The disagreement power of an adversary

At the heart of distributed computing lies the fundamental result that the level of agreement that can be obtained in an asynchronous shared memory model where t processes can crash is exactly t?+?1. In other words, an adversary that can crash any subset of size at most t can prevent the processes from agreeing on t values. But what about all the other ${2^{2^n - 1} - (n+1)}$ adversaries that are not uniform in this sense and might crash certain combination of processes and not others? This paper presents a precise way to classify all adversaries. We introduce the notion of disagreement power: the biggest integer k for which the adversary can prevent processes from agreeing on k values. We show how to compute the disagreement power of an adversary and derive n equivalence classes of adversaries.     

一种基于多传感器的噪声信号分离方法

分析了工业现场噪声分布情况和噪声的传输特性,提出了一种将多点多传感器测量所得噪声值,再通过相关性分析进行噪声分离的新方法.各个传感器的测量信号都是混叠噪声信号,它们的自相关函数的波形与信号本身的波形无关,仅与信号所包含的频率成分亦即振幅谱有关,且互相关函数rxy(n)也只包含信号Xn和Yn所共有的频率成分.理论分析和计算机仿真证明可以有效的分离强干扰噪声,为噪声故障诊断提供可靠的真实数据.     

一种新型高灵敏度双叠片式流体声发射传感器的研制

研制高灵敏度、安装使用方便、抗干扰能力强的传感器是实现刀具磨损在线监测的关键.参考空气声学中常用的压差式微音器的典型结构,考虑自动化加工中使用的要求,研制成功可用于刀具磨损状态监测的非接触高灵敏度双叠片式流体声发射传感器.对研制的流体声发射传感器性能进行了实验分析,结果表明传感器对刀具磨损产生的声发射信号具有较高的灵敏度.     

Path Clearance

In military scenarios, agents (i.e., troops of soldiers, convoys, and unmanned vehicles) may often have to traverse environments with only a limited intelligence about the locations of adversaries. We study a particular instance of this problem that we refer to as path clearance problem. In path clearance, an agent has to navigate to its goal as quickly as possible without being detected by an adversary. When picking a path to follow, the agent does not know the precise locations of adversaries. Instead, it has a list of their possible locations, each associated with the probability of containing an adversary. Any of these locations can be sensed by either the agent itself at a distance close enough (provided the agent has a capability of long-range sensing) or by one of the scouts (if they are available). If no adversary is present at a sensed location, the agent can then safely traverse through it. Otherwise, the agent has to take a detour.     

The Lazy Adversary Conjecture Fails

In the context of competitive analysis of online algorithms for the k-server problem, it has been conjectured that every randomized, memoryless online algorithm exhibits the highest competitive ratio against an offline adversary that is lazy, i.e., that will issue requests forcing it to move one of its own servers only when this is strictly necessary to force a move on the part of the online algorithm. We prove that, in general, this lazy adversary conjecture fails. Moreover, it fails in a very strong sense: there are adversaries which perform arbitrarily better than any other adversary which is even slightly "lazier."     

A new provably secure certificateless short signature scheme

Certificateless public key cryptography simplifies the complex certificate management in the traditional public key cryptography and resolves the key escrow problem in identity-based cryptography. In 2007, Huang et al. revisited the security models of certificateless signature scheme. They classified adversaries according to their attack power into normal, strong, and super adversaries (ordered by their attack power). Recently, Du and Wen proposed a short certificateless signature scheme and presented that their scheme is secure against the strong adversary in the random oracle model. In this paper, we show that their short signature scheme is insecure against the strong adversary. We then propose a new short certificateless signature scheme which is secure against the super adversary. Our scheme is the first certificateless signature scheme which satisfies both the strongest security level and the shortest signature length.     

Weakening the perfect encryption assumption in Dolev–Yao adversaries

We consider secrecy and authentication in a simple process calculus with cryptographic primitives. The standard Dolev–Yao adversary is enhanced so that it can guess the key required to decrypt an intercepted message. We borrow from the computational complexity approach the assumptions that guessing succeeds with a given negligible probability and that the resources available to adversaries are polynomially bounded. Under these hypotheses we prove that the standard Dolev–Yao adversary is as powerful as the enhanced one.     

