基于RSA的广播加密新方案

根据RSA加密系统和小公钥的动态放大技术,提出了一种面向不同组的用户的广播加密新方案。在新方案中,每个用户都采用相同的小公钥,利用它可同时对不同组的接收者进行广播加密传送消息。加密阶段发送者根据接收用户数计算安全的放大因子,然后引入随机整数,将明文消息加密生成广播传送的密文。这样不仅提高了RSA的加密速度,而且可同时抵御低指数攻击和重发攻击,并实现对不同组的接收者进行广播加密传送消息。     

应用于数据库安全保护的加解密引擎系统

针对系统业务数据安全存储问题,采用加解密引擎服务对应用端发送数据进行加密,根据用户ID来识别不同用户的传输命令,利用用户私有的KEY进行加密存储。该方案在云计算平台下具有保护用户数据存储安全、隔离数据的功能。当应用端用户查询已加密数据时,加解密引擎服务端根据用户ID读取缓存区用户密钥,解密数据返回给应用端明文数据。当加解密系统和第三方应用进行集成时,加解密引擎将载人用户定义的加密算法、加密矢量等信息,按照用户自身的密钥加密敏感数据,可保证用户敏感数据存储安全并隔离不同用户的业务数据。以某市人口库系统集成为例,验证了方案的可行性。     

可搜索加密研究进展综述

随着云计算的迅速发展,为保护用户外包数据的安全和用户隐私,越来越多的企业和用户选择将数据加密后上传。因此,对云服务器上加密数据的有效搜索成为用户关注的重点。可搜索加密技术是允许用户对密文数据进行检索的密码原语,利用云服务器的强大计算资源进行关键词检索。根据使用密码体制的不同,介绍了可搜索加密的分类,将其分为对称可搜索加密和非对称可搜索加密。基于这种分类,首先介绍了典型方案,之后从可搜索加密的语句表达能力和安全性2方面进行介绍,并指出了该领域当前研究中急需解决的问题及未来研究方向。     

可信数据库环境下面向服务的自适应密文数据查询方法

实现加密数据的高效安全查询是保证可信数据库安全性和实用性的关键.与目前加密数据查询采用的静态密文分段方法不同,论文基于加密数据的分布和用户查询类型、分布规律,提出了一种自适应加密索引AEI(Adaptive Encrypted Index),实现面向服务的加密数据查询.AEI通过分析查询服务对查询性能的影响,根据承载服务特性、密文数据分布、用户查询分布采用自适应的加密索引划分策略,获得更好的加密数据查询性能.基于AEI方法可在可信数据库环境下实现密文数据查询,并通过了相关性能测试.实验数据表明,与其它加密数据查询方法相比,AEI方法具有更好的适应性和更高的加密数据查询效率.     

支持关键字更新的基于属性可搜索加密方案

针对云存储环境中重要通知、广播消息、数据共享等敏感性较高的数据访问控制需求,提出和设计出一种适用于云存储环境支持关键字更新的可搜索加密方案。方案中的文件明文采用基于属性的加密算法,可以实现文件密文只加密一次就可被多个用户私钥搜索,避免了针对不同用户数据拥有者需要多次加密的问题,降低了网络开销。但是现有的基于属性的可搜索加密方案无法实现文件索引的更新,针对此问题,采用带计数器的布隆过滤器对文件关键字进行处理,能够允许用户在索引密文中添加或者删除关键字,实现文件索引的动态更新,提高了检索效率。给出方案的正确性分析、安全分析以及效率分析。分析结果表明:文件索引和陷门经过带计数器的布隆过滤器并进行向量加密后,的确能够实现增加和删除关键字;采用对称加密的思想对文件和索引进行加密后,明文和索引也都是安全的;通过与其他方案的计算量和适应性对比,可以发现方案的计算量较低,适应性强。     

公钥可搜索加密体制综述

伴随着云计算技术的广泛应用,外包到云服务器存储的数据通常采用密文方式进行存储以确保数据安全和用户隐私。可搜索加密体制允许用户对密文数据通过关键词进行检索,从而极大减少了数据共享用户的通信和计算开销。基于公钥的可搜索加密体制解决了对称可搜索加密体制中的密钥分发问题而受到广泛关注。本文侧重于阐述公钥可搜索加密体制的研究进展,描述了它的形式化定义、安全模型;分析和讨论了典型的公钥可搜索加密体制的设计机理、相关的扩展方案以及它们的安全性问题。最后,本文还讨论了公钥可搜索加密体制的应用场景,并指出了未来可能的发展方向。     

复杂语义可搜索加密研究

可搜索加密是一种支持用户在密文上进行关键词检索的密码学原语,能够为用户节省大量的网络和计算开销.进一步地,复杂语义可搜索加密,主要包括通配符可搜索加密、模糊关键词可搜索加密和多关键词可搜索加密,能够支持用户对密文进行各种形式多样化的搜索,而不局限于完整的单关键词搜索,更切合用户的实际搜索情形.本文主要从上述三类复杂语义...     

