Search

The stream ciphers RCR-64 and RCR-32 designed by Sekar et al. are the most recent additions to the Py-family of stream ciphers, originally designed by Biham et al. The ciphers are among the fastest stream ciphers on software. To the best of our knowledge, the only reported attacks on the ciphers are due to Ding et al. , published in the Journal of Universal Computer Science. In this paper, we review these alleged attacks on the RCR ciphers and show that they are based on non-existent keystream biases stemming from flawed probability calculations. [ABSTRACT FROM AUTHOR]

Artificial intelligence is one of the most trending topics in the field of Computer Science which aims to make machines and computers 'smart'. There are multiple diverse technical and specialized research associated with it. Due to the accelerating rate of technological changes, artificial intelligence has taken over a lot of human jobs and is giving excellent results that are more efficient and effective, than humans. However, a lot of time there has been a concern about the following: will artificial intelligence surpass human intelligence in the near future? Are computers' ever accelerating abilities to outpace human jobs and skills a matter of concern? The different views and myths on the subject have made it even a more than just a topic of discussion.   In this research paper, we will study the existing facts and literature to understand the true definitions of artificial intelligence (AI) and human intelligence (HI) by classifying each of its types separately and analyzing the extent of their full capabilities. Later, we will discuss the possibilities if AI eventually can replace human jobs in the market. Finally, we will synthesize and summarize results and findings of why artificial intelligence cannot surpass human intelligence completely in the future. [ABSTRACT FROM AUTHOR]

The mixing time of random walks on a graph has found broad applications across both theoretical and practical aspects of computer science, with the application effects depending on the behavior of mixing time. It is extensively believed that real-world networks, especially social networks, are fast mixing with their mixing time at most |$O(\log N)$| where |$N$| is the number of vertices. However, the behavior of mixing time in the real-life networks has not been examined carefully, and exactly analytical research for mixing time in models mimicking real networks is still lacking. In this paper, we first experimentally evaluate the mixing time of various real-world networks with scale-free small-world properties and show that their mixing time is much higher than anticipated. To better understand the behavior of the mixing time for real-world networks, we then analytically study the mixing time of the Apollonian network, which is simultaneously scale-free and small-world. To this end, we derive the recursive relations for all eigenvalues, especially the second largest eigenvalue modulus of the transition matrix, based on which we deduce a lower bound for the mixing time of the Apollonian network, which approximately scales sublinearly with |$N$|⁠. Our results indicate that real-world networks are not always fast mixing, which has potential implications in the design of algorithms related to mixing time. [ABSTRACT FROM AUTHOR]

Confidentiality, integrity and availability, while being key requirements for ensuring security, have had limitations in providing an integral security model that incorporates the benefits of all predominant designs. Heeding to the call that security models cater to unique operational characteristics of individual firms, this paper presents a deep structure framework of information systems (ISs) security. The framework incorporates three models—representational model, which identifies subsystems within an organization; state-tracking model, which ensures that different states trace IS security in the real world;nd the decomposition model, which defines specific external events that are a stimuli to changes in internal events. In a final synthesis, the paper presents a deep structure-based conceptual clarity that manifests the meaning of dynamic, custom-fit and flexible IS security solutions. [ABSTRACT FROM AUTHOR]

This paper examines three ideas: First, the traditional relationship between a science, the mathematics it uses and the engineering based on it. Second, the nature of (software) computer science, which may not be a science at all, and its unusual use of mathematics. And finally, the nature of software engineering, its relationship with computer science, and its use of mathematics called ‘formal methods’. These three ideas turn on the first of them, since the scientific world view seems natural for the study of computing. The paper's thesis is that while software touches science in many ways, it does not itself have a significant scientific component. For understanding programming, for teaching it and for applying it in the world, science is the wrong model. Mathematics has found its own foundations apart from science, and computer science must do the same. [ABSTRACT FROM AUTHOR]

