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The purpose of this article is to improve detection of common movement. Detecting if two or multiple devices are moved together is an interesting problem for different applications. However, these devices may be aligned arbitrarily with regards to each other, and the three dimensions sampled by their respective local accelerometers can therefore not be directly compared. The typical approach is to ignore all angular components and only compare overall acceleration magnitudes – with the obvious disadvantage of discarding potentially useful information.

This paper contributes a method to analytically determine relative spatial alignment of two devices based on their acceleration time series. The method uses quaternions to compute the optimal rotation with regards to minimizing the mean squared error.

Based on real-world experimental data from smartphones and smartwatches shaken together, the paper demonstrates the effectiveness of the method with a magnitude squared coherence metric, for which an improved equal error rate (EER) of 0.16 (when using derotation) over an EER of 0.18 (when not using derotation) is shown.

After derotation, the reference system of one device can be (locally and independently) aligned with the other, and thus all three dimensions can consequently be compared for more accurate classification.

Without derotating time series, angular information cannot be used for deciding if devices have been moved together. To the best of the authors ' knowledge, this is the first analytic approach to find the optimal derotation of the coordinate systems, given only the two 3D time acceleration series of devices (supposedly) moved together. It can be used as the basis for further research on improved classification toward acceleration-based device pairing.

Spatial messaging is a direct extension to text and other multi‐media messaging services that have become highly popular with the current pervasiveness of mobile communication. It offers benefits especially to mobile computing, providing localized and therefore potentially more appropriate delivery of nearly arbitrary content. Location is one of the most interesting attributes that can be added to messages in current applications, including gaming, social networking, or advertising services. However, location is also highly critical in terms of privacy. If a spatial messaging platform could collect the location traces of all its users, detailed profiling would be possible – and, considering commercial value of such profiles, likely. The purpose of this paper is to present Air‐Writing, an approach to spatial messaging that fully preserves user privacy while offering global scalability, different client interface options, and flexibility in terms of application areas.

The authors contribute both an architecture and a specific implementation of an attribute‐based messaging platform with special support for spatial messaging and rich clients for J2ME, Google Android, and Apple iPhone. The centralized client/server approach utilizes groups for anonymous message retrieval and client caching and filtering, as well as randomized queries for obscuring traces.

Two user studies with 26 users show that the overall concept is easily understandable and that it seems useful to end‐users. An analysis of real‐world and simulated location traces shows that user privacy can be ensured, but with a trade‐off between privacy protection and consumed network resources.

Air‐Writing, both as an architectural concept and as a specific implementation, are immediately applicable to practical, globally scalable, private group messaging systems. A publicly available messaging platform is already online as beta version at http://airwriting.com Originality/value – Air‐Writing addresses three concerns: flexibility concerning arbitrary messaging applications, user privacy, and global scalability of the associated web service. To the best of the authors' knowledge, previous approaches focus on at most two of these issues, while the authors' approach allows all three requirements to be fulfilled.

Personal mobile devices currently have access to a significant portion of their user's private sensitive data and are increasingly used for processing mobile payments. Consequently, securing access to these mobile devices is a requirement for securing access to the sensitive data and potentially costly services. The authors propose and evaluate a first version of a pan shot face unlock method: a mobile device unlock mechanism using all information available from a 180° pan shot of the device around the user's head – utilizing biometric face information as well as sensor data of built‐in sensors of the device. The paper aims to discuss these issues.

This approach uses grayscale 2D images, on which the authors perform frontal and profile face detection. For face recognition, the authors evaluate different support vector machines and neural networks. To reproducibly evaluate this pan shot face unlock toolchain, the authors assembled the 2013 Hagenberg stereo vision pan shot face database, which the authors describe in detail in this article.

Current results indicate that the approach to face recognition is sufficient for further usage in this research. However, face detection is still error prone for the mobile use case, which consequently decreases the face recognition performance as well.

