一种动态门限多组秘密共享方案

基于Shamir门限方案和RSA密码体制提出一种动态门限多组秘密共享方案。该方案中的多秘密分发者可根据所共享秘密的重要性,动态调整恢复该秘密时的门限值,使 组秘密根据不同的门限值在 个参与者中共享。方案可以灵活地增加或删除成员,无需更改其他成员的秘密份额。任何人可在秘密重构阶段验证每个合作的参与者是否进行欺诈,且无需专门的验证协议。     

Dominant speaker identification for multipoint videoconferencing

A multi-point conference is an efficient and cost effective substitute for a face to face meeting. It involves three or more participants placed in separate locations, where each participant employs a single microphone and camera. The routing and processing of the audiovisual information is very demanding on the network. This raises a need for reducing the amount of information that flows through the system. One solution is to identify the dominant speaker and partially discard information originating from non-active participants. We propose a novel method for dominant speaker identification using speech activity information from time intervals of different lengths. The proposed method processes the audio signal of each participant independently and computes speech activity scores for the immediate, medium and long time-intervals. These scores are compared and the dominant speaker is identified. In comparison to other speaker selection methods, experimental results demonstrate reduction in the number of false speaker switches and improved robustness to transient audio interferences.     

基于GACO的群智感知参与者选择方法研究

参与者选择方法作为群智感知研究的重要内容之一,现有研究还存在不足,只单一考虑任务发布时间或任务区域覆盖等属性,导致选择的参与者执行任务效率较差。因此针对这一问题综合考虑任务时间和任务区域覆盖等约束条件下,为实现任务执行效率最高和群智感知平台激励成本最少的优化目标,提出一种基于贪婪蚁群算法的群智感知参与者选择方法（PS-GACO）。该方法主要通过候选参与者聚集蚂蚁信息素浓度的多少准确选出适合执行发布任务的参与者,大大提高了任务执行效率。最后通过仿真实验将提出的PS-GACO方法与普通参与者选择方法进行比较,实验结果表明PS-GACO在算法运行时间、任务执行效率以及激励成本等方面都优于其他两种方法,对于群智感知参与者选择有很好的应用前景。     

A conference key agreement protocol with fault-tolerant capability

Secure communication is of utmost importance to participants of Internet conferences. Secure communication thwarts eavesdropping. In an Internet conference, all conference participants together establish a common conference key to enable multi-party and secure exchange of messages. However, malicious conference participants may try to obtain the conference key through unfair means, and this could result in the generation of different conference keys. This paper is intended as a proposal of a new form of conference key agreement protocol. It emphasizes the filtering of malicious participants at the beginning of the conference to ensure that all participants obtain the same conference key. The proposed method also has fault-tolerant capability. Efficiency and security of a protocol is important in practice. The security of the proposed protocol is based on discrete logarithm problem assumption. The protocol is executed in computationally secure environment. The secret information of a user cannot be determined from its corresponding public information and therefore ensures privacy. Since efficiency of a protocol depends on low computation cost, the protocol attempts to achieve lower computation cost without compromising on security.     

Approximate resolution of asynchronous conflicts among sequential collaborations in dynamic virtual environments

Asynchronous collaboration for a networked virtual environment (NVE) has emerged as a promising area in collaborative computer‐aided design applications. The concept of asynchronous collaboration is a sequential collaboration of temporal processes in an NVE where the participants are not required to be present at the time of the collaboration. Conflicts in asynchronous collaboration occur because the preceding task of a participant can influence the output of the ensuing task of another participant. The conflicted tasks must be modified manually. However, it requires considerable time and effort to resolve conflicts in a sequential collaboration. In this paper, we present an asynchronous collaborative framework that converts the conflict states of the shared objects into approximately resolved states. We develop a novel approximate resolution algorithm using a task‐based modeling mechanism to resolve the asynchronous conflicts with their corresponding tasks. Moreover, we propose a visual relation editor for convenient management. The participants can set flexible relations among shared objects using the proposed visual editor. The proposed approximate resolution approach can significantly reduce the average resolution time and the number of required manual task resolutions in a virtual environment compared to a manual resolution approach. Copyright © 2015 John Wiley & Sons, Ltd.     

Packet construction for secure conference call request in ad hoc network systems

In this paper, a packet construction mechanism using an ID-based factorial number structure (ID-based FNS) is proposed for a secure conference call system in an ad hoc network. We adopt the ID-based concept for a conference key generation in which each participant with one’s own public identity uses a pre-chosen secret-key to generate the exchange conference key for the conference call. Furthermore, due to the mobility of nodes in an ad hoc network environment, it is likely that some nodes quit or join during the operation of this conference. To solve these problems, we employ an information exchange table for each participant node in order to manage a secure conference call in an ad hoc network system. In addition, our scheme employs only one cryptographic algorithm of the secret-key system. The extraction of the secure sub-packets associated with each intended receiver is protected on the basis of the Diffie-Hellman key exchange protocol with the trusted public-key exchange. Therefore, the subsequent message recovery is successfully accomplished. This provides a new and feasible solution for a secure conference call in an ad hoc network system.     