Signposts make complex documents more flexible and easier to read; signposts exist in many forms, but are familiar as cross references and as hypertext links. Signposting systems need to be carefully designed, so that they are reliable, easy to use for readers yet convenient for authors to embed in their writing. There are fundamental problems in achieving good signposting, which this paper explores through cross-referencing in the popular medium of LaTeX, which is often the typesetting system of choice for heavily cross-referenced documents. This paper provides an implementation of cross references for LaTeX users. Problems with LaTeX and TeX arise, and are explored and mostly solved: some problems are due to the designs of these systems, but, crucially, some problems are unavoidable, an inevitable part of signposting in principle, whatever systems are used, even including the web. [ABSTRACT FROM AUTHOR]

A policy for a minimal reactive agent is a set of condition-action rules used to determine its response to perceived environmental stimuli. When the policy pre-disposes the agent to achieving a stipulated goal we call it a teleo-reactive policy. This paper presents a framework for constructing and evaluating teleo-reactive policies for one or more minimal agents, based upon discounted-reward evaluation of policy-restricted subgraphs of complete situation graphs. The main feature of the method is that it exploits explicit associations of the agent's perceptions with states. The framework allows to construct and evaluate policies for a number of cooperating agents by focusing upon the behaviour of a single representative of them. This abstraction ameliorates the potential combinatorial burden. Within the framework varied behaviours can be modelled, including communication between agents. Simulation results presented here indicate that the method affords a good degree of predictive power. The paper presents two different branch and bound algorithms used to optimize policy evaluation. [ABSTRACT FROM PUBLISHER]

Energy efficiency is increasingly important for future information and communication technologies (ICT), because the increased usage of ICT, together with increasing energy costs and the need to reduce green house gas emissions call for energy-efficient technologies that decrease the overall energy consumption of computation, storage and communications. Cloud computing has recently received considerable attention, as a promising approach for delivering ICT services by improving the utilization of data centre resources. In principle, cloud computing can be an inherently energy-efficient technology for ICT provided that its potential for significant energy savings that have so far focused on hardware aspects, can be fully explored with respect to system operation and networking aspects. Thus this paper, in the context of cloud computing, reviews the usage of methods and technologies currently used for energy-efficient operation of computer hardware and network infrastructure. After surveying some of the current best practice and relevant literature in this area, this paper identifies some of the remaining key research challenges that arise when such energy-saving techniques are extended for use in cloud computing environments. [ABSTRACT FROM PUBLISHER]

Due to the increasing scale and complexity of software products, software maintenance especially on bug resolution has become a challenging task. Generally in large-scale software programs, developers depend on software artifacts (e.g., bug report, source code and change history) in bug repositories to complete the bug resolution task. However, a mountain of submitted bug reports every day increase the developers' workload. Therefore, 'How to effectively resolve software defects by utilizing software artifacts?' becomes a research hotspot in software maintenance. Considerable studies have been done on bug resolution by using multi-techniques, which cover data mining, machine learning and natural language processing. In this paper, we present a literature survey on tasks, challenges and future directions of bug resolution in software maintenance process. Our investigation concerns the most important phases in bug resolution, including bug understanding, bug triage and bug fixing. Moreover, we present the advantages and disadvantages of each study. Finally, based on the investigation and comparison results, we propose the future research directions of bug resolution. [ABSTRACT FROM AUTHOR]

Reversible data hiding (RDH) algorithms are concerned with the recovery of the original cover image upon the extraction of the secret data. In some RDH algorithms, embedding and extraction are performed through modifying the histogram of prediction errors that are computed using certain predictors. However, the embedding capacity and image quality in these algorithms are dependent on the characteristics of a single predictor. In this paper, we propose the idea of employing multiple predictors in order to increase the embedding capacity. The idea of multiple predictors is integrated in the modification of prediction errors algorithm without adding any overhead regarding the predictor that is used for embedding at each pixel in the image. The selection of the accurate predictor depends on the polarity of the prediction errors from all predictors. Experimental results proved the efficiency of the proposed algorithm in terms of increasing the embedding capacity and producing competitive quantitative and qualitative quality of the stego image when compared with recent algorithms. [ABSTRACT FROM AUTHOR]

