基于异或自反性与射频指纹的无线组播密钥生成方法

随着物联网技术的发展, 组播通信的需求日益增大。异或加密作为最简单高效的加密方法之一, 在信息安全方面有着广泛的应用。本文针对组播通信安全需求, 设计了一种基于异或自反性和射频指纹的组密钥生成方法。为解决多个终端在密钥生成过程中的传输资源选择冲突问题, 提出基于扩频和公私钥密码体系的用户标识方法。先利用射频指纹对用户认证, 并在组播用户间形成密钥随机源; 然后, 利用异或的自反特性实现分布式密钥生成。将射频指纹与公私钥密码体系结合, 不仅为射频指纹的识别结果提供了参考, 还为组播通信下密钥协商时的通信资源选择提供了方法。为评估射频指纹识别的影响, 提出并实验验证了一种基于时频分析与深度学习的射频指纹识别算法。最后, 分析了所提方法的密钥生成率、资源选择冲突和密钥生成效率,展示了所提方法的可行性和有效性。分析发现所提方法相比于传统方法, 分布式的密钥源使得密钥生成效率随着节点数的增大而提高。对组密钥被攻破概率的窃听模型仿真结果表明, 在生成同样长度的密钥时, 与遍历搜索密钥空间比较, 基于窃听者遍历搜索设备射频指纹特性的条件, 破解所提方法组密钥的复杂度要高出一至四个数量级, 验证了本文方法的安全性。     

基于物理层密钥的消息加密和认证机制

针对传统高层消息认证存在密钥泄露隐患、物理层消息认证无法防止被动窃听的问题,提出一种基于无线物理层特征的消息加密和认证机制。通过提取无线信道特征生成物理层密钥,并与身份密钥结合生成种子密钥;随后根据提取的种子通过密钥流生成器产生密钥流对消息进行加解密,对传输数据的私密性进行保护;最后接收方通过 CRC 校验结果对接收消息的真实性、完整性进行认证。仿真结果表明,该方法在防止被动窃听和主动攻击上具有更好的性能,密钥流随机性显著提高,认证漏检率降低约12。     

无线平坦衰落信道的密钥生成速率研究

针对传统窃听信道模型中假定合法信道完全互易、窃听方只处理合法双方一方信号的问题,对传统的窃听信道模型进行了改进.一方面引入相关系数ρ0来刻画合法信道的互易程度,另一方面考虑窃听方能够获取并利用合法双方的信息.在此基础上,推导得到了密钥生成速率的解析表达式,并对影响密钥生成速率的因素进行了仿真分析.仿真结果表明,密钥生成速率随合法信道的相关系数ρ0、信噪比γ的增大而增大,随合法信道与窃听信道之间的相关系数ρ1、ρ2的增大而减小.     

基于部分假名ID的RFID系统密钥无线生成算法

针对现有无线射频识别系统密钥生成算法中WiKey算法存在的安全与成本问题,提出了一种改进的基于部分假名ID的RFID系统密钥无线生成算法。在后向信道也可被窃听的情况下,加入部分假名ID信息以减少其他信息引入,并在一定程度上防止标签真实标识信息泄露;利用异或运算和双向认证机制对秘密数据进行加密传输及验证,使算法可以抵抗主动、被动攻击。最后,通过三种不同情况下的GNY逻辑证明和安全与性能分析表明算法的可行性。     

基于纠缠的BB84协议仿真研究

将传统的量子密钥分发协议与纠缠光子对的纠缠特性相结合,提出了一种改进的BB84协议--基于纠缠的BB84协议.为了考察该协议的可行性,利用量子计算语言分别针对协议的正确性和安全性进行了仿真验证,并进一步考察衰落信道对协议工作的影响.仿真结果显示:理想情况下,协议安全工作时密钥生成效率为14/30,接近理论值50%;在存在第三方窃听时,其密钥生成效率仅为5/30,远远小于50%,由此通信双方可以判断出第三方窃听存在.由于信道衰落的影响,实际密钥生成效率远远低于理论值.得出结论:基于纠缠的BB84协议也是绝对安全可靠、切实可行的量子密钥分发协议;为提高密钥生成效率,应尽量减小信道衰落.最后,对协议的应用进行了展望.     

