多个模指数运算的安全外包方案

模指数运算是公钥密码体制中的基本运算,但造价昂贵。可验证外包计算将用户的计算代价转移给服务器,能大大提高用户的计算效率,且能有效验证服务器的计算结果。我们利用指数之间的相互隐藏,提出了新的两个模指数运算外包方案,并推广到多个模指数运算。方案基于两个服务器,实现了模指数运算底数和指数的隐私性,并且用户的可验证概率接近于1。与已有方案相比,所提方案同时提高了用户的计算效率和外包结果的可验证概率。理论分析和仿真实验均表明,所提方案极大地降低了用户的计算代价。     

可验证的大规模矩阵满秩分解的安全外包

针对矩阵满秩分解的外包算法没有对原始矩阵中零元素的个数进行保护且没有对云返回结果的正确性进行验证的问题,提出了一个可验证的矩阵满秩分解的安全外包方案。首先,在加密阶段,结合Sherman-Morrison公式构造出一个稠密的可逆矩阵来进行加密。其次,在云计算阶段,一方面,要求云计算加密矩阵的满秩分解;另一方面,在得到满秩分解的结果（一个列满秩矩阵和一个行满秩矩阵）后,要求分别云计算列满秩矩阵的左逆和行满秩矩阵的右逆。接下来,在验证阶段,用户不仅要分别验证返回的两个矩阵是否满足行满秩和列满秩,还要验证这两个矩阵相乘是否等于加密矩阵。最后,如果验证通过,则用户可以利用私钥进行解密。在协议分析中,证明了所提方案满足正确性、安全性、高效性和可验证性。同时,当选择的原始矩阵的维度是512×512时,无论怎样改变矩阵中非零元素的密度,所提方案计算得到的加密矩阵的熵恒等于18,说明方案确实可以有效保护零元素的个数。实验结果表明所提方案具有较高的效率。     

安全可验证的行列式云外包计算及其电子交易方案

针对现有的云外包计算协议中服务端可能存在的用户信息被泄露、篡改等问题,提出了一个云环境下的安全、高效、可验证的矩阵行列式外包计算协议。首先,基于矩阵模糊技术构造云外包计算协议,它能够在不需要任何困难性假设的前提下保证用户信息的安全性;其次,通过构造一类特殊的变换矩阵对明文矩阵进行处理,使用户在收到返还结果后,能有效验证所反馈的计算结果是否被篡改,性能分析表明,此协议可以有效提高云外包计算的效率;最后,给出一个行列式外包计算的电子交易框架,能够有效应用于电子商务等领域。     

全委托的公共可验证的外包数据库方案

为解决可验证外包数据库方案存在的预处理阶段开销较大及不支持公共可验证的问题,提出了一个全委托的公共可验证的外包数据库模型.给出了模型的架构及交互流程,对模型进行了形式化定义,并给出了模型的正确性定义和安全性定义.利用双线性映射及可验证外包模幂运算协议,构建了一个全委托的公共可验证外包数据库方案,且给出了各个算法的详细描述,证明了方案的正确性和安全性.其安全性可规约为BDHE （bilinear diffie-hellman exponent）难题.与现有方案及不进行全委托计算的方案相比,全委托的公共可验证的外包数据库方案基于可验证外包模幂运算,将大量模幂运算外包给云处理,减小了数据拥有者的开销.理论与实验分析表明：该方案数据拥有者在预处理阶段所需的代价更低,效率更高,适于实际应用.此外,验证过程无需私钥参与,实现了公共可验证.     

隐私保护的高效可验证数据流协议

可验证数据流(verifiable data streaming, VDS)协议使得资源有限、计算能力不足的用户将爆炸式增长的数据外包到不完全可信的云服务器上,任意用户可以检索特定位置的数据并公开验证结果的正确性,不仅可以防止云端服务器篡改数据内容和对应位置,还允许数据拥有者有效更新已经外包的数据.然而,已有的可验证数据流协议没有考虑外包数据的隐私性,且用户添加新数据的复杂度与已存储数据的规模成对数关系,难以满足一些应用场景中对低延时和隐私保护的需求.本文构造了一个基于对称加密体制的新型变色龙认证树,对数据流先加密再存储,以此来保证数据的隐私性;依据通用的构造范式提出了新的支持隐私保护的高效可验证数据流协议,使得添加数据的计算开销达到了常量级,与已外包存储数据的规模无关.安全性和性能分析表明,所提出可验证数据流协议在标准模型下满足相应的安全性定义,且在隐私保护和计算开销方面具有优势.     