The prevalence of heterogeneous manycore processors has been shown as a promising alternative to web-based data parallel MapReduce applications. The differences of manycore from multicore raise new challenges to designing and implementing efficient and scalable MapReduce applications, such as memory access congestion. This paper argues that it is more efficient using multiple small groups of cores than using a single group with all cores to address these challenges. We propose a group-based MapReduce implementation, called Grouped-MapReduce (GMR). It uses grouping to align tasks so that the tasks in each group are congestion-free. Further, it uses multiplexing to control the implementation of groups so that multiple groups can efficiently share the limited memory bandwidth without causing serious memory access congestion. We have implemented a prototype of GMR based on Phoenix++, an already highly optimized MapReduce runtime. Experiments on six benchmarks show that GMR implements and scales well on manycore systems and obtains an impressive improvement over Phoenix++ from 1.04x to 1.77x without artificially tuning the existing application code. [ABSTRACT FROM AUTHOR]

To solve the problem of group task allocation with time constraints in open and dynamic network environments, this paper proposes a decentralized combinatorial auction-based approach for group task allocation. In the proposed approach, both resource providers and consumers are modeled as intelligent agents. The proposed approach is decentralized, so all the agents are limited to communicating with their neighboring agents. The proposed approach also allows agents to enter and leave the network environments freely, and is robust for the dynamism and openness of the network environments. Tasks in the proposed approach have deadlines, and may need the collaboration of a group of self-interested providers. The experimental results demonstrate that the proposed approach outperforms two well-known task allocation approaches in terms of success rate of task allocation, the individual utility of the agents, the speed of task allocation and scalability. [ABSTRACT FROM AUTHOR]

The motif discovery problem (MDP) is an important biological optimization problem that has been addressed in numerous ways. However, it is important to note that when we address real complex optimization problems, we should adequately formulate them in order to provide real applicability to the developed techniques. In the particular case of MDP, as we do not know the size of the motifs and the number of repetitions that can be found in the sequences, we must not make any length or pattern-repetition assumptions. In addition, if we consider that it is practically impossible to adequately formulate an optimization problem with a single-objective function formulation, multiobjective optimization can be a good methodology to be considered. In this paper, we propose a novel hybrid multiobjective algorithm for tackling the MDP. Our main objective is to study the results achieved by our algorithm, analysing its performance when different motif occurrence models are considered. As we will see, experimental results on different sets of real instances will point out the advantages and disadvantages of each model, also checking how a more realistic definition of the optimized problem provides better quality biological results. [ABSTRACT FROM AUTHOR]

IEEE 802.22 wireless regional area network (WRAN) is a cognitive radio-based network. WRANs are intended to be deployed by different service providers and designed to opportunistically utilize the unused TV bands. WRANs have to self-coexist with other overlapped WRANs in a distributed manner. Therefore, every service provider tries to acquire a band free of interference from others to satisfy a required quality of service. This self-coexistence problem is one of the major challenges in WRAN. In this paper, we propose a Markov-based distributed approach for mitigating this problem. We model the problem as an absorbing discrete-time Markov chain. In this model, if two or more overlapped WRANs select the same band, then each one should either stay or switch to another band according to a certain switching probability. This process continues until each one of the WRANs finds an interference-free band. In this case, the Markov chain reaches the absorbing state. This model is employed to find the optimal switching probability, which in turn minimizes the time required to reach the absorbing state. The switching probability is numerically found as a function of the number of overlapped WRANs and available bands. Extensive simulation has been conducted to validate our numerical results. [ABSTRACT FROM PUBLISHER]

Nowadays, networks are almost ubiquitous. In the past decade, community detection received an increasing interest as a way to uncover the structure of networks by grouping nodes into communities more densely connected internally than externally. Yet most of the effective methods available do not consider the potential levels of organization, or scales, a network may encompass and are therefore limited. In this paper, we present a method compatible with global and local criteria that enables fast multi-scale community detection on large networks. The method is derived in two algorithms, one for each type of criterion, and implemented with six known criteria. Uncovering communities at various scales is a computationally expensive task. Therefore, this work puts a strong emphasis on the reduction of computational complexity. Some heuristics are introduced for speed-up purposes. Experiments demonstrate the efficiency and accuracy of our method with respect to each algorithm and criterion by testing them against large generated multi-scale networks. This study also offers a comparison between criteria and between the global and local approaches. In particular, our results suggest that global criteria seem to be more robust to noise and thus more accurate than local criteria. [ABSTRACT FROM PUBLISHER]

