A Secure and Efficient Key Exchange Protocol for Mobile Communications

This paper proposes a key exchange protocol with mutual authentication, which requires only 0.1 modular multiplications for online computations. This online computation is ten times faster than that of conventional protocols. The message size of the proposed protocol is about half (50%~66%) that of the previous protocols. In addition to its efficiency in online computation and bandwidth, the paper provides a formal proof to guarantee the security of the proposed protocol. Possessing of both secure and efficient properties makes the proposed protocol suitable for the low power mobile communications

Authentication under Constraints

Authentication has become a critical step to gain access to services such as on-line banking, e-commerce, transport systems and cars (contact-less keys). In several cases, however, the authentication process has to be performed under challenging conditions. This thesis is essentially a compendium of five papers which are the result of a two-year study on authentication in constrained settings. The two major constraints considered in this work are: (1) the noise and (2) the computational power. For what concerns authentication under noisy conditions, Paper A and Paper B ad- dress the case in which the noise is in the authentication credentials. More precisely, the aforementioned papers present attacks against biometric authentication systems, that exploit the inherent variant nature of biometric traits to gain information that should not be leaked by the system. Paper C and Paper D study proximity- based authentication, i.e., distance-bounding protocols. In this case, both of the constraints are present: the possible presence of noise in the channel (which affects communication and thus the authentication process), as well as resource constraints on the computational power and the storage space of the authenticating party (called the prover, e.g., an RFID tag). Finally, Paper E investigates how to achieve reliable verification of the authenticity of a digital signature, when the verifying party has limited computational power, and thus offloads part of the computations to an untrusted server. Throughout the presented research work, a special emphasis is given to privacy concerns risen by the constrained conditions

Efficient key management protocols for mobile ad hoc networks

In this thesis, novel solutions are proposed for key management issues in mobile ad hoc networks. Presented Hierarchical Binary Tree (HBT) based model is distributed, self-organizing, scalable and does not employ online key distribution authority or group manager. Two different group authentication and group key establishment protocols are proposed for the users who form an ad hoc group with distributed trust model. Initially proposed protocols are based on public key cryptography and do not use specific algorithm. However, members can establish the keys faster with proposed customized hybrid scheme which combines elliptic curve cryptography, modular squaring operations and secret key encryption algorithm. Proposed HBT based model provides complete backward and forward security in case of modification in membership and it has comparable efficiency to the other HBT based schemes which employ real time key distribution authority. Mutual authentication and link encryption can be achieved in wireless sensor network only with public key cryptography if there are no pre-distributed keys. However, constraints in resources make fully public key operations not affordable on sensor. Three different authenticated key establishment protocols are proposed with an objective of being respectful to constraints. Sensor needs to make only modular or cyclic convolution multiplications, and expensive public key decryption operation is executed at the data processing station side. Schemes require small size of code and achieve the least sensor processing time in comparison with fully public key cryptography based protocols

Learning Optimal Resource Allocations In Wireless Systems

The goal of this thesis is to develop a learning framework for solving resource allocation problems in wireless systems. Resource allocation problems are as widespread as they are challenging to solve, in part due to the limitations in finding accurate models for these complex systems. While both exact and heuristic approaches have been developed for select problems of interest, as these systems grow in complexity to support applications in Internet of Things and autonomous behavior, it becomes necessary to have a more generic solution framework. The use of statistical machine learning is a natural choice not only in its ability to develop solutions without reliance on models, but also due to the fact that a resource allocation problem takes the form of a statistical regression problem. The second and third chapters of this thesis begin by presenting initial applications of machine learning ideas to solve problems in wireless control systems. Wireless control systems are a particular class of resource allocation problems that are a fundamental element of IoT applications. In Chapter 2, we consider the setting of controlling plants over non-stationary wireless channels. We draw a connection between the resource allocation problem and empirical risk minimization to develop convex optimization algorithms that can adapt to non-stationarities in the wireless channel. In Chapter 3, we consider the setting of controlling plants over a latency-constrained wireless channel. For this application, we utilize ideas of control-awareness in wireless scheduling to derive an assignment problem to determine optimal, latency-aware schedules. The core framework of the thesis is then presented in the fourth and fifth chapters. In Chapter 4, we formally draw a connection between a generic class of wireless resource allocation problems and constrained statistical learning, or regression. From here, this inspires the use of machine learning models to parameterize the resource allocation problem. To train the parameters of the learning model, we first establish a bounded duality gap result of the constrained optimization problem, and subsequently present a primal-dual learning algorithm. While any learning parameterization can be used, in this thesis we focus our attention on deep neural networks (DNNs). While fully connected networks can be represent many functions, they are impractical to train for large scale systems. In Chapter 5, we tackle the parallel problem in our wireless framework of developing particular learning parameterizations, or deep learning architectures, that are well suited for representing wireless resource allocation policies. Due to the graph structure inherent in wireless networks, we propose the use of graph convolutional neural networks to parameterize the resource allocation policies. Before concluding remarks and future work, in Chapter 6 we present initial results on applying the learning framework of the previous two chapters in the setting of scheduling transmissions for low-latency wireless control systems. We formulate a control-aware scheduling problem that takes the form of the constrained learning problem and apply the primal-dual learning algorithm to train the graph neural network

