http://theses.ncl.ac.uk/jspui/handle/10443/87 2026-02-04T10:50:55Z http://theses.ncl.ac.uk/jspui/handle/10443/6023 Title: Post quantum cryptography : alternative solutions to hard problems for security Authors: Emerole, Kelechi Chukwunonyerem Abstract: Post Quantum cryptography are defined as public key crypto algorithms whose pub lic keys are generated from hard computational problems that are complex to solve in polynomial time by a quantum computer given worst case instances. The hard problems which have been proven to be quantum resistant include the shortest vec tor problem of lattices, the syndrome decoding problem of certain error correcting codes and the isomorphism of polynomial problem of multivariate quadratic poly nomials. Solutions to these problems have been proposed which in turn have impact on the security and storage cost of such algorithms to protect information systems in the future. In this thesis, alternative solutions are proposed which are based on robust and complex vector space mappings. Firstly, Dimensionality mapping is pro posed to reduce the basis into its linear independent vectors at low dimensionality by constructing a collapse function as an optimization problem. This optimization problem can be solved on the condition that a projection of the basis vectors from the High dimensional space to low dimensional manifold would have nearly orthogonal constitution. These eliminates the need for pre-processing using Gram-Schmidt Or thogonalization process. Implementing this approach on a channel basis, showed an improved BER performance over the Lenstra-Lenstra-Lovatsz algorithm for about 1db and 4db in the 4 × 4 and 6 × 6 uncoded system using 4QAM constellation. Secondly, the solution of the syndrome decoding problem is generalized to codes associated with the totally non-negative Grassmannian. The solution was reduced to an instance of finding a subset of the Pl¨ucker coordinates with the minimum Grassmann distance from the subspace containing the encrypted message symbols. Furthermore, bounds where derived which showed that the complexity scales up on the size of the Pl¨ucker coordinates. In addition, experimental results on decoding failure probability and complexity based on row operations where presented and compared to Low Density parity check codes in the Hamming metric. Finally, the kernel function of the New Mersenne number transform was applied to hide the 4 structure of the core map(central polynomial) of a multivariate polynomial based cryptosystem. This is in order to mitigate the interpolation of the rank of the quadratic form by an adversary. The implementation of this new isomorphism from the New Mersenne Number Transform showed an average of 69% reduction in secret key size. Further implementation of the isomorphism against key recovery attacks from the MinRank instance where carried out and it was shown that for lower field sizes the new isomorphism had an average success time of 13.8%. Description: PhD Thesis 2023-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/3606 Title: Integration of Biometrics and PIN Pad on Smart Card Authors: Yang, Chunlei Abstract: Secure payment is the basis of electronic commerce (e-commerce). A large amount of electronic payments are made via POS (point of sale) terminals using smart cards and legitimate users are usually authenticated by PIN. The security design of POS terminals and authentication methods are increasingly becoming concerns of ebusiness. The major aims and objectives of this industrially oriented research are to investigate a new solution at system level to improve the security of current POS payment systems. The contributions of this thesis include several aspects: 1) An indepth literature survey has been undertaken. The security threats of current POS terminals and available countermeasures have been systematically investigated. The main existing problems have been identified. 2) An innovative scheme, the so-called Supercard, which integrates PIN pad, biometrics and the smartcard, has been proposed. Approaches based on this scheme can meet security challenges posed by attacks such as visual and channel PIN attacks, display attacks, and fake-machine attacks. The scheme also has advantages to prevent the cryptographic key being disclosed by channel or side channel attacks. 3) The Supercard scheme has been examined specifically to improve fingerprint biometrics security. The Capture & Match on Card scheme and corresponding authentication protocol has been designed with the advantage of preventing biometric channel attacks. Biohash is adopted to protect the biometric template. 4) Keystroke dynamics, as a behaviour biometric to strengthen PIN authentication, has been investigated under the specific conditions of a highly limited number of keystrokes. 5) The multimodal signals of PIN, fingerprint and keystroke dynamics have been studied through fuzzy-logic-based information fusion. Description: PhD Thesis 2011-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/3587 Title: Assessment of single phase SRM converters for low power applications Authors: Ayob, Afida Abstract: The switched reluctance machine (SRM) is the least expensive machine to produce yet is very reliable. The drive system for an SRM has to be designed so that there is integration between the machine and the converter-controller configuration. This thesis represents a study relating to power electronic converters for single-phase switched reluctance machine drives with emphasis on the cost of implication of the converters. The study of the converters results in the proposal of a new converter concept based on minimising the cost contribution of the dc link capacitor. By reducing the size of the capacitor, smaller and lighter SP-SRM drive is achieved. A detailed analysis and simulation of the proposed converter has been conducted and enabled a design guideline for the proposed converter to be laid out. A model of the SRM with hysteresis controller is developed. Consequently, components have to be chosen carefully to minimise voltage dip, component stress, and energy loss from the freewheeling resistor. To verify the operation of the new converter, tests were conducted on an experimental rig. The proposed converter has the ability to supply double the peak supply of voltage to the machine winding. In addition, the arrangement of the capacitors and diodes in the voltage multiplier means that positive and negative voltage rails can be supplied to the machine, which is very useful in an SP-SRM drive. The high voltage allows the fast magnetisation of the windings and enables the machine to achieve potentially high speed. Through the arrangements of the capacitors and diodes, the converter is able to handle recovered energy form the windings. Description: PhD Thesis 2011-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/3487 Title: Biometric iris image segmentation and feature extraction for iris recognition Authors: Ukpai, Charles Onyebuchi Abstract: The continued threat to security in our interconnected world today begs for urgent solution. Iris biometric like many other biometric systems provides an alternative solution to this lingering problem. Although, iris recognition have been extensively studied, it is nevertheless, not a fully solved problem which is the factor inhibiting its implementation in real world situations today. There exists three main problems facing the existing iris recognition systems: 1) lack of robustness of the algorithm to handle non-ideal iris images, 2) slow speed of the algorithm and 3) the applicability to the existing systems in real world situation. In this thesis, six novel approaches were derived and implemented to address these current limitation of existing iris recognition systems. A novel fast and accurate segmentation approach based on the combination of graph-cut optimization and active contour model is proposed to define the irregular boundaries of the iris in a hierarchical 2-level approach. In the first hierarchy, the approximate boundary of the pupil/iris is estimated using a method based on Hough’s transform for the pupil and adapted starburst algorithm for the iris. Subsequently, in the second hierarchy, the final irregular boundary of the pupil/iris is refined and segmented using graph-cut based active contour (GCBAC) model proposed in this work. The segmentation is performed in two levels, whereby the pupil is segmented first before the iris. In order to detect and eliminate noise and reflection artefacts which might introduce errors to the algorithm, a preprocessing technique based on adaptive weighted edge detection and high-pass filtering is used to detect reflections on the high intensity areas of the image while exemplar based image inpainting is used to eliminate the reflections. After the segmentation of the iris boundaries, a post-processing operation based on combination of block classification method and statistical prediction approach is used to detect any super-imposed occluding eyelashes/eyeshadows. The normalization of the iris image is achieved though the rubber sheet model. In the second stage, an approach based on construction of complex wavelet filters and rotation of the filters to the direction of the principal texture direction is used for the extraction of important iris information while a modified particle swam optimization (PSO) is used to select the most prominent iris features for iris encoding. Classification of the iriscode is performed using adaptive support vector machines (ASVM). Experimental results demonstrate that the proposed approach achieves accuracy of 98.99% and is computationally about 2 times faster than the best existing approach. Description: PhD Thesis 2016-01-01T00:00:00Z