While multi-label classification can be widely applied for problems where multiple classes can be assigned to an object, its effectiveness may be sacrificed due to curse of dimensionality in the feature space and sparseness of dimensionality in the label space. As a solution, this paper presents two alternative methods, namely Dependent Dual Space Reduction and Independent Dual Space Reduction, to reduce dimensions in the dual spaces, i.e. the feature and label spaces, using singular value decomposition (SVD). The first approach constructs the cross-covariance matrix to represent dependency between the features and labels, projects both of them into a single reduced space, and then performs prediction on the reduced space. On the other hand, the second approach handles the feature space and the label space separately by constructing a covariance matrix for each space to represent feature dependency and label dependency before performing SVD on dependency profile of each space to reduce dimension and for noise elimination and then predicting classes using their reduced dimensions. A number of experiments show that prediction on the reduced spaces for both dependent and independent reduction approaches can obtain better classification accuracy as well as faster computation, compared with the prediction using the original spaces. Finally, the results of our methods are also compared with the prediction using other types of dimensionality reduction, with consideration of the factors of covariance and threshold selection. [ABSTRACT FROM PUBLISHER]

This special issue includes research papers related to a workshop held at the Royal Society on 21st of September 2010, honouring Erol Gelenbe on his 65th birthday. The workshop brought together some 40 participants including some of Erol's former and current PhD students, colleagues and friends with whom he has interacted over the years, both in Europe and the USA. The papers focus on probability models in computer science, at the core of the field of computer performance engineering, which Erol pioneered. [ABSTRACT FROM AUTHOR]

Linkable ring signatures have found many attractive applications. One of the recent important extensions is a linkable threshold ring signature (LTRS) scheme. Unfortunately, the existing LTRS schemes are only secure in the random oracle model (ROM). In this paper, we make the following contributions. First, we construct the first LTRS scheme that is secure without requiring the ROM. Further, we enhance the security of a threshold ring signature (for both linkable or non-linkable) by providing a stronger definition of anonymity. This strengthened notion makes threshold ring signature schemes more suitable in real life. Finally, we provide efficient schemes that outperform the existing schemes in the literature. Our scheme is particularly suitable for electronic commerce or electronic government where anonymity and accountability are the most concerned factors. [ABSTRACT FROM PUBLISHER]

Loiss is a new byte-oriented stream cipher designed in 2010. It takes a 128-bit initial key and a 128-bit initial vector (IV) as inputs, and provides 128-bit-level security claimed by the designers. In this paper, we find a differential characteristic with significant probability over the full initialization of Loiss. Based on this differential characteristic, two differential key recovery attacks on Loiss are proposed. The first attack has a computational complexity of2123.61, requiring two related keys, 234.16 chosen IVs and 239.16 keystream bytes. The second attack is based on the first attack: reducing the computational complexity at the cost of increased data complexity. The second attack has a computational complexity of 264, requiring two related keys, 236.26 chosen IVs and 241.26 keystream bytes. The result shows that our second attack is much better than a brute force attack, and then Loiss does not provide 128-bit-level security. Furthermore, a new proposal for the initialization of Loiss is proposed. The modified Loiss keeps the basic structure of Loiss and provides enough resistance against our attacks on the original Loiss. Based on our security analysis, we conjecture that no attacks lower than brute force are possible on the modified Loiss stream cipher. [ABSTRACT FROM AUTHOR]

There are various ways to measure the shape difference between two n-node rooted binary trees (binary trees for short). A rotation on a binary tree is a local restructuring that changes the tree into another one preserving the in-order sequence. The rotation distance between two binary trees is the minimum number of rotations needed to transform one into another. Till now, no polynomial–time algorithm exists for computing the rotation distance between any two binary trees. Recently, Lucas (Comput. J., 47, 259–269, 2004) presented an O(n2)–time algorithm for finding the rotation distance between two binary trees, where the source tree is a degenerate tree and the destination tree is an angle tree. This paper improves the time-complexity to O(n) under this constraint. [ABSTRACT FROM AUTHOR]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM AUTHOR]