The contributions of this paper include: introducing pan shot face unlock as an approach to increase security and usability during mobile device authentication; introducing the 2013 Hagenberg stereo vision pan shot face database; evaluating this current pan shot face unlock toolchain using the newly created face database.

The purpose of this paper is to design, implement and evaluate the usage of the password-authenticated secure channel protocol SRP to protect the communication of a mobile application to a Java Card applet. The usage of security and privacy sensitive systems on mobile devices, such as mobile banking, mobile credit cards, mobile ticketing or mobile digital identities has continuously risen in recent years. This development makes the protection of personal and security sensitive data on mobile devices more important than ever.

A common approach for the protection of sensitive data is to use additional hardware such as smart cards or secure elements. The communication between such dedicated hardware and back-end management systems uses strong cryptography. However, the data transfer between applications on the mobile device and so-called applets on the dedicated hardware is often either unencrypted (and interceptable by malicious software) or encrypted with static keys stored in applications.

To address this issue, this paper presents a solution for fine-grained secure application-to-applet communication based on Secure Remote Password (SRP-6a and SRP-5), an authenticated key agreement protocol, with a user-provided password at run-time.

By exploiting the Java Card cryptographic application programming interfaces (APIs) and minor adaptations to the protocol, which do not affect the security, the authors were able to implement this scheme on Java Cards with reasonable computation time.

The purpose of this paper is to address the design, implementation, performance and limitations of an environment that emulates a secure element for rapid prototyping and debugging. Today, it is difficult for developers to get access to a near field communication (NFC)-secure element in current smartphones. Moreover, the security constraints of smartcards make in-circuit emulation and debugging of applications impractical. Therefore, an environment that emulates a secure element brings significant advantages for developers.

The authors' approach to such an environment is the emulation of Java Card applets on top of non-Java Card virtual machines (e.g. Android Dalvik VM), as this would facilitate the use of existing debugging tools. As the operation principle of the Java Card VM is based on persistent memory technology, the VM and applications running on top of it have a significantly different life cycle compared to other Java VMs. The authors evaluate these differences and their impact on Java VM-based Java Card emulation. They compare possible strategies to overcome the problems caused by these differences, propose a possible solution and create a prototypical implementation to verify the practical feasibility of such an emulation environment.

While the authors found that the Java Card inbuilt persistent memory management is not available on other Java VMs, they present a strategy to model this persistence mechanism on other VMs to build a complete Java Card run-time environment on top of a non-Java Card VM. Their analysis of the performance degradation in a prototypical implementation caused by additional effort put into maintaining persistent application state revealed that the implementation of such an emulation environment is practically feasible.

This paper addresses the problem of emulating a complete Java Card run-time environment on top of non-Java Card virtual machines which could open and significantly ease the development of NFC secure element applications.

The purpose of this paper is to review the state-of-the-art in adaptive user interface systems by studying their historical development over the past 20 years. Moreover, this paper contributes with a specific model combining three main entities (users, context and devices) that have been demonstrated to be always represented in these environments. Novel concepts that should be taken into account in these systems are also presented.

The authors first provide a review and a comparison of current user interface adaptive systems. Next, the authors detail the most significant models and the set of techniques used to, finally, propose a novel model based on the studied literature.

Literature solutions for adaptive user interface systems tend to be very domain dependant. This situation restricts the possibility of sharing and exporting the information between such systems. Furthermore, the studied approaches barely highlight the dynamism of these models.

The paper is a review of adaptive user interface systems and models. Although there are several reviews in this area, there is a lack of research for modelling users, context and devices simultaneously in this domain. The paper also presents several significant concepts that should be taken into account to bring an adaptive and dynamic perspective to the studied models.

Scalability is a fundamental problem in mobile ad hoc networks (MANETs), where network topology includes large number of nodes and demands a large number of packets in network that characterized by dynamic topologies, existence of bandwidth constrained, variable capacity links, energy constraint and nodes are highly prone to security threats. The key purpose of this paper is to overview the efficiency of the proposed clustering scheme for large-scale MANETs and its performance evaluation and especially in the case of a large number of nodes in the network.

