基于数字承诺的区块链交易金额保密验证方法

传统区块链交易中,隐私保护都是在匿名机制下加密用户的敏感信息,引入公正的第三方对交易明文信息进行验证,然而一旦第三方受到攻击,用户的交易信息便会被泄露,且在理性状态下不存在真正公正的第三方.为了能够更好地解决区块链交易中存在的隐私问题,针对交易者非匿名状态下的交易金额保密验证问题,采用PVC数字承诺协议,将交易金额隐藏在承诺中,并构造公开可验证的零知识证明方案,使验证者能在不获取交易敏感信息的情况下对交易的合法性进行保密验证.同时,利用椭圆曲线同态加密特性加密金额,进而解决交易者密文账本的更新问题.对所提出的隐私保护方案的正确性进行验证和分析,结果表明,与已有方案相比,所提方案具有计算复杂度相对较低、安全性强、高效等优点.     

基于群签名和同态加密的联盟链双重隐私保护方法

区块链账本公开,以实现交易的溯源与可验证,但账本的透明使得区块链用户的隐私成为一个亟待解决的问题.为了解决联盟链交易中的交易金额和身份的隐私暴露问题,提出了基于群签名和同态加密的联盟链双隐私保护方法,在满足交易溯源和可验证的前提下,实现收付款者身份和交易金额的隐私保护.将群签名中群的概念与联盟链恰当结合,并提出一种部分身份匿名的概念,使方案能够满足对其他交易节点匿名,同时确保主要节点可验证.并利用Paillier同态加密的加同态性质验证交易的合法性,保护交易金额的隐私.提出主要节点的4步验证方法,通过对群签名、账户所属权和交易金额合法性的验证,实现主要节点对交易合法性的监管.通过分析,该方案可以抵抗篡改攻击和公钥替换攻击,且交易合法性验证合理,最后,通过与其他方案的对比分析,该方案的计算开销是合理的.     

大零币匿名技术及追踪技术综述

近年来,依托于区块链技术的研究取得了重大突破且发展快速,各种数字货币正在不断兴起并涌入市场.大零币作为到目前为止区块链UTXO模型中隐私性最强的币种,其匿名技术除了为用户自身隐私提供了有力保障之外,同样具有很高的科研价值和广泛的应用前景.因此,为了规范数字货币的合法使用,探寻数字货币匿名技术更广泛的应用前景,各界学者也都在大零币匿名与反匿名技术方面进行了不同角度的研究.聚焦于大零币这一新型数字货币,首先介绍了大零币这一币种的大体框架;其次对大零币采用的匿名技术——zk-SNARKs和屏蔽池交易技术进行了梳理;然后总结并分析了目前各界学者在大零币追踪技术方面的研究;最后对大零币匿名技术和追踪技术的发展进行了展望.     

区块链中可监管的身份隐私保护方案

在账本公开、多方共识情况下确保交易身份的隐私保护是区块链技术面临的主要挑战之一.目前公有链中基于匿名认证和交易混淆的身份隐私保护方案由于缺乏监管又难于在行业应用中推广.借鉴门罗币中的身份隐私保护方案,引入监管方的角色,基于一次性地址加密和零知识证明设计了可监管的交易接收方身份隐私保护方案;结合可链接环签名和可撤销环签名设计了可链接可撤销环签名方案,以实现基于自主混淆的可监管交易发送方身份隐私保护方案.基于上述方案,系统在保护交易方身份隐私的同时,还支持监管方可离线恢复交易参与方的真实身份,从而达到“可控匿名”的监管目的.分析和测试结果表明,方案设计的算法运算时间均为毫秒级,可满足区块链非高频交易场景下的性能需求.     

一种基于AdaBoost模型的区块链异常交易检测方案

针对区块链系统加密货币交易记录中存在的盗币异常行为,文章基于Ada Boost模型提出一种具有隐私保护功能的异常交易检测方案。该方案采用加法同态加密和矩阵混淆技术,在有效识别并预测异常交易的同时,保证交易数据的隐私性。此外,在云外包环境中设计实现方案的底层协议,并证明了方案的正确性和隐私保护性质。与同类协议相比,该方案在保证隐私性的同时,具有较高的检测准确率和召回率,平均每条记录的检测时间为毫秒级,适用于真实加密货币交易的检测场景。     