Composing large enterprise applications from reusable software components has become a major software development technique. Components are considered as black boxes and are composed together by their provided and required services. In comparison to other software development approaches, this allows for rapid development, clean and explicit architectures, and easy component reuse. Currently, there are several systems that support development and composition of components: service component architecture and Fractal are two well-known ones. At first sight, both have the same goals and provide very similar means to developers. In this paper, we briefly present both systems and then we focus on an in-depth comparison and evaluation of them. [ABSTRACT FROM AUTHOR]

This paper presents new algorithms for generating all n-node t-ary trees in linked representation which take constant average time per tree. They use fewer memory references and are considerably faster than previous such algorithms. [ABSTRACT FROM AUTHOR]

Applications of modal logics are abundant in computer science, and a large number of structurally different modal logics have been successfully employed in a diverse spectrum of application contexts. Coalgebraic semantics, on the other hand, provides a uniform and encompassing view on the large variety of specific logics used in particular domains. The coalgebraic approach is generic and compositional: tools and techniques simultaneously apply to a large class of application areas and can, moreover, be combined in a modular way. In particular, this facilitates a pick-and-choose approach to domain-specific formalisms, applicable across the entire scope of application areas, leading to generic software tools that are easier to design, to implement and to maintain. This paper substantiates the authors’ firm belief that the systematic exploitation of the coalgebraic nature of modal logic will not only have impact on the field of modal logic itself but also lead to significant progress in a number of areas within computer science, such as knowledge representation and concurrency/mobility. [ABSTRACT FROM AUTHOR]

This paper studies semantic efficiency measures for ambient intelligence. We follow an agent-based approach and investigate how large quantities of information can be efficiently handled. We will show how to dynamically set up a communication network between agents, which aims to minimize the communication load. The approach is based on a formal ontological notion of informativeness, on quantitative measures such as information gain and on the proper use of interaction mechanisms such as Publish/Subscribe. We also present experimental results that were obtained using our prototyping tool called Ubismart. [ABSTRACT FROM PUBLISHER]

In this paper we discuss the use of the social concept ‘conviviality’ for computer science in general, and for the development of ambient technologies in particular. First, we give a survey of the use of the concept ‘conviviality’ in the social sciences. Conviviality is usually considered a positive concept related to sociability. However, further analysis reveals a negative side related to lack of diversity, privacy and ethical issues. Second, we argue that conviviality requirements for ambient intelligence are challenging, because ambient technologies give rise to a new virtual and social reality, and conviviality issues play a central role in applications that are concerned with the interaction of material, virtual and social realities. Conviviality highlights an important challenge that we illustrate with examples that emphasize ethical issues, such as privacy threats, surveillance of users and identity theft. Intelligent interfaces, for example, allow instant interactions and thereby create strong needs for coordination and regulation mechanisms that have to be addressed to ensure the safeguard of individuals against abuses, such as privacy intrusions and identity manipulations. Third, we propose a conviviality ontology by operationalizing the fuzzy concept of ‘conviviality,’ such that it can be used in computer science in the same way as other social concepts such as ‘service,’ ‘contract’ or ‘trust’ are used in this area. Conviviality is defined using dependence networks, and tools for conviviality are based on, what we call, conviviality masks. Fourth, we illustrate how convivial ambient intelligence applications can be designed using our operationalized concept of conviviality. We illustrate our arguments and contributions with a running example on the use of ambient technologies in digital cities, as a prototypical example where material reality such as ambient technologies interacts with virtual and social realities. [ABSTRACT FROM PUBLISHER]

