Identity-based mix: Anonymous communications without public key certificates

A mix is a cryptographic construction for anonymizing communications. Existing mixes require that the public key certificates of mix servers have been distributed among users. In this paper, we propose a new mix that uses techniques from identity-based cryptography. Our mix does not require any public certificates; as long as the users know the identities of mix servers, the mix can anonymize messages. We give proofs of correctness and privacy, as well as analysis of efficiency.     

A tutorial on public key cryptography

Public key cryptography provides the means for establishing instantaneous, secure communication between any two persons or any two computers. The prior exchange of a secret quantity, called the cryptographic key, is not necessary. In this paper, the underlying mathematical principles of public key (PK) cryptography are informally introduced and two realizations of the concept are described.     

A practical look at ATPG

Book Reviewed: Digital Logic Testing and Simulation, 2nd edition, by Alexander Miczo (Wiley-Interscience, 2003, ISBN 0-471-43995-9, 696 pp., $115).     

A double look at duality

The two forms of duality that are encountered most frequently by the systems theorist-linear duality and convex duality-are examined. Linear duality has a strong algebraic characterization which extends to other structures such as groups and modules. Convex duality, on the other hand, capitalizes so strongly on the vector space structure that the resulting powerful theory (which is typically interpreted geometrically) loses the algebraic flavor of its roots. An algebraic characterization of convex duality is presented that generalizes the standard algebraic characterization of linear duality. This provides a link between the two forms of duality most important for the systems theorist. The algebraic and geometric interpretations together give a double view of duality as used in systems theory     

A closer look at termination

Summary Several methods for proving that computer programs terminate are presented and illustrated. The methods considered involve (a) using the no-infinitely-descending-chain property of well-founded sets (Floyd's approach), (b) bounding a counter associated with each loop (loop approach), (c) showing that some exit of each loop must be taken (exit approach), or (d) inducting on the structure of the data domain (Burstall's approach). We indicate the relative merit of each method for proving termination or non-termination as an integral part of an automatic verification system.     

A geometric look at corner cutting

In this paper we consider conrner cutting and convexity preserving interpolatory refinement schemes in the plane and on the sphere. Using well-known facts from projective geometry we present a unified approach to such schemes and geometric derivations of simple conditions which guarantee that a scheme generates C¹-curves. Our results generalize all of the results known so far and provide the ground for a new convexity preserving C¹-interpolation scheme with a simple direct shape handle.     

A big-picture look at enterprise architectures

It makes sense to plan the growth of your information systems. But many attempts to create a road map start at the wrong level. Ensuring a consistent, coherent vision to direct the evolution of the enterprise's information systems is difficult enough with a development framework. Without one, it's impossible. The concepts we outline are just a task list in the work to establish an enterprise architecture, but they give you some idea of the breadth of the job ahead of you. However, we hope we've given you a start toward a more realistic vision of your enterprise architecture     

A minimalistic look at widening operators

We consider the problem of formalizing in higher-order logic the familiar notion of widening from abstract interpretation. It turns out that many axioms of widening (e.g. widening sequences are ascending) are not useful for proving correctness. After keeping only useful axioms, we give an equivalent characterization of widening as a lazily constructed well-founded tree. In type systems supporting dependent products and sums, this tree can be made to reflect the condition of correct termination of the widening sequence.     

A critical look at open source

In recent years, open source software - more properly, free and open source software - has emerged as one popular solution to the so-called "software crisis". Advocates regard F/OSS as an agile, practice-led initiative that addresses three key issues namely cost, time scale and quality. F/OSS products are usually freely available for public download. The collaborative, parallel efforts of globally distributed developers allow many F/OSS products to be developed much more quickly than conventional software. Many F/OSS offerings are recognized for their high standards of reliability, efficiency, and robustness; products such as GNU/Linux, Apache, and Bind have become "category killers" stifling the incentive to develop any competing products.     

Design of animated pedagogical agents—A look at their look

A well-established effect of animated agents in educational and other contexts is their potential to motivate and engage. “Increased motivation in users” is also one of the more frequent answers given to the question, “What is gained by adding an animated pedagogical agent to an intelligent tutoring system?”To further develop and exploit this potential, there are, however, several issues that need to be resolved. In this article we discuss the visual form and look of animated pedagogical agents. A survey is presented of how the area is approached (and, in particular, not approached) in research on animated pedagogical agents. Two possible reasons are proposed as to why visual form and look are so little addressed are also proposed. We also propose and discuss some key aspects of look that merit a systematic approach in future research.The main thesis of the paper is that users’ visuo-aesthetic experience of animated pedagogical agents is too important with respect to the goals to motivate and engage, to be treated as a secondary issue. We do not deny that there are other pressing and fundamental issues that need to be solved, such as those concerning the content of the support and the competence level of agents, as well as various design elements that can contribute to making animated agents lifelike. But we argue that visual rendering issues are pressing and need to be seriously addressed as well.     

Simplifying public key management

Many security protocols in use today were designed under the assumption that some form of global distributed public key infrastructure would eventually emerge to address key management problems. These protocols go back to the early 1990s, when a universal PKI was thought to be just around the corner. Ten years later, it's still just around the corner, and it probably always will be. Consequently, existing protocols originally designed to rely on a global PKI must either employ ad hoc solutions or use any public key that turns up, because the only alternative is not to use any keys at all. In the absence of a PKI, system administrators can incorporate alternative approaches that are easy to use, transparent to end users, and have a low unit cost.     

多模式多变量公钥密码体制

针对量子计算机对公钥密码体制的挑战,提出一种能抵抗量子算法的多模式多变量公钥密码算法。量子计算机在解决多变量多项式问题并无高效算法,在传统多变量公钥密码体制的基础上,使用多分支模式,在分支内部采用加模式、减模式和迭代模式,增强了多变量公钥密码体制的安全性。通过分析各种常见攻击的复杂度,多模式多变量公钥密码体制能有效抵抗各种攻击,可以应用于加解密、签名和数据完整性验证。