基于广播加密的会话密钥分配新方案

广播加密方案是一种应用广泛的群组安全通信方案,在付费电视、视频会议和无线传感网络等场合具有良好的应用前景.该文针对许多基于二叉树结构的方案在中心控制密钥量O(n)上作了一些改进,提出了一个安全的基于广播加密的会话密钥分配方案.新方案在中心密钥存储量上有明显的优势,同时能安全有效地完成密钥的分发、用户添加以及加密密钥更新等功能.     

基于BB84与椭圆曲线的数字签名方案

利用BB84协议在量子密钥分配过程中的安全性与椭圆曲线加密体制在经典加密算法中的优越性相结合,提出了一种基于BB84协议和椭圆曲线的数字签名方案,该方案利用量子密钥作为会话密钥从而使得签名过程高效、简易,此会话密钥在密钥分配过程中具备的可证明安全性与椭圆曲线加密体制的安全性相结合对该数字签名方案提供了双重安全保护,同时可以达到互相认证的效果。     

同余方程加密方案的研究

目前基于公钥的加密和会话密钥交换方案容易受到中间人攻击且效率不高。为此,提出了一种基于同余方程的加密和会话密钥交换方案,该算法可以安全高效地实现会话密钥的协商和加密消息的传输,并且还能防止中间人攻击。该方案在一定程度上防止第三者对传输消息的篡改,其安全性是建立在大数因子分解的困难性基础上的。     

椭圆曲线域的移动自组网密钥协商协议

为了有效解决移动自组网节点间安全通信的问题,提出了一种在椭圆曲线域的会话密钥动态协商方案.方案结合椭圆曲线数字签名技术、椭圆曲线加密体制,由参与会话的所有节点共同协商生成会话密钥,而会话密钥在会话结束后就作废.会话密钥的动态协商特性,以及椭圆曲线域的数字签名技术和加密算法的采用,使得方案在保证节点间会话过程安全性的同时,也减轻了节点的计算负担.方案具有抗中间人攻击、重放攻击和密钥独立性等安全特性,并具有一定的恶意节点发现的能力.     

基于身份的高效签密密钥封装方案

KEM-DEM 结构的混合密码体制是获得IND-CCA安全最实际有效的方法,传统的KEM由公钥加密方案实现,仅提供DEM使用的会话密钥的保密性安全.2005年Alexander等人将签密的概念与KEM-DEM结构的混合密码体制相结合,提出了Signcryption KEM-DEM结构的混合签密.其中Signcryption KEM是利用发送者私钥和接收者公钥共同生成会话密钥及其密钥封装.该方法可以使密钥封装同时具有保密安全性和不可伪造安全性.在基于身份密码体制上扩展了签密密钥封装的定义,结合Sakai-Kasahara私钥提取结构以及椭圆曲线上相关的困难问题给出了一个基于身份的签密密钥封装的实例方案,并在随机预言机模型下对该实例方案的安全性进行了证明.该方案具有ID-IND-CCA保密性安全和ID-UF-CMA不可伪造性安全.提出的实例方案在会话密钥封装阶段不需要进行对计算以及映射到点的Hash函数计算.通过有效的对优化计算和点压缩技术,本实例方案在具有高安全性的同时也具有执行性能上的优势.     

一种轻量级Web通信加密方案*

为保护用户Web通信安全,针对现有Web加密中的运算负荷问题,提出了可保护用户隐私的轻量级Web通信加密方案。该方案很大程度降低服务器在会话密钥协商时的运算负荷,实现通信业务流加密、抵抗第三方监控,进而有效保护用户隐私。     

基于共用密钥的高效多密钥同态加密方案研究

作为安全多方计算理想的实现方式之一，多密钥同态加密在抗量子攻击和便于构建安全多方计算方案上有显著优势。然而，现有的BGV型多密钥同态加密算法存在密钥计算复杂、密文尺寸大等问题。为此提出了一种使用单密钥同态加密方案构造多密钥同态加密方案，该方案将主要的运算部分用单密钥同态加密方案加密完成，在产生共用密钥和共同解密部分采用已有的多密钥同态加密完成。理论分析表明，该加密方案可以减小密钥尺寸，降低同态乘法复杂度，提高加密运算效率。     

一种基于SM9的可撤销标识广播加密方案北大核心CSCD

文章提出一种基于国密标识算法SM9的可撤销标识广播加密方案。该方案在SM9标识广播加密方案的基础上,结合可撤销广播加密方案,利用二叉树对用户进行权限管理,实现授权用户的撤销和加入。密钥生成中心利用二叉树为未被撤销的用户更新密钥,用户只能通过该密钥获得相应的会话密钥,从而解密广播密文并获得数据。文章在随机预言模型下证明了该方案满足选择明文攻击下的不可区分性。效率分析表明,该方案效率较高,具有较好的实用性。     

基于PKI体系的无线局域网认证方案研究

本文提出了一个基于公钥基础设施PKI体系的认证方案。实现了认证服务器对接入点AP的认证,在临时密钥的分发过程中,实现了全加密的分发,即认证服务器向AP和用户分发临时密钥都进行加密。同时提出了三级密钥体系机制,即私钥、会话密钥和临时密钥,实现了认证密钥和加密密钥的分离。     

支持属性撤销的可追踪外包属性加密方案

属性基加密是一种能够对云服务器中数据实现细粒度访问控制的新型公钥加密方法,但是属性基加密中密钥分配、数据加密和解密过程的计算开销过大,给资源受限的用户造成很大的计算负担.为解决该问题,构造了一个将密钥分配与解密工作外包给云服务器的支持属性撤销的属性加密方案,同时该方案可验证外包计算的正确性.该方案使用线上/线下加密,既有效保护用户数据的隐私性,又减少用户的计算开销,提升方案运行效率;其次方案中使用树形访问策略,以提供更加细粒度的访问控制;同时利用重加密的方法实现细粒度的属性撤销,通过生成重加密密钥更新属性与密文,间接撤销单个属性;最后将用户身份嵌入密钥,达到用户可追踪的性质,并在标准模型下证明该方案是选择明文的不可区分安全性.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.