Sensor networks (SNs) consist of spatially distributed sensors which monitor an environment, and which are connected to some sinks or backbone system to which the sensor data is being forwarded. In many cases, the sensor nodes themselves can serve as intermediate nodes for data coming from other nodes, on the way to the sinks. Much of the traffic carried by SNs will originate from routine measurements or observations by sensors that monitor a particular situation, such as the temperature and humidity in a room or the infrared observation of the perimeter of a house, so that the volume of routine traffic resulting from such observations may be quite high. When important and unusual events occur, such as a sudden fire breaking out or the arrival of an intruder, it will be necessary to convey this new information very urgently through the network to a designated set of sink nodes where this information can be processed and dealt with. This paper addresses the important challenge by avoiding the routine background traffic from creating delays or bottlenecks that impede the rapid delivery of high priority traffic resulting from the unusual events. Specifically we propose a novel technique, the ‘Randomized Re-Routing Algorithm (RRR)’, which detects the presence of novel events in a distributed manner, and dynamically disperses the background traffic towards secondary paths in the network, while creating a ‘fast track path’ which provides better delay and better quality of service (QoS) for the high priority traffic which is carrying the new information. When the surge of new information has subsided, this is again detected by the nodes and the nodes progressively revert to best QoS or shortest-path routing for all the ongoing traffic. The proposed technique is evaluated using a mathematical model as well as simulations, and is also compared with a standard node by a node priority scheduling technique. [ABSTRACT FROM PUBLISHER]

As power dissipation causes thermal issues in cooling costs, lifetime and reliability, thermal management has become an important issue in today's OS and processor design. Early OS-level thermal management schemes were proposed and evaluated mainly with simulators or analytical models. In this paper, we implement a thermal-aware round-robin scheduling algorithm in the Linux kernel, and compare its performance with the ‘Heat-and-Run’ algorithm and the default Linux baseline scheduler on an Intel Core 2 Duo processor using representative benchmarks from SPEC2000, MiBench and NetBench. Our results indicate that the current Linux scheduler can easily be enhanced with thermal-awareness to show improved performance in terms of both the on-chip temperature condition and application throughput. [ABSTRACT FROM PUBLISHER]

In the design of power-aware on-demand routing protocols in mobile ad hoc networks, it must be taken into account that nodes may use a great amount of power to find the desired routing path during the path-discovery phase. In addition, in previous research on power-aware routing protocols, the path bandwidth was often not considered. In this paper, we tackle these issues by proposing a power-aware routing protocol with low route requests (LRR) to find a path with high path bandwidth. By making a low number of routing requests (RREQs), mobile nodes help to broadcast the routing request only when they first receive the routing requests. In addition, based on the receipt of the routing requests from the neighboring nodes, mobile nodes record the location information of its one-hop neighboring nodes. In the path-reply phase, mobile nodes in the found path use the collected location information of their neighbors and our proposed relay model to modify the found path so that the found path has high bandwidth. In our simulation, we compared our proposed routing protocol (LRR) with ad hoc on-demand distance vector, dynamic source routing and min–max battery capacity routing in terms of the following: power consumption in the path-discovery phase and the path-reply phase, bandwidth of the found path, power consumed during data transmission and overall power consumption. In addition, we compared our two proposed routing protocols, the minimum power consumption routing protocol that selects one path with minimum transmission power from all paths and the LRR routing protocol, in terms of the following: the power consumption in the path-discovery phase, the path bandwidth and the overall power consumption. From the simulation results and the analysis, we can see that the proposed LRR routing protocol that uses a low number of routing requests and our proposed relay model to improve path bandwidth can efficiently reduce the overall power consumption. [ABSTRACT FROM PUBLISHER]

In this paper, we introduce a new side-channel attack using block cipher cryptanalysis named a meet-in-the-middle attack. Using our new side-channel technique we show that advanced encryption standard (AES) with reduced 10 masked rounds is broken, which is faster than the exhaustive key search attack. This implies that one has to mask the entire rounds of the 12-round 192-bit key AES to prevent our attacks. Our result is the first one to analyse AES with reduced 10 masked rounds, while the previous best known side-channel attack is on AES with reduced eight masked rounds. [ABSTRACT FROM PUBLISHER]