动态防欺诈的多组秘密共享方案

基于离散对数及拉格朗日插值公式提出了一个动态防欺诈的多组秘密共享方案。在该方案中,m组秘密根据不同的门限值在n个参与者中共享,秘密份额由参与者自己选择,因而秘密分发者和参与者之间不需要维护安全信道,每个参与者可以在恢复阶段验证其他参与者是否进行了欺诈,每个参与者只需持有一个秘密份额就可以实现多组秘密的共享。方案的安全性基于离散对数问题的难解性。     

不同权限下自证实的多秘密共享方案

为了解决现有不同权限下秘密共享方案中子秘密的安全分发问题,利用双一元多项式,结合基于身份的公钥密码技术,提出一种新的基于不同权限的门限秘密共享方案,并给出其推广形式。该方案中,子秘密由秘密分发者和参与者分别生成,参与者的子秘密可反复使用,共享任意多个秘密。任何人可验证参与者身份和子秘密的合法性,有效防止参与者欺诈。分析表明,新方案不仅安全,而且效率也优于已有文献。     

基于Cluster态的可验证多方量子密钥协商方案

基于四量子比特Cluster态,提出一种可验证多方量子密钥协商方案.方案允许每次由两个参与者利用自己的子密钥分别在每个四量子比特Cluster态的两个粒子上执行X运算,并对转换后的Cluster态执行延迟测量,这保证了每个参与者对协商密钥的贡献相等.提出的方案使用相互无偏基粒子作为诱饵粒子,并且利用对称二元多项式的一对函数值对这些诱饵粒子执行酉运算,不仅可以进行窃听检验,而且还能进行参与者之间的身份验证.本方案适用于任意大于2的参与者人数.安全性分析表明,提出的方案能够抵抗外部攻击及参与者攻击.与现有的多方密钥协商方案相比,该方案不仅在诱饵粒子的使用上有优势,同时具有较高的量子比特效率.     

基于身份的会议密钥协商算法

利用Cha和Cheon提出的基于身份的数字签名方案,提出了一种新的会议密钥协商算法,并分析了该算法的正确性、安全性和执行效率。分析结果表明,在Gap Diffie-Hellman假设下,任何窃听者均无法得到有关会议密钥的任何信息,且无论存在多少恶意参与者,诚实参与者都能够协商出共同的会议密钥。该方案效率较高,有较强的灵活性、适应性和实用性。     

基于参与者权重的动态多秘密广义门限方案

针对现有参与者有权重的动态多重秘密广义门限方案的不足,基于中国剩余定理,提出一个参与者权重不同的 门限秘密共享方案。在该方案中,参与者的子秘密由参与者选取并保存,每个参与者的子秘密可以多次使用。分发者和参与者间不需要安全信道,系统可以灵活地增加或删除成员,且一次可以恢复多个秘密。分析结果表明该方案具有安全性和实用性。     

基于广义接入结构的可证实多秘密共享方案

针对当前多数秘密共享方案存在着增加或删除成员时必须重新计算其它成员的秘密份额等问题,提出了一个基于广义接入结构的高效的多秘密分享方案。在该方案中秘密管理者可高效地增加或删除成员,无须重新计算其它成员的秘密份额。此外,该方案不仅可高效地检测秘密管理者与参与者的欺诈行为,而且参与者可采用并行算法恢复子秘密。     

Satisfaction-based query replication

In large-scale Internet-based distributed systems, participants (consumers and providers) are typically autonomous, i.e. they may have special interests towards queries and other participants. In this context, a way to avoid a participant to voluntarily leave the system is satisfying its interests when allocating queries. However, participants satisfaction may also be negatively affected by the failures of other participants. Query replication is a solution to deal with providers failures, but, it is challenging because of autonomy: it cannot only quickly overload the system, but also it can dissatisfy participants with uninteresting queries. Thus, a natural question arises: should queries be replicated? If so, which ones? and how many times? In this paper, we answer these questions by revisiting query replication from a satisfaction and probabilistic point of view. We propose a new algorithm, called S _b QR, that decides on-the-fly whether a query should be replicated and at which rate. As replicating a large number of queries might overload the system, we propose a variant of our algorithm, called S _b QR+. The idea is to voluntarily fail to allocate as many replicas as required by consumers for low critical queries so as to keep resources for high critical queries during query-intensive periods. Our experimental results demonstrate that our algorithms significantly outperform the baseline algorithms from both the performance and satisfaction points of view. We also show that our algorithms automatically adapt to the criticality of queries and different rates of participant failures.     

A meeting scheduling problem respecting time and space

We consider the problem of determining suitable meeting times and locations for a group of participants wishing to schedule a new meeting subject to already scheduled meetings possibly held at a number of different locations. Each participant must be able to reach the new meeting location, attend for the entire duration, and reach the next meeting location on time. In particular, we give two solutions to the problem instance where each participant has two scheduled meetings separated by a free time interval. We present an O(n logn) algorithm for n participants obtained by purely geometrical arguments. Our second approach uses the concept of LP-type problems and leads to a randomized algorithm with expected running time O(n). We also consider a graph-based model where participants belong to different groups and can travel along the edges of a graph. For the meeting, only one member out of each group is required. The resulting problem can be solved using furthest color Voronoi diagrams on graphs.