一种安全有效的小公钥RSA加密协议及其应用

提出了一种采用小公钥的RSA加密协议．该协议允许多个用户都采用相同的小公钥，在对这些用户发送加密信息时，发方可根据要发送的用户数对小公钥进行动态放大，而每个接收者在解密时可根据私钥动态计算解密密钥．这样既提高了RSA的加密速度，同时可抵御对RSA的低指数加密攻击．     

字符型密码随机加密与解密算法的设计与实现

为防止网络应用系统中字符型密码被非法用户通过“跑字典”破译,并能为网络用户找回丢失的密码,同时也为远程访问数据库做数据同步提供便利,提出一种对字符型密码采用线性随机加密与解密的算法.该算法中的加密参数随机生成,并在密文结构中采用了随机混淆手段,对同一明文可产生不同的密文,且算法可逆.通过JavaScript语言实现了该算法,验证了该算法的可行性和有效性.     

Web服务身份验证与数据加密传输协议的设计与实现

文章讨论了Web服务用户身份验证和数据库数据加密传输的方法,提出了采用非对称加密算法来传送对称加密密钥,采用SOAP头来传递验证信息和经过加密的对称密钥的认证协议,并用C#实现了这一网上银行的Web服务身份验证及SQL2000数据库数据加密传输协议,实际测试表明这种基于Web服务的用户身份验证是安全有效的,可用于网上银行.     

A Location Management Scheme Supporting Route Optimization for Mobile Hosts

Using the Internet as a foundation for wirelessnetworking, there is currently a great deal of interestin providing IP networking support for mobile hosts. Asa result of IPs reliance on the entire Internet address for host identification, most proposalsdepend on a default route through the mobile host's homeaddress, which makes for unnecessarily long routes. Thispaper introduces two concepts, localregion and patron service, based on thelocality features of host moving and calling patterns.It then shows how these concepts work together torealize a location management scheme for achievingoptimal routing for most traffic while restricting costlylocation propagation. The proposed scheme wasimplemented using a network simulator and evaluated fromrouting effectiveness point of view, as compared withits location overhead.     

Computing Optimal Diameter-Bounded Polygon Partitions

The minimum -small partition problem is the problem of partitioning a given simple polygon into subpolygons, each with diameter at most , for a given > 0. This paper considers the version of this problem that disallows Steiner points. This problem is motivated by applications in mesh generation and collision detection. The main result in the paper is a polynomial-time algorithm that solves this problem, and either returns an optimal partition or reports the nonexistence of such a partition. This result contrasts with the recent NP-completeness result for the minimum -small partition problem for polygons with holes (C. Worman, 15th Canadian Conference on Computational Geometry, 2003). Even though the running time of our algorithm is a polynomial in the input size, it is prohibitive for most real applications and we seek faster algorithms that approximate an optimal solution. We first present a faster 2-approximation algorithm for the problem for simple polygons and then a near linear-time algorithm for convex polygons that produces, for any > 0, an (+)-small partition with no more polygons than in an optimal -small partition. We also present an exact polynomial-time algorithm for the minimum -small partition problem with the additional constraint that each piece in the partition be convex.     

Nonlinear Versus Linear Learning Devices: A Procedural Perspective

We provide a discussion of bounded rationality learning behind traditional learning mechanisms, i.e., Recursive Ordinary Least Squares and Bayesian Learning . These mechanisms lack for many reasons a behavioral interpretation and, following the Simon criticism, they appear to be substantively rational. In this paper, analyzing the Cagan model, we explore two learning mechanisms which appear to be more plausible from a behavioral point of view and somehow procedurally rational: Least Mean Squares learning for linear models and Back Propagation for Artificial Neural Networks . The two algorithms look for a minimum of the variance of the error forecasting by means of a steepest descent gradient procedure. The analysis of the Cagan model shows an interesting result: non-convergence of learning to the Rational Expectations Equilibrium is not due to the restriction to linear learning devices; also Back Propagation learning for Artificial Neural Networks may fail to converge to the Rational Expectations Equilibrium of the model.     

Finding the Right Hybrid Algorithm – A Combinatorial Meta-Problem

Benchmark comparisons tend to overlook the most important challenge in solving combinatorial problems: how to design an appropriate algorithm. For example, an early version of Localizer incurred a factor 3 performance penalty when benchmarked against a C implementation of GSAT, but we would recommend implementing a new local search algorithm in Localizer rather than C every time. The ECLiPSe CLP language supports the experimental process of seeking the right hybrid algorithm for the problem at hand. It offers high-level modelling and control features, extensibility and a wide range of constraint solvers which can cooperate in the solving of a problem. We recently sought a new hybrid algorithm for a very unpromising class (SAT problems), and using ECLiPSe we were able to develop an algorithm which showed good performance on some very hard instances. We describe the process of exploring the space of hybrid algorithms for the problem class, and indicate the features of ECLiPSe that enabled us to find previously undiscovered algorithms. How to benchmark the solving of this meta-problem remains a topic of future research. We conclude by pointing out the advantages of an extensible platform, such as ECLiPSe, for developing sophisticated hybrid algorithms for large scale industrial combinatorial optimisation problems.     