Secure multicast provides efficient delivery which includes an identical data from a source to multiple receivers. A common solution is to apply a symmetric key that is used to encrypt the transmitted data. However, the heavy cost of the rekeying process is the main problem in large and dynamic multicast groups. The tree-based architecture is widely used to reduce the rekeying cost in terms of storage, transmission and computation. However, it usually requires extra overhead to keep key tree balance which is in order to achieve logarithmic rekeying cost. In this paper, we shall propose a new RSA-like multicast key management scheme to solve the rekeying problem. Our protocol applies a star-based architecture to eliminate the rekeying processes and provide the good performance when the membership changes in a multicast group. Furthermore, we also provide an extended multicast scheme, in which we combine public-key and symmetric-key cryptosystems to enhance the performance of multicast encryption. [ABSTRACT FROM PUBLISHER]

The identity (ID)-based public-key system using bilinear pairings defined on elliptic curves offers a flexible approach to simplify the certificate management. In 2006, the IEEE P1363.3 committee has defined the ID-based public-key system with bilinear pairings as one of public-key cryptography standards. In this, an authenticated key agreement (AKA) protocol is one important issue that provides mutual authentication and key exchange between two parties. Owing to the fast growth of mobile networks, the computational cost on the client side with low-power computing devices is a critical factor in designing an AKA protocol suited for mobile networks. In this paper, we present an efficient and secure ID-based mutual authentication and key exchange protocol using bilinear pairings. Performance analysis and experimental data are given to demonstrate that our proposed protocol is well suited for a client–server environment with low-power mobile devices. In comparison with the recently proposed ID-based protocols, our protocol has the best performance on the client side. [ABSTRACT FROM PUBLISHER]

Let G(V, E) be an undirected connected graph, where each vertex v is associated with a positive cost C(v) and each edge e = (u, v) is associated with two positive weights, W(u → v) and W(v → u). We consider a new graph problem, called the edge-orientation problem (the EOP). The major issue is to assign each edge e = (u, v) an orientation, either from u to v, denoted as u → v, or from v to u, denoted as v → u, such that maxx∈V{C(x) + Σx→z W(x → z)} is minimized. This paper first shows that the EOP is NP-hard on split graphs and planar graphs. Then, a linear-time algorithm on star graphs is proposed by the prune-and-search strategy. Finally, the algorithmic result on star graphs is extended to trees and simple cactus graphs using the dynamic programming strategy. [ABSTRACT FROM AUTHOR]

This special issue focuses on Discovery Science (DS), which is a scientific discipline on any discovery process that is mainly approached by computer science. DS first started as a national project in Japan involving more than 100 researchers in 1998 and the project gave birth to a series of international conferences on DS, which have been held successfully every year since 1998. The objective of this special issue is to provide a leading forum for timely, in-depth presentation of recent advances in algorithms, theories and applications in the field of DS. Seven papers, ranging in a spectrum from basic theoretical research to solid application research, are included in this special issue. [ABSTRACT FROM PUBLISHER]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM AUTHOR]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM AUTHOR]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM AUTHOR]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring the content to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM AUTHOR]

This special issue contains four papers selected from the 26th UK Performance Engineering Workshop (UKPEW), which was held during 8–9 July 2010 in the Department of Computer Science at the University of Warwick. UKPEW is the leading UK forum for the presentation of work relating to all aspects of performance modelling and the analysis of computer and telecommunication systems. This year's selected papers demonstrate the variety of topics on offer at UKPEW: performance issues in cloud computing, energy-aware routing in packet networks, source location privacy and multi-hop ad hoc networks for wireless networks. [ABSTRACT FROM AUTHOR]

Affordance is a widely used term in human–computer interaction (HCI) that, while familiar and attractive, does not have a clear operational definition. Using the mathematical concept of symmetry, this paper shows that it is possible to begin developing an operational definition for significant aspects of affordance by forming the theoretical concept of symmetry-affordance. The proposed definition restricts symmetry-affordance to particular contexts but in doing so makes it more useful, as it is clear how to exploit symmetry to aid design. The definition is in standard mathematics (in fact, group theory and model theory) and requires little additional structure. In examining symmetry-affordance, it becomes clear that some other HCI notions can be similarly interpreted by symmetry. The paper provides examples and design insights. Symmetry, as wide or as narrow as you may define its meaning, is one idea by which man through the ages has tried to comprehend and create order, beauty, and perfection. Hermann Weyl [(1952) Symmetry, Princeton University Press, Princeton, NJ] [ABSTRACT FROM AUTHOR]