A hybrid particle swarm optimization for a university course scheduling problem with flexible preferences

The timetabling problem at universities is an NP-hard problem concerned with instructor assignments and class scheduling under multiple constraints and limited resources. A novel meta-heuristic algorithm that is based on the principles of particle swarm optimization (PSO) is proposed for course scheduling problem. The algorithm includes some features: designing an ‘absolute position value’ representation for the particle; allowing instructors that they are willing to lecture based on flexible preferences, such as their preferred days and time periods, the maximum number of teaching-free time periods and the lecturing format (consecutive time periods or separated into different time periods); and employing a repair process for all infeasible timetables. Furthermore, in the original PSO algorithm, particles search solutions in a continuous solution space. Since the solution space of the course scheduling problem is discrete, a local search mechanism is incorporated into the proposed PSO in order to explore a better solution improvement. The algorithms were tested using the timetabling data from a typical university in Taiwan. The experimental results demonstrate that the proposed hybrid algorithm yields an efficient solution with an optimal satisfaction of course scheduling for instructors and class scheduling arrangements. This hybrid algorithm also outperforms the genetic algorithm proposed in the literature.     

加权门限秘密共享

提出了一种基于模运算的加权的门限秘密共享方案,当参与者的权重之和大于等于门限值时可以恢复秘密,而小于门限值时则不能.目前仅有的关于加权秘密共享方案都是基于分解结构的,其缺点是参与者需要掌握多个子秘密,并且各个子秘密使用场合不相同,管理和使用不太方便.方案中每个参与者只需要保存一个子秘密,简化了密钥管理与使用.该方案适用于强调管理方便性的环境.在某些情况下,还可以调整权重和门限参数来减小问题的规模,但达到的效果跟原来的系统一致,为此,提出了控制结构的等价性的概念,并提出了一种基于整数规划的参数调整算法.     

对基于单向函数的He-Dawson多步骤秘密共享方案的改进

在(t,n)门限秘密共享方案中,有n个参与者,至少t个参与者拿出自己的子秘密就能够同时重构m个秘密.He-Dawson提出了一个基于单向函数的多步骤秘密共享方案.但是他们的方案是一次方案而且不能抵抗合谋攻击.每个参与者的子秘密由参与者自己选取,所以不存在秘密分发者的欺骗.并且每个参与者能够验证其他合作者的欺骗.每个参与者选取的子秘密可以复用.并且组秘密可以以任意顺序重构.此方案还能够抵抗合谋攻击.本方案的安全是基于Shamir门限方案和RSA密钥体制.     

Occlusion points identification algorithm

In this paper a very simple and efficient algorithm is proposed, to calculate the invisible regions of a scene, or shadowed side of a body, when it is observed from a pre-set point. This is done by applying a deterministic numerical procedure to the portion of scene in the field of view, after having been projected in the observer reference frame. The great advantage of this approach is its generality and suitability for a wide number of applications. They span from real time renderings, to the simulation of different types of light sources, such as diffused or collimated, or simply to calculate the effective visible surface for a camera mounted on board of an aircraft, in order to optimize its trajectory if remote sensing or aerial mapping task should be carried out. Optimizing the trajectory, by minimizing at any time the occluded surface, is also a powerful solution for a search and rescue mission, because a wider area in a shorter time can be observed, particularly in situations where the time is a critical parameter, such as, during a forest fire or in case of avalanches. For its simplicity of implementation, the algorithm is suitable for real time applications, providing an extremely accurate solution in a fraction of a millisecond. In this paper, the algorithm has been tested by calculating the occluded regions of a very complex mountainous scenario, seen from a gimbal-camera mounted on board of a flying platform.     

一种动态的多秘密共享方案

基于Shamir的秘密共享体制和RSA加密算法的安全性,提出一种动态的门限秘密共享方案。在该方案中可以动态添加或删除参与者以及更新多重秘密,无需重新分发子秘密,参与者的秘密份额由每个参与者自己选取,其秘密份额的信息可以通过公开的信道发送给秘密分发者,在秘密恢复过程中,每个参与者能够验证其他参与者是否进行了欺骗。     

Social trend tracking by time series based social tagging clustering

Social tagging is widely practiced in the Web 2.0 era. Users can annotate useful or interesting Web resources with keywords for future reference. Social tagging also facilitates sharing of Web resources. This study reviews the chronological variation of social tagging data and tracks social trends by clustering tag time series. The data corpus in this study is collected from Hemidemi.com. A tag is represented in a time series form according to its annotating Web pages. Then time series clustering is applied to group tag time series with similar patterns and trends in the same time period. Finally, the similarities between clusters in different time periods are calculated to determine which clusters have similar themes, and the trend variation of a specific tag in different time periods is also analyzed. The evaluation shows the recommendation accuracy of the proposed approach is about 75%. Besides, the case discussion also proves the proposed approach can track the social trends.