Designing clustering schemes for MANETs, which are efficient and scalable in the case of large number of mobile nodes, has received a great attention in the last few years. It is widely used to improve resources management, hierarchical routing protocol design, quality of service, network performance parameters such as routing delay, bandwidth consumption, throughput and security. MANETs are characterized by limited wireless bandwidth, nodes mobility that results in a high frequency of failure regarding wireless links, energy constraint and nodes are highly prone to security threats. Due to all these features, the design of a scalable and efficient clustering scheme is quite complex. Many clustering schemes have been proposed to divide nodes into clusters, focusing on different metrics and purposes.

To the best of the author's knowledge, the different proposed clustering schemes are not scalable when the network size increases to a very large number. The paper presents the clustering scheme in detail and its performance evaluation by simulating MANETs composed of a large number of mobile nodes. The authors compare the performance of the scheme with a number of existing clustering schemes such as lowest-ID, highest degree, and weighted clustering algorithm, based on a number of performance metrics. Simulation results show that the scheme performs better than other clustering schemes, based on the performance metrics considered, for large-scale MANETs.

This paper addresses the problem of scalability in MANETs when there are high numbers of node in the network. The paper analyses the performance of the proposed clustering scheme for large-scale MANETs. The obtained results show that the different proposed clustering schemes do not allow the scalability when the network size is very large. The scheme supports scalability efficiently when the number of nodes increases in the network (more than 2,000 nodes).

The authors present a low-cost unmanned aerial vehicle (UAV) for autonomous flight and navigation in GPS-denied environments using an off-the-shelf smartphone as its core on-board processing unit. Thereby, the approach is independent from additional ground hardware and the UAV core unit can be easily replaced with more powerful hardware that simplifies setup updates as well as maintenance. The paper aims to discuss these issues.

The UAV is able to map, locate and navigate in an unknown indoor environment fusing vision-based tracking with inertial and attitude measurements. The authors choose an algorithmic approach for mapping and localization that does not require GPS coverage of the target area; therefore autonomous indoor navigation is made possible.

The authors demonstrate the UAVs capabilities of mapping, localization and navigation in an unknown 2D marker environment. The promising results enable future research on 3D self-localization and dense mapping using mobile hardware as the only on-board processing unit.

The proposed autonomous flight processing pipeline robustly tracks and maps planar markers that need to be distributed throughout the tracking volume.

Due to the cost-effective platform and the flexibility of the software architecture, the approach can play an important role in areas with poor infrastructure (e.g. developing countries) to autonomously perform tasks for search and rescue, inspection and measurements.

The authors provide a low-cost off-the-shelf flight platform that only requires a commercially available mobile device as core processing unit for autonomous flight in GPS-denied areas.

Coexistence of various wireless access networks and the ability of mobile terminals to switch between them make an optimal selection of serving networks for multicast groups a challenging problem. Since optimal network selection requires large dimensions of data to be collected from several network locations and sent between several network components, the scalability can easily become a bottleneck in large-scale systems. Therefore, reducing data exchange within heterogeneous wireless networks is important. The paper aims to discuss these issues.

The authors study the decision-making process and the data that need to be sent between different network components. To analyze the operation of the wireless heterogeneous network, the authors built a mathematical model of the network. The objective is defined as a minimization of multicast streams in the system. To evaluate the heuristic solutions, the authors define the upper and lower bounds to their operation.

The proposed heuristic solutions substantially reduce the usage of bandwidth in mobile networks and exchange of information between the network components.

The authors proposed the approach that allows network selection in a decentralized manner with only limited information shared among the decision makers. The authors studied how different sets of information available to decision makers influenced the performance of the system. The work also investigates the usage of multiple paths for multicast in heterogeneous mobile environments.