Provably secure authenticated key exchange protocol under the CDH assumption

Constructing a secure key exchange protocol is one of the most challenging problems in information security. We propose a provably secure two-round two-party authenticated key exchange (2AKE) protocol based on the well-studied CDH assumption in eCK model to provide the strongest definition of security for key exchange protocol when using the matching session to define the partnership. The underlying hardness assumption (CDH assumption) of our protocol is weaker than these of four other provably secure 2AKE protocols in CK model or eCK model and the computational cost of our protocol is reasonable. We also present a three-round variant of our protocol to realize key conformation.     

On the independence assumption underlying subjective bayesian updating

Current rule-based, expert systems must cope with uncertain, subjective information. This is normally done by some form of probabilistic reasoning. Duda, Hart, and Nilsson have proposed one such scheme that is based on Bayes' rule. In this note we provide further mathematical analysis related to this rule. In particular, we prove the following proposition: if the assumptions made in deriving Duda et al.'s scheme are satisfied, together with the additional assumptions that the space of hypotheses is mutually exclusive and exhaustive, then no updating can take place. However, since this latter assumption is rarely satisfied in realistic systems, we then indicate how our analysis changes as exclusivity and exhaustivity are relaxed.     

Exploiting the generic viewpoint assumption

The generic viewpoint assumption states that an observer is not in a special position relative to the scene. It is commonly used to disqualify scene interpretations that assume special viewpoints, following a binary decision that the viewpoint was either generic or accidental. In this paper, we apply Bayesian statistics to quantify the probability of a view, and so derive a useful tool to estimate scene parameters.Generic variables can include viewpoint, object orientation, and lighting position. By considering the image as a (differentiable) function of these variables, we derive the probability that a set of scene parameters created a given image. This scene probability equation has three terms: the fidelity of the scene interpretation to the image data; the prior probability of the scene interpretation; and a new genericity term, which favors scenes likely to produce the observed image. The genericity term favors image interpretations for which the image is stable with respect to changes in the generic variables. It results from integration over the generic variables, using a low-noise approximation common in Bayesian statistics.This approach may increase the scope and accuracy of scene estimates. It applies to a range of vision problems. We show shape from shading examples, where we rank shapes or reflectance functions in cases where these are otherwise unknown. The rankings agree with the perceived values.     

On the finite controllability of conjunctive query answering in databases under open-world assumption

In this paper we study queries over relational databases with integrity constraints (ICs). The main problem we analyze is OWA query answering, i.e., query answering over a database with ICs under open-world assumption. The kinds of ICs that we consider are inclusion dependencies and functional dependencies, in particular key dependencies; the query languages we consider are conjunctive queries and unions of conjunctive queries. We present results about the decidability of OWA query answering under ICs. In particular, we study OWA query answering both over finite databases and over unrestricted databases, and identify the cases in which such a problem is finitely controllable, i.e., when OWA query answering over finite databases coincides with OWA query answering over unrestricted databases. Moreover, we are able to easily turn the above results into new results about implication of ICs and query containment under ICs, due to the deep relationship between OWA query answering and these two classical problems in database theory. In particular, we close two long-standing open problems in query containment, since we prove finite controllability of containment of conjunctive queries both under arbitrary inclusion dependencies and under key and foreign key dependencies. The results of our investigation are very relevant in many research areas which have recently dealt with databases under an incomplete information assumption: e.g., data integration, data exchange, view-based information access, ontology-based information systems, and peer data management systems.     

On an assumption guaranteeing boundary layer convergence of singularly perturbed systems

In a recent paper by B. A. Francis, an assumption was made that guaranteed convergence in the boundary layer for singularly perturbed linear systems, but the assumption was not discussed. This note examines this assumption in some detail. Verifiable sufficient and necessary conditions are given. Illustrative examples are presented.     

Relaxing the homogeneity assumption in usability testing

Much attention has been paid to the question of how many subjects are needed in usability research. Virzi (1992) modelled the accumulation of usability problems with increasing numbers of subjects and claimed that five subjects are sufficient to find most problems. The current paper argues that this answer is based on an important assumption, namely that all types of users have the same probability of encountering all usability problems. If this homogeneity assumption is violated, then more subjects are needed. A modified version of Virzi's model demonstrates that the number of subjects required increases with the number of heterogeneous groups. The model also shows that the more distinctive the groups, the more subjects will be required. This paper will argue that the simple answer 'five' cannot be applied in all circumstances. It most readily applies when the probability that a user will encounter a problem is both high and similar for all users. It also only applies to simple usability tests that seek to detect the presence, but not the statistical prevalence, of usability problems.     

Relaxing the homogeneity assumption in usability testing

Much attention has been paid to the question of how many subjects are needed in usability research. Virzi (1992) modelled the accumulation of usability problems with increasing numbers of subjects and claimed that five subjects are sufficient to find most problems. The current paper argues that this answer is based on an important assumption, namely that all types of users have the same probability of encountering all usability problems. If this homogeneity assumption is violated, then more subjects are needed. A modified version of Virzi's model demonstrates that the number of subjects required increases with the number of heterogeneous groups. The model also shows that the more distinctive the groups, the more subjects will be required. This paper will argue that the simple answer 'five' cannot be applied in all circumstances. It most readily applies when the probability that a user will encounter a problem is both high and similar for all users. It also only applies to simple usability tests that seek to detect the presence, but not the statistical prevalence, of usability problems.     

The indefinite closed world assumption

The inadequacy of the Closed World Assumption in dealing with indefinite information has led to the Generalised Closed World Assumption and the Extended Generalised Closed World Assumption. However, these approaches have serious shortcomings. In this paper, the Indefinite Closed World Assumption is proposed to overcome the shortcomings. It provides a desirable and simple logical interpretation of a database containing indefinite information.     