Novel and Compact Reconfigurable Antennas for Future Wireless Applications

PhDThe development of reconfigurable antennas is considered to be very promising in modern and future communication systems. Reconfigurable antennas have made use of many reconfiguration techniques that are centred upon switching mechanisms such as p-i-n diodes or MEMS. Other techniques such as optical switches, mechanical structure changing or the ability to change the permeability or permittivity of smart substrate materials have also been used. Reconfigurable antennas have created new horizons for many types of applications especially in Cognitive Radio, Multiple Input Multiple Output Systems, personal communication systems, satellites and many other applications. Cognitive Radio is one of the potential wireless applications that may place severe demands on RF systems designers and particularly antenna designers, when it comes to providing exible radio front-ends capable of achieving the set objectives of the technology. The aim of this work is to investigate possible roles that different categories of reconfigurable antenna can play in cognitive and smart radio. Hence, the research described in this thesis focuses on investigating some novel methods to frequency-reconfigure compact ultra-wideband antennas to work in different bands; this will offer additional filtering to the radio front-end. In the ultra-wideband mode, the antenna senses the spectrum for available bands with less congestion and interference and hence decides on the most suitable part to be reconfigured to, allowing reliable and efficient communication links between the radio devices. Ultra-wideband antenna with reconfigurable integrated notch capability is also demonstrated to provide further enhancement to interference rejection and improve the overall communication link. Furthermore, the design of novel pattern and polarisation reconfigurable antennas will be also investigated to assist Cognitive Radio through spatial rather than frequency means. An ultimate target for this research is to combine different degrees of reconfiguration into one compact, state of the art antenna design that meets the growing demand of cognitive and smart radio devices for more intelligent and multi-functional wireless devices within the personal area network domains and beyond

Keeping Fairness Alive : Design and formal verification of optimistic fair exchange protocols

Fokkink, W.J. [Promotor]Pol, J.C. van de [Promotor

Secondary technical schools in England and Wales : A study of administrative and curriculum policies

The impact of vocationalism on secondary education in England and Wales has been limited in range and incidence. This study examines some of the attempts to give expression to practical education in schools between 1889 and 1965. It focuses on institutions specifically charged with providing a technical education to pupils of secondary school age, with particular reference to Junior and Secondary Technical Schools. Collectively, the technical schools were casualties of policies which emphasized their instrumental nature, and which failed to secure their ambiguous institutional foundations. This impeded the projection of the educational benefits of vocationalism. Nor were curriculum policies clear about the favoured methods, content or disposition of secondary technical education. Practical education denoted an ambition rather than an agreed approach to secondary education. Administrative and curriculum policies lacked the coherence necessary if new ideas were to be presented successfully. These contentions are elucidated through an examination of central and local policies. These were determined by the interaction between administrative, professional, industrial and political interests. Reference is also made to some of the contemporary justifications of practical education. Enabling policies originated in the localities and found expression in a number of institutions. They were belatedly endorsed by the central department. In the process an 'ideal' type emerged, the 'Technical High School of Science'. It was intended to be the vocational counterpart of the academic grammar school. With its emphasis on scientific and technological concerns it represented one strand of practical education. Changes in science, technology and employment have meant that the curriculum of the technical schools no longer reflects contemporary needs. Their concern with practical education, however, remains undiminished. Their importance lies in the assistance they provide in posing questions about present day practices. The history of the technical schools underlines the need to define precisely the meaning of vocationalism. In the period under discussion, 'vocationalism' was the starting point for disagreements about the nature and purposes of practical education. 'Liberal' vs. 'Vocational'; 'Education' vs. 'Training' were standard formulations which left little room for synthesis. The case for vocationalism was un-coordinated . It was hindered by a disinclination to include curriculum issues alongside matters of provision. It was left to individuals, sectional groups, and sympathetic administrators who approached the subject from a multiplicity of viewpoints and institutional settings