一种基于BB84协议的量子密钥分配改进方案

针对BB84协议对存在窃听的有噪信道中进行量子密钥分配效率不高的问题, 提出一种改进方案。新方案在发送方与接收方都加入类似签名的过程, 能够很好地判断窃听的存在, 并且窃听者只能获取少量的密钥信息, 在保障传输过程安全的同时, 提高了量子密钥分配的效率。     

结合混沌和遍历矩阵的彩色图像密码

提出了一种基于混沌和遍历矩阵的彩色图像密码算法。首先,利用离散混沌映射生成整数遍历矩阵,利用遍历矩阵在空域分别实现彩色图像三基色置乱。然后,结合像素扩散操作和三维混沌序列分别对彩色图像三基色通道实施两轮逐像素加密。从统计特性、密钥敏感性、差分分析和密钥空间等诸方面对算法的安全性进行了分析。各种分析结果表明,该算法具有良好的像素值混淆、扩散和统计分布特性;密钥空间大而足以抵抗强力攻击;表明所提出的方案具有良好的实用性。     

基于位运算的RFID系统密钥无线生成算法

为了解决标签与读写器之间的共享密钥事先设置好而存在的安全缺陷问题,提出了一种基于位运算的共享密钥无线生成算法。算法采用无线生成密钥的方式,将读写器与标签产生的随机数通过位运算函数进行加密,最终动态生成两者之间的共享密钥,从而可以使共享密钥不用事先设置。通过全面的性能及安全性分析,表明该算法不仅能够确保标签及读写器端的计算量与原算法计算量相当,而且能够解决原算法中存在的安全缺陷问题。     

一种优化的组密钥协商算法smart-GDH

组密钥协商完成在一组成员之间协商密钥,从而有效地保护组内通信。密钥协商能够保证即使有第三方在对本密钥协商有着全面的了解和能够窃听到了所有通信过程的消息,也不能计算出这个密钥。目前有许多成熟的算法,文章中介绍了一种优化的GDH组密钥协商算法smart-GDH。     

基于激活标志位的改进RFID密钥无线生成算法

针对现有三种常见无线射频识别密钥无线生成场景下,设计的相应密钥生成算法中存在的算法理论证明缺失、重放攻击、密钥伪造攻击以及RFID标签身份ID泄露的安全性问题,设计了更安全的基于激活标志位的改进RFID系统密钥无线生成算法。改进算法仅基于多种超轻量级位运算来组合构建安全的算法框架、降低成本和提高效率;利用激活标志位AckBit机制以及新鲜性机制抵抗重放、密钥伪造攻击;通过完整GNY逻辑证明过程与安全性对比进行分析,证明了目标算法的安全可行性。最后,给出原算法与改进算法之间的标签成本代价对比,表明改进的算法在满足低成本的条件下具有更高的安全性。     

On the number of components in cooperating distributed grammar systems

It is proved that the number of components in context-free cooperating distributed (CD) grammar systems can be reduced to 3 when they are working in the so-called sf-mode of derivation, which is the cooperation protocol which has been considered first for CD grammar systems. In this derivation mode, a component continues the derivation until and unless there is a nonterminal in the sentential form which cannot be rewritten according to that component. Moreover, it is shown that CD grammar systems in sf-mode with only one component can generate only the context-free languages but they can generate non-context-free languages if two components are used. The sf-mode of derivation is compared with other well-known cooperation protocols with respect to the hierarchies induced by the number of components.     

认知无线电中能效优先的频谱感知算法研究

频谱感知是认知无线电的关键技术之一.针对认知无线电中降低频谱感知能耗的问题,研究了在满足一定感知性能的前提下,能效优先的频谱感知算法.首先对感知能耗最小化问题进行了建模,然后推导出目标检测概率与最小感知能耗之间的关系,接着给出了在目标检测概率要求下的最小感知能耗,最后分别对单信道和多信道场景进行了仿真,仿真结果验证了理论推导的正确性.     