基于纳什谈判的共享经济区块链网络PoS共识传播博弈分析

针对共享经济中的信任问题,利用区块链技术搭建基于PoS(权益证明)共识机制的共享经济区块链网络,实现去信任化和去中心化.在Po S共识机制中,区块链用户提供交易费用,从而激励矿池招募验证者进行区块传播验证,区块链用户与矿池都能从更多的验证者数量中获益,但验证者越多,双方付出的成本越高.首先,从纳什谈判的角度研究共享经济区块链网络PoS共识机制中区块链用户与矿池的利益冲突问题,在交易费用与验证者数量之间进行权衡,构建纳什谈判博弈模型;然后,证明区块链用户与矿池的纳什谈判博弈模型中纳什谈判解的存在性和唯一性,得到区块链用户和矿池的最优决策;最后,通过数值算例分析通信成本和验证者数量对区块链用户和矿池的最优决策以及效用的影响.研究结果表明:区块链用户与矿池都能从较低的通信成本中获益;纳什谈判博弈模型能够有效解决共享经济区块链网络中用户与矿池的利益冲突,提高网络效率.     

一种基于联盟链的物联网匿名交易方案

针对物联网终端交易的跨平台、去中心化、隐私、安全需求,提出基于联盟链的匿名交易方案,确保用户身份隐匿。通过划分基础域和互联域实现中心化身份认证和去中心化交易;对身份认证,提出基于Merkle树的双因素认证方案,实现各节点身份与消息的去耦;针对通信中明文消息暴露用户身份问题,提出基于CoinJoin思想的聚合签名隐私保护方案,混淆交易身份,以抵抗身份关联分析攻击;最后针对一致性和记账权问题,提出基于信誉评价策略的共识机制。安全性与效率分析表明,所提方案能以较低存储和计算开销保护终端身份隐私。     

TTShuffle：一种区块链中基于两层洗牌的隐私保护机制

区块链隐私保护技术中的去中心化混币机制CoinJoin和CoinShuffle,分别因为代理节点不可信和节点需要层层传递加密而存在安全或效率低的问题,因此提出了TTShuffle,一种两层的隐私保护机制。首先将所有混币节点分成不同的组,通过层层加密在组内进行第一层洗牌,保护组内交易的敏感数据;然后由每个组派一个节点作为本组的代表,进行第二层的组间洗牌,保护所有组的敏感数据得到最后完整的交易内容。通过安全和实验分析表明,TTShuffle中40个混币参与者混币时间低于10 s,相比CoinShuffle机制提高了混币的效率,减少了混币时间,也确保了混币过程的隐私安全。     

基于加密分割的位置隐私保护方法

基于位置的服务(location-based services,LBS)由于存在隐私泄露问题已越来越成为隐私保护领域中的热点.针对用户协作的隐私保护方法无法为参与用户提供自定义匿名度功能,且对协作用户的隐私保护效力不足,提出了一种基于加密分割的位置隐私保护方法.该方法采用分布式结构,通过用户对查询信息进行分割、加密、交换混合,满足了用户自定义匿名度需求,提高了用户间的隐私安全性,同时,采用假名方法抵御长期统计的攻击方式.通过理论分析和实验结果表明所提出的方法具有较好的隐私保护效果.     

基于可追踪环签名的联盟链身份隐私保护方法

作为目前被广泛使用的一种区块链,联盟链相较于公有链虽然具有更好的隐私性,但也仍然面临着因去匿名化方法而导致用户身份隐私泄露的问题。为了保护联盟链中用户的身份隐私,并且增加系统的容错性,提出了将可追踪环签名和实用拜占庭容错结合的联盟链身份隐私保护方法。该方法的核心思想是通过可追踪环签名来使联盟链中用户的身份具有条件匿名性,条件匿名性指的是用户在一定条件下是匿名的,即用户在正常交易时是匿名的,而当用户之间产生交易纠纷时,也可以对交易相关用户的身份进行去匿名化。此外,将可追踪环签名与实用拜占庭容错相结合,去匿名化的任务由联盟链中的节点通过实用拜占庭容错完成,减少了联盟链中心机构的权利和责任,即使用户对中心机构具有匿名性,也保证系统在中心机构出错时能够正常运行。通过实验分析和对比,该方案能够在合理的计算开销内保护用户身份隐私,并且保证较高的安全性和容错性。     

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.