基于大规模矩阵Jordan分解的外包计算

目前,外包计算已成为减轻用户庞大计算量的重要策略之一。针对大规模矩阵的Jordan分解需要用户付出大量的计算资源问题。文章设计了一个安全、结果可验证、高效的外包协议,达到了节省用户计算资源的目的。通过线性变换、元素的重排列对原始矩阵进行加密,保护了用户隐私信息,并运用高效的验证算法对云端返回的结果进行了高效验证。文章通过计算复杂度分析,验证了该协议的高效性。     

云存储完整性验证密码学技术研究进展

云存储完整性验证技术允许用户将数据存储至云端服务器,并为用户提供可验证的完整性保证。典型的云存储完整性验证方案由两个阶段组成：一是数据处理阶段,用户使用私钥处理数据、生成可验证的元数据存储于云服务器,而本地只需保存与数据相关的一些参数,如密钥和数据标签等;二是数据完整性验证阶段,验证者通过和云服务器交互执行一个挑战/证明协议,能够以极高的概率判断出云端数据当前的完整性。到目前为止,已经涌现了大量的相关密码学方案。本文对可证明安全的可公开验证的云存储完整性验证关键密码学技术研究进展进行简要回顾,主要涵盖代理数据外包技术、代理完整性验证技术、基于身份的数据外包技术以及几种计算和通信效率优化技术等。     

支持属性撤销的可验证外包的多授权属性加密方案

针对云存储中基于多授权属性加密（MA-ABE）访问控制方案存在数据使用者解密开销大,同时缺乏有效属性撤销的问题,提出了一种支持属性撤销的可验证外包的多授权属性加密方案。首先,利用可验证外包技术,降低数据使用者的解密开销,同时验证数据的完整性。然后,利用双线性映射保护访问策略,防止数据拥有者身份泄露。最后,利用每个属性的版本密钥实现立即的属性撤销。安全性分析表明所提方案在标准模型中判定性的q双线性Diffie-Hellman指数假设下是安全的,同时满足了前向安全性和抗合谋攻击。性能分析表明所提方案在功能性和计算开销两方面都具有较好的优势,因此所提方案更适用于云存储下多授权属性加密环境。     

车联网中支持直接撤销的外包属性签名方案

数字签名在应对车联网中数据窜改威胁时扮演着重要作用,然而现有的签名方案面临着灵活性、效率、隐私保护、用户密钥管理等诸多问题,难以在车联网中释放潜力。针对这些问题,提出了一个面向车联网的直接可撤销外包属性签名方案。该方案使用了基于线性秘密分享的签名策略机制,赋予车联网用户在签名生成和验证方面的灵活性和隐私保护。此外,设计了一种高效的用户密钥直接撤销机制,以提供对用户的实时撤权。所提方案还构造了一种外包验证方法,从而显著降低了验证者的计算和存储开销。安全性分析结果表明,所提方案在选择消息攻击下具有不可伪造性,并且能够抵抗合谋攻击。实验结果表明了该方案相较于其他方案的优势及其在车联网中的实用性。     

高效完全可验证外包解密属性基加密方案

属性基加密虽然能够很好地保护用户的数据安全,但是用户解密的计算代价随着访问结构的复杂性而线性增加。外包解密技术的提出使得用户只需要很少的开销就能够解密得到明文。然而,外包解密技术是将大量的解密操作交由云服务器来处理,而云服务器通常被认为是半可信的。因此,对云服务器部分解密得到的转换密文进行正确性验证是很有必要的。本文提出一种高效的完全可验证外包解密属性基加密方案,使得授权用户以及非授权用户都能够实现转换密文正确性的验证。      

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.