LBS 中连续查询攻击算法及匿名性度量

k-匿名机制是LBS(location based service)中保证查询隐私性的重要手段.已有文献指出,现有的k-匿名机 制不能有效保护连续性查询的隐私性.提出一种连续查询发送模型,该模型融合了查询发送时间的间隔模型和连续性模型,针对此模型下的两种k-匿名算法Clique Cloaking 和Non-clique Cloaking,分别提出了一种连续查询攻击算 法.在此攻击算法下,匿名集的势不再适合作为查询匿名性的度量,因此提出一种基于熵理论的度量方式AD(anonymity degree).实验结果表明,对连续性很强的查询,攻击算法重识别用户身份的成功率极高;AD 比匿名集的势更能反映查询的匿名性.     

一种基于停止-转发MIX的统计型攻击

为了增强匿名系统的匿名性,更好地保护用户的通信臆私.基于停止-转发MIX提出一种新的统计型攻击算法.算法将攻击者的连续观察时间划分成t个周期,每个周期统计MIX节点输出信息包的接收者集合,称之为一个观察集合,获得t个观察集合后,采用概率统计、集合运算等方法,确定目标发送者的接收者集合.指出采用填充包技术防御该攻击时,可以增加攻击所需的观察集合数,降低攻击的有效性.     

基于期望值-混合熵的区间概率模糊随机多准则决策方法

定义了区间概率模糊随机变量及其期望值和混合熵.针对准则权重确知并且准则值为区间概率模糊随机变量的多准则决策问题,提出一种基于期望值-混合熵的决策方法.该方法首先给出了区间概率模糊随机变量的期望值-混合熵度量;然后基于此度量建立优化模型,通过计算得到各方案的期望值-混合熵区间;再采用可能度的方法得到方案集的排序.最后通过实例说明了该方法的有效性和可行性.     

概率不确定语言熵及其多属性群决策

针对概率不确定语言集的多个不确定语言术语和其概率各不相同的特点,提出基于概率不确定语言熵的多属性决策方法。定义四种新的概率不确定语言熵：模糊熵、犹豫熵、不完全信息熵和总熵,以分别测量概率不确定语言集的模糊性、犹豫性、信息不完全性和整体不确定性。给出了四种熵测度的公理化定义和表达式,根据概率不确定语言集的四种熵,构建能够解决属性权重未知的多属性决策模型,并通过案例和对比分析验证了该模型的有效性和合理性。     

基于匿名广播加密的云存储访问控制方法

针对现有的匿名广播加密方法在加解密性能和安全性方面的不足,提出一种基于拉格朗日插值多项式的匿名广播加密方法。首先定义了可以抵御自适应敌手攻击的匿名广播加密安全模型;然后在合数阶双线性群环境下采用拉格朗日插值多项式对方案进行了构建,在保证用户身份匿名性的同时,实现了高效的加解密;最后基于子群判定假设和合数阶判定双线性Diffie-Hellman假设,在标准模型下证明了方法针对自适应敌手具有密文的机密性和接收者匿名性。实验与性能分析表明,方法具有较低的通信和计算开销,可以有效地解决云存储中密文数据的匿名访问控制问题。     

一个标准模型下的匿名IBE方案

大多数基于身份的加密方案(Identity-based Encryption,IBE)不具备接收者匿名性.提出了一个匿名IBE方案,方案基于判定性双线性DH假设(Decisional Bilinear Diffie-Hellman,DBDH),对于选择明文攻击(Chosen Plaintext Attack,CPA)是安全的.最后,给出了方案正确性证明、匿名性分析以及安全性证明.方案的优势是加密过程不需要对运算、接收者匿名等.与Gentry的方案相比,本方案所基于的困难性问题更常见,弥补了DBDH假设下匿名IBE的空缺.     

基于期望值-混合熵的区间概率模糊随机多准则决策方法

定义了区间概率模糊随机变量及其期望值和混合熵.针对准则权重确知并且准则值为区间概率模糊随机变量的多准则决策问题,提出一种基于期望值-混合熵的决策方法.该方法首先给出了区间概率模糊随机变量的期望值-混合熵度量;然后基于此度量建立优化模型,通过计算得到各方案的期望值-混合熵区间;再采用可能度的方法得到方案集的排序.最后通过实例说明了该方法的有效性和可行性.

     

AGnutella:一种基于匿名的P2P文件共享机制

Gnutella是一种典型的纯分布式P2P文件共享网络系统,但在Gnutella中并没有考虑文件请求者和提供者的匿名需求.基于Gnutella提出了一种匿名的P2P文件共享机制AGnutella,文件请求者和文件提供者可以通过重路由的方式建立匿名路径,实现文件传输中的单向或双向匿名.对AGnutella的匿名性能以及传输性能进行了分析与测试,结果表明,AGnutella能够提供文件传输的双向匿名性,转发概率pf越大,匿名性越好.同时匿名文件传输的时延和重路由造成的网络负载也随pf增加而增加.匿名用户可以选取合适的pf值,在匿名性和延迟、网络负载之间进行平衡.     

电子投票匿名性分析

电子投票公布计票结果会影响投票者的匿名性。针对该问题,定义匿名性为投票选择的不确定度,利用熵衡量投票系统的投票者匿名性,比较计票结果公布前后投票者的匿名性变化。分析结果表明,投票规模越小,投票者匿名性在结果公布后受到的损失越大;在小规模电子投票情况下,计票结果应该选择只公布获胜者,不公布具体得票数,以减少投票者匿名的损失。     

基于可达概率区间的不确定决策树

针对不确定数据的概率分布难以获取的客观实际,讨论了缺失概率分布的值不确定离散对象的决策树。定义了(条件)概率区间,并证明了(条件)概率区间是可达概率区间;基于可达概率区间,定义了(条件)熵区间,并给出了求解(条件)熵区间的上/下界的方法;采用条件熵区间作为属性选择度量,提出了一种新的不确定决策树,将以0-1划分对象的决策树扩展到以概率区间分配对象的决策树,这样不仅可以处理缺失概率分布的值不确定离散对象,也可以处理确定离散对象。通过在基于UCI数据集的不确定数据集上的实验,证实了不确定决策树是有效的。     

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.