There has been much interest in testing from finite-state machines (FSMs). If the system under test can be modelled by the (minimal) FSM N then testing from an (minimal) FSM M is testing to check that N is isomorphic to M. In the distributed test architecture, there are multiple interfaces/ports and there is a tester at each port. This can introduce controllability/synchronization and observability problems. This paper shows that the restriction to test sequences that do not cause controllability problems and the inability to observe the global behaviour in the distributed test architecture, and thus relying only on the local behaviour at remote testers, introduces fundamental limitations into testing. There exist minimal FSMs that are not equivalent, and so are not isomorphic, and yet cannot be distinguished by testing in this architecture without introducing controllability problems. Similarly, an FSM may have non-equivalent states that cannot be distinguished in the distributed test architecture without causing controllability problems: these are said to be locally s-equivalent and otherwise they are locally s-distinguishable. This paper introduces the notion of two states or FSMs being locally s-equivalent and formalizes the power of testing in the distributed test architecture in terms of local s-equivalence. It introduces a polynomial time algorithm that, given an FSM M, determines which states of M are locally s-equivalent and produces minimal length input sequences that locally s-distinguish states that are not locally s-equivalent. An FSM is locally s-minimal if it has no pair of locally s-equivalent states. This paper gives an algorithm that takes an FSM M and returns a locally s-minimal FSM M′ that is locally s-equivalent to M. [ABSTRACT FROM AUTHOR]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM PUBLISHER]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM PUBLISHER]

Digital forensics is a recently emerged research area, and it has attracted the attention of computer professionals, law enforcement experts and practitioners. It is a multidisciplinary area that includes multiple fields, i.e. law, computer science, finance, networking, data mining and criminal justice. We believe that papers enclosed in this Special Issue will enhance knowledge in digital forensics and will stimulate further research in the important areas of information and network security. [ABSTRACT FROM PUBLISHER]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM AUTHOR]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM PUBLISHER]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring it to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM AUTHOR]

Test coverage is sometimes used to measure how thoroughly software is tested and developers and vendors sometimes use it to indicate their confidence in the readiness of their software. This survey studies and compares 17 coverage-based testing tools primarily focusing on, but not restricted to, coverage measurement. We also survey features such as program prioritization for testing, assistance in debugging, automatic generation of test cases and customization of test reports. Such features make tools more useful and practical, especially for large-scale, commercial software applications. Our initial motivations were both to understand the available test coverage tools and to compare them to a tool that we have developed, called eXVantage (a tool suite that includes code coverage testing, debugging, performance profiling and reporting). Our study shows that each tool has some unique features tailored to its application domains. The readers may use this study to help pick the right coverage testing tools for their needs and environment. This paper is also valuable to those who are new to the practice and the art of software coverage testing, as well as those who want to understand the gap between industry and academia. [ABSTRACT FROM AUTHOR]

A program mode is a regular trajectory of the execution of a program that is determined by the values of its input variables. By exploiting program modes, we may make worst-case execution time (WCET) analysis more precise. This paper presents a novel method to automatically find program modes and calculate the WCET estimates of programs. First, the modes of a program will be identified automatically by mode-relevant program slicing, and the precondition will be calculated for each mode using a path-wise test data generation method. Then, for each feasible mode, we show how to calculate its WCET estimate for modern reduced instruction set computer (RISC) processors with caches and pipelines and for traditional complex instruction set computer (CISC) processors. We also present a method to obtain the symbolic expression for each mode for CISC processors. The experimental results show the effectiveness of the method. [ABSTRACT FROM AUTHOR]

The Capsule Reviews are intended to provide a short succinct review of each paper in the issue in order to bring to a wider readership. The Capsule Reviews were compiled by Fairouz Kamareddine. Professor Kamareddine is an Associate Editor of The Computer Journal and is based in the Department of Mathematical and Computer Sciences at Heriot-Watt University, Edinburgh, UK. [ABSTRACT FROM AUTHOR]