Sound Tracing: Rendering Listener Specific Acoustic Room Properties

We present an acoustic rendering approach visualizing the listener‐specific contribution of frequency‐dependent pressure fields on a scene geometry with acoustic reflection and scattering properties. Our method facilitates the evaluation of simulated acoustics showing the effect of simulation parameters like absorption and scattering. The image‐based spatial localization of acoustic properties is complementary to the auditive evaluation by means of auralization. Our core contribution is a pressure‐based acoustic rendering equation and a corresponding raytracing method applying techniques from photorealistic rendering to the field of simulated room acoustics. Applications are directed at the visualization of interference patterns and analyzing the impact of acoustic reflection parameters.     

电磁分析环境下密码设备面向实际的安全性度量

为在充斥电磁分析旁路攻击敌手的危险环境下评估密码设备的安全性,通过将密码学标准黑盒模型中的敌手能力进行加强,在物理可观测密码术模型的框架内,定义了具有电磁泄漏信息分析能力的密钥恢复敌手与不可分辨性判定敌手。分别以敌手成功率定量度量与敌手优势定性度量,给出密码设备面向实际的安全性度量方式。通过成功率度量方式的实验,比较了几种不同电磁旁路分辨器的攻击能力,以便为进一步研究并开发可证明抵抗电磁分析攻击的密码系统和设备打下基础。     

一种IND-CCA2完全匿名的短群签名

基于线性假设下的Cramer-Shoup加密方案和SDH假设,提出一种新的SDH问题的零知识证明协议,并基于此协议构造了一种在Bellare-Micciancio-Warinshi模型下可证明安全的短群签名方案.该方案具有IND-CCA2完全匿名性,允许攻击者在攻击完全匿名性时提问打开预言机.签名的长度仅为1704bits.     

水下复杂声源结构自振特性分析

为解决水下复杂声源结构--潜艇的湿模态提取和扩展问题,用ANSYS非对称模态算法对其研究. 重点阐述浸没于水中的潜艇有限元建模方法,包括结构与流场的一体化单元划分、边界条件施加以及结构与流体耦合界面的处理等.通过仿真计算得到的潜艇湿模态和空气中干模态的分析结果,为潜艇外水域辐射声场预测提供重要参考依据.     

基于簇的传感器网络节点复制攻击检测

当传感器节点布置在敌方区域并遭到敌人捕获时,敌方有能力破解传感器节点而得到其中所存储的重要信息.敌人一旦掌握这些信息,便可以复制一系列这样的节点且将其布置到网络中为进一步开展攻击作准备,这种入侵活动被称为传感器网络节点复制攻击.节点复制不同于诸如路由攻击一类的外部攻击,它直接危害传感器节点,破坏力强,给网络带来严重影响.在现有的分布式检测方法基础上提出一种基于簇结构的传感器网络节点复制攻击检测方案.仿真实验表明,改进的方案能对节点复制攻击做出有效判断,而且传输开销较现有检测方案要小.     

Classifier evaluation and attribute selection against active adversaries

Many data mining applications, such as spam filtering and intrusion detection, are faced with active adversaries. In all these applications, the future data sets and the training data set are no longer from the same population, due to the transformations employed by the adversaries. Hence a main assumption for the existing classification techniques no longer holds and initially successful classifiers degrade easily. This becomes a game between the adversary and the data miner: The adversary modifies its strategy to avoid being detected by the current classifier; the data miner then updates its classifier based on the new threats. In this paper, we investigate the possibility of an equilibrium in this seemingly never ending game, where neither party has an incentive to change. Modifying the classifier causes too many false positives with too little increase in true positives; changes by the adversary decrease the utility of the false negative items that are not detected. We develop a game theoretic framework where equilibrium behavior of adversarial classification applications can be analyzed, and provide solutions for finding an equilibrium point. A classifier??s equilibrium performance indicates its eventual success or failure. The data miner could then select attributes based on their equilibrium performance, and construct an effective classifier. A case study on online lending data demonstrates how to apply the proposed game theoretic framework to a real application.     

无证书代理盲签名方案的安全性分析?