A novel and effective image encryption algorithm based on chaos and DNA encoding

In this paper, we proposed a novel and effective image encryption algorithm based on Chaos and DNA encoding rules. Piecewise Linear Chaotic Map (PWLCM) and Logistic Map are applied to generate all parameters the presented algorithm needs and DNA encoding technology functions as an auxiliary tool. The proposed algorithm consists of these parts: firstly, use PWLCM to produce a key image, whose pixels are generated by Chaos; Secondly, encode the plain image and the key image with DNA rules by rows respectively and different rows are encoded according to various rules decided by logistic map; After that, employ encoded key image to conduct DNA operations with the encoded plain image row by row to obtain an intermediate image and the specific operation executed every row is chosen by logistic map; Then, decode the intermediate image as the plain image of next step. Finally, repeat steps above by columns again to get the ultimate cipher image. The experiment results and analysis indicate that the proposed algorithm is capable of withstanding typical attacks and has good character of security.     

The effect of the crystallization of indium tin oxide on indium tin oxide wet etching based on gate line with the structure of copper/indium tin oxide

In thin film transistor-liquid crystal display (TFT-LCD), the copper/indium tin oxide (Cu/ITO) layer was often used to be gate line. In this event, the patterning of ITO is necessary and important. However, the high temperature generated during Cu deposition will cause ITO to crystallize, which is not conducive to ITO etching. In this paper, the ITO films prepared by radio frequency (RF) magnetron sputtering were annealed according to the monitoring results of production line to simulate and study the effect of crystallization on the etching properties of ITO film. When the annealing temperature was less than 200°C, no large size grains were detected in ITO films, and the ITO films could be easily etched by etchant. However, the ITO films transformed from amorphous structure to polycrystalline structure after being annealed more than 200°C. After wet etching experiments, the polycrystalline ITO films could be hardly removed by etchant. The X-ray photoelectron spectroscopy (XPS) results showed that high temperature annealing induced a large amount of Sn⁴⁺ on ITO films surface. The Sn⁴⁺ was difficult to be dissolved by acid under normal conditions, which might be the most important factors that led to the greatly decreased etching rate for polycrystalline ITO films.     

动态阈值的双门限协作感知方法

随着通信技术的提高和通信应用的增多,无线频谱资源越来越匮乏.许多分配到资源的主用户利用率很低,认知无线电技术希望没有分配到资源的次用户合理使用主用户频谱来提高频谱的利用率.频谱感知技术关系到认知无线电中次用户对空闲频谱的使用机会,是认知无线电的关键技术之一.就是在已有的感知技术的基础上,提出了新的感知手段.在认知无线电网络中,不同的次用户由于与主用户距离以及自身所处环境的噪声影响不同,它们的信噪比一般是不一样的.这里采用的动态阈值的双门限协作感知方法,是对传统双门限能量感知方法的改进,通过充分考虑次用户之间的差异性来提高感知的性能.首先,根据对检测和虚警概率的要求,过滤掉一部分检测能力不满足条件的次用户.同时,每个次用户的用于能量感知的双门限会根据它们各自信噪比的不同而动态变化.通过与单门限能量感知以及传统双门限能量感知方法进行比较,可以看出本文提出的感知方法一定程度上提高了系统整体感知的性能.     

Scattered context grammars that erase nonterminals in a generalized k-limited way

A scattered context grammar erases nonterminals in a generalized k-limited way in a successful derivation, where k is a positive integer, if in every sentential form of a derivation, each of its substrings consisting of nonterminals from which the grammar derives empty strings is of length k or less. This paper demonstrates that if a scattered context grammar generates its sentences in this way, it can be converted to a scattered context grammar without erasing productions; in general, however, this is not possible.     

