieve smaller shadow size with acceptable visual quality.     

信息论的丰碑密码学的鼻祖--写在克劳德·E·香农博士去世两周年之际

两年前的2月24日,当新世纪的曙光刚刚照临人间两个多月时间,人们在分享着信息时代所带来的巨大便利迈向新的发展阶段的时刻,当代最伟大的数学家和贝尔实验室最杰出的科学家之一,现代信息论的创始人、密码学的鼻祖香农(Claude Elwood Shannon)博士却在同疾病顽强搏斗了五年之后,不幸永远地离开了他所挚爱的世界,享年84岁。香农为人类留下了极为宝贵的历史遗产,使人类长久地从中受益,从而赢得了人们的广泛尊重和纪念。 克劳德·E·香农1916年4月30日出生于美国密执安州的Petoskey。1936年香农毕业于密执安大学,获数学和电气工程学士学位,…     

Quantum information processing: cryptography, computation, andteleportation

Present information technology is based on the laws of classical physics. However, advances in quantum physics have stimulated interest in its potential impact on such technology. This article is an introductory review of three aspects of quantum information processing, cryptography, computation, and teleportation. The author serves up hors d'oeuvres on the relevant parts of quantum physics and the sorts of quantum systems which might form the building blocks for quantum processors. Quantum cryptography utilizes states of individual quantum systems for the transfer of conventional classical bits of information. The impossibility of measuring quantum systems without disturbing them guarantees the detection of eavesdropping and hence secure information transfer is possible. In a sense, teleportation is the inverse of cryptography, using more robust classical bits to faithfully transfer a quantum state through a noisy environment. Quantum computation utilizes the evolving quantum state of a complex system, which consists of many interacting individuals. If such a machine could be built, it would be capable of solving some problems which are intractable on any conventional computer; he illustrates this with Shor's (see Proc. 35th IEEE Symposium on Foundations of Computer Science, p.124, 1994) quantum factoring algorithm. Details are given of the current experimental achievements, proposals, and prospects for the future and of the patents granted to date     

An extension of the Shannon theory approach to cryptography

Shannon's information-theoretic approach to cryptography is reviewed and extended. It is shown that Shannon's random cipher model is conservative in that a randomly chosen cipher is essentially the worst possible. This is in contrast with error-correcting codes where a randomly chosen code is essentially the best possible. The concepts of matching a cipher to a language and of the trade-off between local and global uncertainty are also developed.     

ASP.NET中的加密技术--对称加密

加密术用于保护私有数据不被访问和修改，同时确保数据的完整性。在．NET之前，使用非托管的Win32 API加密解密数据是一件相当麻烦的事情。．NET Framework为数据加密提供了方便的机制。概述了ASP．NET中的数据加密，重点介绍了对称加密术的实现。使用的代码语言为C#。     

Quantum information theory

We survey the field of quantum information theory. In particular, we discuss the fundamentals of the field, source coding, quantum error-correcting codes, capacities of quantum channels, measures of entanglement and quantum cryptography     

The interactions between ergodic theory and information theory

Information theorists frequently use the ergodic theorem; likewise entropy concepts are often used in information theory. Recently, the two subjects have become partially intertwined as deeper results from each discipline find use in the other. A brief history of this interaction is presented in this paper, together with a more detailed look at three areas of connection, namely, recurrence theory, blowing-up bounds, and direct sample-path methods     

Logical basis for information theory and probability theory

A new logical basis for information theory as well as probability theory is proposed, based on computing complexity.     

Hypothesis testing and information theory

The testing of binary hypotheses is developed from an information-theoretic point of view, and the asymptotic performance of optimum hypothesis testers is developed in exact analogy to the asymptotic performance of optimum channel codes. The discrimination, introduced by Kullback, is developed in a role analogous to that of mutual information in channel coding theory. Based on the discrimination, an error-exponent functione(r)is defined. This function is found to describe the behavior of optimum hypothesis testers asymptotically with block length. Next, mutual information is introduced as a minimum of a set of discriminations. This approach has later coding significance. The channel reliability-rate functionE(R)is defined in terms of discrimination, and a number of its mathematical properties developed. Sphere-packing-like bounds are developed in a relatively straightforward and intuitive manner by relatinge(r)andE (R). This ties together the aforementioned developments and gives a lower bound in terms of a hypothesis testing model. The result is valid for discrete or continuous probability distributions. The discrimination function is also used to define a source code reliability-rate function. This function allows a simpler proof of the source coding theorem and also bounds the code performance as a function of block length, thereby providing the source coding analog ofE (R).     

Fundamental limits in information theory

Shannon information theory is in essence a study of "fundamental limits." In this paper we attempt to give the reader a taste of the nature of these limits and of how they relate to real situations in communication.     

Interference-free assignment grids. I. Basic theory

A mathematical method using linear algebra is developed for generating interference-free simplex channel assignment grids for base stations in the VHF land mobile band for large urban areas. The frequency assignment model checks for interference from adjacent channels, desensitization, transmitter intermodulation, and receiver intermodulation. The basic philosophy of the model is presented, and the required electromagnetic compatibility computations are reviewed. Both single-frequency and multiple-frequency (sharing) assignment strategies are described     

Team decision theory and information structures

This tutorial-survey paper introduces the problems of decentralized statistical decision making (team theory) where the decision makers have access to different information concerning the underlying uncertainties. Using a simple thematic example with variations, the paper introduces and explains various concepts and results of team theory as applied to economics, information theory, and decentralized control.     

New directions in cryptography

Two kinds of contemporary developments in cryptography are examined. Widening applications of teleprocessing have given rise to a need for new types of cryptographic systems, which minimize the need for secure key distribution channels and supply the equivalent of a written signature. This paper suggests ways to solve these currently open problems. It also discusses how the theories of communication and computation are beginning to provide the tools to solve cryptographic problems of long standing.     

On compound state and mutual information in quantum information theory (Corresp.)

A quantum mechanical compound state of an input state and its output state generated through a communication channel is constructed. The mutual information of quantum communication theory is defined by using the compound state, and its fundamental properties are studied.