分析证明某无证书代理盲签名方案对于无证书密码体制的2类敌手都不安全。类型I敌手利用公钥替换攻击,可以伪造任意原始签名者对代理签名者的代理授权,或伪造任意合法代理签名者的代理盲签名。类型II敌手利用预选的目标用户生成含有陷门信息的系统参数后,可以伪造该目标用户对任意其他用户的代理授权,从而使非法代理签名者生成未经授权的代理盲签名。     

对一种无证书代理签名方案的分析与改进

分析了一种无证书代理签名方案,指出其针对于无证书密码系统中的两类敌手都不安全。类型I敌手可替换用户的公钥来伪造代理授权和代理签名;类型II敌手(KGC)可针对预先选择好的用户生成特殊的系统参数,然后伪造代理授权。为了克服这些安全问题,提出了一种改进的方案,分析表明,新方案具有更好的安全性。     

On the security of auditing mechanisms for secure cloud storage

Cloud computing is a novel computing model that enables convenient and on-demand access to a shared pool of configurable computing resources. Auditing services are highly essential to make sure that the data is correctly hosted in the cloud. In this paper, we investigate the active adversary attacks in three auditing mechanisms for shared data in the cloud, including two identity privacy-preserving auditing mechanisms called Oruta and Knox, and a distributed storage integrity auditing mechanism. We show that these schemes become insecure when active adversaries are involved in the cloud storage. Specifically, an active adversary can arbitrarily alter the cloud data without being detected by the auditor in the verification phase. We also propose a solution to remedy the weakness without sacrificing any desirable features of these mechanisms.     

Adversary Aware Surveillance Systems

We consider surveillance problems to be a set of system-adversary interaction problems in which an adversary can be modeled as a rational (selfish) agent trying to maximize his utility. We feel that appropriate adversary modeling can provide deep insights into the system performance and also clues for optimizing the system's performance against the adversary. Further, we propose that system designers should exploit the fact that they can impose certain restrictions on the intruders and the way they interact with the system. The system designers can analyze the scenario to determine conditions under which system outperforms the adversaries, and then suitably reengineer the environment under a “scenario engineering” approach to help the system outperform the adversary. We study the proposed enhancements using a game theoretic framework and present results of their adaptation to two significantly different surveillance scenarios. While the precise enforcements for the studied zero-sum ATM lobby monitoring scenario and the nonzero-sum traffic monitoring scenario were different, they lead to some useful generic guidelines for surveillance system designers.      

光纤声发射传感器的研究现状与展望

光纤声发射传感器是近年来出现的集光学、声学、电子学为一体的新型声发射传感器。介绍了光纤声发射传感器的原理、特点、研究现状和最新进展,以及各类传感器在不同领域的应用情况,提出了目前光纤声发射传感技术存在的问题、发展趋势与展望。     

声诱饵建模与仿真研究

随着水声技术的发展,水下武器对抗也日趋复杂.着重对水下武器中的声诱饵进行了声学特性的仿真研究,建立了声诱饵被动干扰、主动诱骗的仿真模型,并研究了海洋环境对声诱饵作用效果的仿真模型,并结合具体的仿真系统给出了一些仿真结论.该仿真研究可以为整个反鱼雷武器系统或舰载武器对抗鱼雷仿真系统提供仿真支持,为水声对抗仿真系统软件设计提供理论依据,从而对对抗器材的型号研制和战术使用具有一定的参考价值.     

Optimal Sensor Networks for Area Monitoring Using Rotating and Beam Sensors

We consider the problem of monitoring the Euclidean plane using rotating sensors with detection sectors and beam sensors. We assume that intruders can appear anywhere at any time and move arbitrarily fast, and may have full knowledge of the sensor network. We require that such intruders be detected within a finite amount of time. We give an optimal network for this problem consisting of a combination of rotating sensors of angle 0 and beam sensors that uses the minimum number of both types of sensors. We show a trade-off between the density of beam sensors needed and the angle of the detection sector of the rotating sensors. Secondly, we give a family of sensor networks using only rotating sensors for the same problem, that demonstrate a trade-off between the detection time and the density of rotating sensors used. We show that the density of rotating sensors required in this case can be significantly reduced by increasing the angle of detection sectors. Finally, we show that our results on the infinite plane can be used to derive sensor networks that monitor some finite regions using a density of sensors that is asymptotically the same, or close to that of the infinite plane case.