Design by framework completion

An object-oriented framework in essence defines an architecture for a family of applications or subsystems in a given domain. Every application in the family obeys these architectural restrictions. Such frameworks are typically delivered as collections of inter-dependent abstract classes, together with their concrete subclasses. The abstract classes and their interdependencies implicitly realize the architecture. Developing a new application reusing classes of a framework requires a thorough understanding of the framework architecture.We introduce an approach called Design by Framework Completion, in which an exemplar (an executable visual model for a minimal instantiation of the architecture) is used for documenting frameworks. We propose exploration of exemplars as a means for learning the architecture, following which new applications can be built by replacing selected pieces of the exemplar. For the piece to be replaced, the inheritance lattice around its class provides the space of alternatives, one of these classes may be suitably adapted (say, by sub-classing) to create the new replacement.Design by Framework Completion proposes a paradigm shift when designing in presence of reusable components: It enables a much simpler top-down approach for creating applications, as opposed to the prevalent search for components and assemble them bottom-up strategy. We believe that this paradigm shift is essential because components can only be fitted together if they all obey the same architectural rules that govern the framework.     

An efficient steering control formulation for the articulated body mobile robot “KR-II”

This paper introduces an efficient steering control method for the articulated body mobile robot Koryu-II (KR-II). KR-II is a real robot, composed of six cylindrical segments linked in series and has a long snake-like appearance. The main issue on KR-II's steering control is, given from a remote human operator the velocity and orientation commands for the foremost segment, to automatically generate joint commands for all the following segments, such that they follow the foremost segment's trajectory. The derived method is based on a trajectory planning scheme in the inertial reference frame, and is feasible for real time computation. It also presents good energy efficiency and trajectory tracking performance characteristics, and can be extended for KR-II's W-Shaped Configuration steering control, which augments the lateral stability of the robot, essential for locomotion over uneven terrain. The validity of these methods are verified by experiments on the mechanical model KR-II.     

Regenerative simulation of response times in networks of queues: statistical efficiency

Summary This paper deals with the statistical efficiency of estimation methods for passage times in closed, multiclass networks of queues with priorities. Informally, a passage time is the time for a job to traverse a portion of the network. Such quantities are important in computer and communication system models, and in this context, quantities other than mean values are of interest. We consider here the efficiencies of the marked job method for passage time simulation (based on the tracking of a distinguished job) and the decomposition method in which observed passage times for all of the jobs enter in the construction of point and interval estimates. We show that the decomposition method is superior in that, for simulations of equal length, it produces tighter confidence intervals. We also calculate theoretical values for variance constants entering into central limit theorems used to obtain confidence intervals for mean passage times. These results provide a means of quantifying the relative efficiency of the decomposition method.     

Can organisations afford knowledge?

Affordance Theory has been widely discussed as a potential resource for the design of interfaces for CSCW and other systems. In this paper, we discuss the extension and adaption of this concept beyond the psychology of perception to the social distribution of a common stock of knowledge. We suggest that a working division of labour as that is known, oriented to, and rendered visible by the management of space and artifacts within a working environment can afford knowledge of organisational routines and practices. Learning to see the working division of labour is coming to understand the organisation. The grounds for extending the concept in this way are derived from consideration of an actual example taken from fieldwork. Some implications for the design of CSCW systems are reviewed.     

“陌生化”方法与动态广告受众的心理情感因素

利用俄国形式主义美学著名的"陌生化"理论方法进行设计成为一种社会必需。动态广告的"陌生化"特征日益彰显;同时,广大设计者利用"陌生化"予动态广告以相对陌生化和相对新鲜的审美体验。本文主要研究在动态广告当中"陌生化"方法对受众所产生的影响。以及动态广告受众的情感因素对动态广告设计的反作用。从而引领出如何抓住动态广告受众的情感倾向、"投其所好"、运用"陌生化"的原则进行动态广告设计。     

Constructing strongly convex approximate hulls with inaccurate primitives

The first half of this paper introducesEpsilon Geometry, a framework for the development of robust geometric algorithms using inaccurate primitives. Epsilon Geometry is based on a very general model of imprecise computations, which includes floating-point and rounded-integer arithmetic as special cases. The second half of the paper introduces the notion of a (–)-convex polygon, a polygon that remains convex even if its vertices are all arbitrarily displaced by a distance of of less, and proves some interesting properties of such polygons. In particular, we prove that for every point set there exists a (–)-convex polygonH such that every point is at most 4 away fromH. Using the tools of Epsilon Geometry, we develop robust algorithms for testing whether a polygon is (–)-convex, for testing whether a point is inside a (–)-convex polygon, and for computing a (–)-convex approximate hull for a set of points.