深度学习算法在问句意图分类中的应用研究

在聊天机器人多轮对话中如何根据上下文理解用户的意图是多轮交互中的一个重点问题，也是一个难点问题。现有的问句理解方法大多是针对单句的，且侧重于某种句式结构的理解。如何根据上下文语境对当前用户的意图进行识别，而不仅仅是针对单轮进行一个个分析，使得对话在一个连续的语境下具备细粒度的理解能力，是一个亟待解决的问题。针对以上问题，提出了一种基于深度学习的自然语言问句多意图分类方法，其中涉及到的用户意图包含闲聊类、音乐类、新闻类、算术类、餐饮类、订票类、天气类、服务类等13类。首先使用自然语言处理的相关技术对多轮对话进行处理分析，识别出其中的关键词，然后使用深度学习方法和分层分类技术构建了二分类和多分类深度学习模型，学习上下文语境和语义关系，共同对用户意图进行识别。通过实验证明了构建的深度学习模型对用户意图识别的准确率分别为94.81%、93.49%。因此，所提方法基本能够解决自然语言问句意图识别的问题。     

Die Zeitkomplexität des Normalisierungsproblems bei kontextsensitiven Grammatiken

Zusammenfassung Sei G eine kontextsensitive Grammatik. G^c bezeichne den kontextfreien Kern von G. In dieser Arbeit wird die Zeitkomplexität des folgenden Problems untersucht. Das NormalisierungsproblemSei ein Ableitungsbaum bezüglich G^c; ist auch ein Ableitungsbaum bezüglich G? Es wird gezeigt, daß im allgemeinen das Normalisierungs-problem NP-vollständig ist. Andererseits gibt es zu jeder kontextsensitiven Sprache L eine kontextsensitive Grammatik G, für welche das Normalisierungsproblem in Polynomzeit lösbar ist.

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The time complexity of the normalization problem of contextsensitive grammars

Summary Let G be a Contextsensitive grammar. G ^cf represents the context free core of G. In this paper the time complexity of the following problem will be discussed. The Normalization ProblemLet be a derivation tree with respect to G^c; is also a derivation tree with respect to G? It is shown that in general the normalization problem is NP-complete. On the other hand, for every context sensitive language L there is a corresponding context sensitive grammar G for which this normalization problem is solvable in polynomial time.

     

Congestion, Dilation, and Energy in Radio Networks

We investigate the problem of path selection in radio networks for a given static set of n sites in two- and three-dimensional space. For static point-to-point communication we define measures for congestion, dilation, and energy consumption that take interferences among communication links into account. We show that energy-optimal path selection for radio networks can be computed in polynomial time. Then we introduce the diversity g(V) of a set V ⫅ ℝ^d for any constant d. It can be used to upper bound the number of interfering edges. For real-world applications it can be regarded as Θ(log n). A main result is that a c-spanner construction as a communication network allows one to approximate the congestion-optimal path system by a factor of O(g(V)²). Furthermore, we show that there are vertex sets where only one of the performance parameters congestion, dilation, and energy can be optimized at a time. We show trade-offs lower bounding congestion × dilation and dilation × energy. The trade-off between congestion and dilation increases with switching from two-dimensional to three-dimensional space. For congestion and energy the situation is even worse. It is only possible to find a reasonable approximation for either congestion or energy minimization, while the other parameter is at least a polynomial factor worse than in the optimal network.     

Manual test case derivation from UML activity diagrams and state machines: A controlled experiment

ContextIt is a difficult and challenging task to fully automatize model-based testing because this demands complete and unambiguous system models as input. Therefore, in practice, test cases, especially on the system level, are still derived manually from behavioral models like UML activity diagrams or state machines. But this kind of manual test case derivation is error-prone and knowing these errors makes it possible to provide guidelines to reduce them.ObjectiveThe objective of the study presented in this paper therefore is to examine which errors are possible and actually made when manually deriving test cases from UML activity diagrams or state machines and whether there are differences between these diagram types.MethodWe investigate the errors made when deriving test cases manually in a controlled student experiment. The experiment was performed and internally replicated with overall 84 participants divided into three groups at two institutions.ResultsAs a result of our experiment, we provide a taxonomy of errors made and their frequencies. In addition, our experiment provides evidence that activity diagrams have a higher perceived comprehensibility but also a higher error-proneness than state machines with regard to manual test case derivation. This information helps to develop guidelines for manual test case derivation from UML activity diagrams and state machines.ConclusionMost errors observed were due to missing test steps, conditions or results, or content was written into the wrong field. As activity diagrams have a higher perceived comprehensibility, but also more error-prone than state machines, both diagram types are useful for manual test case derivation. Their application depends on the context and should be complemented with clear rules on how to derive test cases.