Progress assumption in concurrent systems

A denotational semantics and a sound and complete inequational proof systems for processes with varying degrees of liveness is presented. New insights onquiescence are given concerning the Jonsson characterisation of input/output system. A theory oftransational behaviour of the typecarry out until the end is developed as an application of this concept of process with liveness requirements. The proposed model fully reflects the parallel composition oftransactional requirements, giving the expected composite requirements.     

三强联合 推云端寄存服务

近日,信息通信技术服务提供商第一线安莱宣布携手系统和服务解决方案提供商戴尔和VMware,共同推出云端专属寄存服务(Cloud Dedicated Hosting,CDH)。该项服务利用虚拟化技术,帮助中小企业降低成本,提高生产力和数据可用性。该项服务已率先在香港市场推出,其后还会在台湾正式登陆。据市场研究机构IDC预测,到2014年,全球公     

Exact and approximate feedback linearization without the linear controllability assumption

The feedback linearization problem of nonlinear control systems has been solved in the literature under the assumption that the nonlinear system is linearly controllable. In this paper, the assumption of linear controllability is removed; necessary and sufficient conditions are given through Lie orbital symmetries, thus giving a geometric characterization of the problem in the analytic case. Both the exact and the approximate linearization problems are considered in the analytic case.     

The generic viewpoint assumption and planar bias

We show that generic viewpoint and lighting assumptions resolve standard visual ambiguities by biasing toward planar surfaces. Our model uses orthographic projection with a two-dimensional affine warp and Lambertian reflectance functions, including cast and attached shadows. We use uniform priors on nuisance variables such as viewpoint direction and the light source. Limitations of using uniform priors on nuisance variables are discussed.     

Efficient VSS free of computational assumption

VSS (verifiable secret sharing) is an important security mechanism in distributed computing. It is a secret sharing technique, where each distributed share holder can verify that he obtains a share of a unique secret. Two properties are important in VSS: efficiency and security, where the security of VSS includes two requirements, bindingness and hidingness. In any application of VSS, high efficiency is desired. In applications with critical security requirements, bindingness and hidingness are desired to be achieved without any computational assumption on hard mathematical problems. No existing VSS scheme is efficient enough in both computation and communication for cost-sensitive applications, especially in the popular ubiquitous and distributed computing environment. When security is required without any hard computational assumption, efficient VSS is even more difficult. To overcome this drawback in VSS, a new secret sharing protocol is proposed in this paper. It does not need any assumption or condition like hardness of computational problems to achieve bindingness and hidingness. Especially, its privacy is information-theoretic instead of statistical in most existing VSS schemes. It is very efficient in both computation and communication and costs much less than the existing VSS schemes. Therefore, it improves the efficiency of VSS and achieves the strongest security in VSS.     

Automated assumption generation for compositional verification

We describe a method for computing a minimum-state automaton to act as an intermediate assertion in assume-guarantee reasoning, using a sampling approach and a Boolean satisfiability solver. For a set of synthetic benchmarks intended to mimic common situations in hardware verification, this is shown to be significantly more effective than earlier approximate methods based on Angluin’s L* algorithm. For many of these benchmarks, this method also outperforms BDD-based model checking and interpolation-based model checking. We also demonstrate how domain knowledge can be incorporated into our algorithm to improve its performance.     

Randomized dining philosophers without fairness assumption

We consider Lehmann-Rabins randomized solution to the well-known problem of the dining philosophers. Up to now, such an analysis has always required a fairness assumption on the scheduling mechanism: if a philosopher is continuously hungry then he must eventually be scheduled. In contrast, we modify here the algorithm in order to get rid of the fairness assumption, and we claim that the spirit of the original algorithm is preserved. We prove that, for any (possibly unfair) scheduling, the modified algorithm converges: every computation reaches with probability 1 a configuration where some philosopher eats. Furthermore, we are now able to evaluate the expected time of convergence in terms of the number of transitions. We show that, for some malicious scheduling, this expected time is at least exponential in the number N of philosophers.Received: 14 June 2002, Accepted: 1 October 2003, Published online: 6 February 2004This paper is a revised and extended version of a communication given by the same authors, at 2nd IFIP Int. Conf. on Theoretical Computer Science (TCS@2002).     

Real-time indoor scene reconstruction with Manhattan assumption

This paper presents a novel end-to-end system for real-time indoor scene reconstruction, which outperforms traditional image feature point-based method and dense geometry correspondence-based method in handling indoor scenes with less texture and geometry features. In our method, we fully explore the Manhattan assumption, i.e. scenes are majorly consisted with planar surfaces with orthogonal normal directions. Given an input depth frame, we first extract dominant axes coordinates via principle component analysis which involves the orthogonal prior and reduce the influence of noise. Then we calculate the coordinates of dominant planes (such as walls, floor and ceiling) in the coordinates using mean shift. Finally, we compute the camera orientation and reconstruct the scene by proposing a fast scheme based on matching the dominant axes and planes to the previous frame. We have tested our approach on several datasets and demonstrated that it outperforms some well known existing methods in these experiments. The performance of our method is also able to meet the requirement of real-time with an unoptimized CPU implementation.

     

一种具有CDH问题安全性基于身份的签名方案

严格的安全证明需要较短的安全参数和较高的运行效率。为此,提出一种基于身份的签名方案IDSSTR,该方案具有可计算Diffie-Hellman问题的安全性规约,在线时自然有效,离线阶段也无需额外的条件,且验证过程也不变。为减小签名消息的总长度,给出具有消息恢复功能的IDSSTR修改版本。分析结果表明,可计算DiffieHellman问题的困难性与离散对数问题有着紧密联系,IDSSTR签名方案可为该困难问题提供安全保证。