In an anonymous credential system, when a credential has been shown for verification, none can identify the owner of the credential and link the relationship between any two credentials. The unlinkability is the crucial feature for any anonymous credential system. In 2002, Jan Camenisch and Anna Lysyanskaya proposed a signature scheme (CL signature) which allows users to demonstrate their credentials without revealing their identity information. However, CL signature is compounded of a lot of zero-knowledge proof technologies which cause inefficiency for CL signatures. Such heavy computation requirements may limit the scope which CL signatures can be applied to. In this thesis, we propose a new blind signature scheme based on ElGamal signatures and design an anonymous verification procedure which is more efficient than the CL signature scheme. Finally, we also implement our proposed protocols.

Digital signature is widely used to implement many secure protocols. A digital signature has three parameters. They are the message, the key pair, and the signature. In general, the message is given. The key pair is chosen randomly by the signer. The signature is computed from the message and the key pair. But in some cases, we can choose the value of one of the parameters, this may make it possible to other applications such as blind signatures or subliminal channels. There are some researches to discuss the relations between the parameters and the applications of the digital signatures. In this research, we will propose three new schemes as examples of this technique. The first one is a fair blind signature scheme. The other two are subliminal channel schemes. These three new schemes have some important properties. The concept of this research may help the future researches to find new applications of the digital signature. Meanwhile, these new schemes can show that how the concept can help us to develop or improve applications.

Identification schemes are public-key cryptographic primitives that allow an entity (called the prover) to prove his or her identity to another entity. An identification scheme is secure if no attacker can impersonate the prover. Digital signature schemes allow an entity to produce a signature on a message; given the message and the signature, another entity can check the identity of the signer and verify that the message was not modified. A secure digital signature scheme is such that an attacker can not produce a forgery, i.e. a false signature. There has been a lot of work aiming at establishing, in a provable manner, the security of such schemes. Given a cryptographic scheme and a security property, one should be able to demonstrate whether the scheme satisfies it or not. The approach is usually the following: when the security property is not satisfied, show it with an efficient attack; when it is satisfied, use a security proof. But even when they are provably secure, cryptographic schemes can be attacked: it can be at the implementation level, or because of a flaw in the proof. The goal of this thesis is to apply these approaches to study the security of several public-key cryptographic schemes. We study the GPS identification scheme and show how some implementations can be broken by an efficient attack. We show how to securely sign long messages with RSA. We break a fair exchange signature scheme based on GPS and RSA. We consider a new problem called fair identification and propose a fair identification scheme.

Grinding operations can be analyzed through monitoring and analysis of the spindle power during the process. Due to the complexity of the process, the analysis on grinding processing signal still heavily relies on personal experience of the engineer instead of having a standard structured method. Therefore, subjectivity and inconsistency is introduced into the analysis procedure. In this thesis, a general method is established to characterize signal, utilize the characterization result to predict the real time condition of grinding wheels and the impact on the process performance measures, and provide suggestions in modification of process parameters to improve the grinding operation. This method is initiated from signal acquisition and conducted based on characterizing the signal and organizing expert knowledge. When the standard procedure to analyze the grinding process through power signal is established, the correlation between input and output can be understood, which can later be utilized for diagnostic applications. During the diagnosis, the real-time grinding wheel status is estimated and the output of the process is predicted. Then, suggestions on modifying the input parameters to address given output issue are generated. Therefore, a signal analysis and knowledge based monitoring and diagnosing system is developed to help enhance the current grinding process planning. This system is realized with a software tool developed with specifically designed algorithms under Matlab environment, upgrading from manual signal processing to an automated characterization procedure and providing process evaluation and improvement suggestions, which will improve the objectivity, consistency and accuracy in the analysis of grinding processes.

M.Tech. / There is evidence of a growing concern regarding the authenticity of qualifications presented at interviews. Today's computer software makes it simple to edit documents, thereby allowing falsification of information by the unscrupulous. The use of sophisticated document scanners, printers and copiers further complicates the issue. The research revolved around an investigation of the need for authentication of education qualifications and the establishment of the feasibility of doing this by using information technology and the World Wide Web to allow for efficient and effective verification that an education qualification was attained at the named higher education institution and that the results were accurately reflected. The research method included the use of questionnaires to gather data. Questionnaires were sent to the registrars of universities and technikons and Human Resources directors of Gauteng-based employer companies. Responses to the questionnaires and information gleaned from the literature review were used in the models designed and offered as solutions to the problem of qualification fraud. The main conclusions drawn from the research were: Confirmation of the growing incidence of and concern regarding qualification fraud. Establishment of the need for a solution to allow authentication of qualifications by Human Resource practitioners as part of the recruitment process. The feasibility for this solution to be an information technology solution using World Wide Web. The VeriQual model was designed to meet all the research objectives. This innovative model is deemed to offer an efficient, effective and feasible technology solution to the problem of qualification fraud in South Africa.

In today’s society signatures are the most accepted form of identity verification. However, they have the unfortunate side-effect of being easily abused by those who would feign the identification or intent of an individual. This thesis implements and tests current approaches to off-line signature verification with the goal of determining the most beneficial techniques that are available. This investigation will also introduce novel techniques that are shown to significantly boost the achieved classification accuracy for both person-dependent (one-class training) and person-independent (two-class training) signature verification learning strategies. The findings presented in this thesis show that many common techniques do not always give any significant advantage and in some cases they actually detract from the classification accuracy. Using the techniques that are proven to be most beneficial, an effective approach to signature verification is constructed, which achieves approximately 90% and 91% on the standard CEDAR and GPDS signature datasets respectively. These results are significantly better than the majority of results that have been previously published. Additionally, this approach is shown to remain relatively stable when a minimal number of training signatures are used, representing feasibility for real-world situations.

Using computational deterministic and Monte Carlo methods, I present an analysis of the gamma and neutron signatures emitted from special nuclear material (SNM) in weapons stockpile storage scenarios. My efforts are focused on 1 year old, 25 year old, 50 year old, and 75 year old highly enriched uranium (HEU), and 1 year old, 22.5 year old, and 50 year old weapons grade plutonium (WGPu). HEU gammas are easily shielded, and when reasonably shielded, do not produce a definable signature at low energies; however, using new methods applied in this work that involve analyzing the higher energy, penetrating gammas from HEU, it can be shown that not only the presence of the HEU can be verified, but also the age since separation of the material can be discerned. Through computational modeling, I am able to verify that the novel methods investigated are both unique and effective for HEU detection. In addition, I also present my investigation of similar methods applied to the detection of WGPu. From this work I determined that WGPu age discrimination is more challenging compared to that of HEU (in spite of more radiation per unit mass) due to the high rate of induced gammas from n-gamma interactions taking place within the Pu metal and container; however, I believe that by combining neutron detection with gamma signature verification of WGPu, the approach identified can be successful. I present the neutron signature of the WGPu and how it would be observed in the detector used for material verification. I calculated the detector response for a pre-determined neutron detector design using adjoint calculations in order to determine whether the detector will perform as designed. In addition to developing a new protocol for WGPu detection, I present in this work, a comprehensive source book as a product of this research, detailing the gamma and neutron signatures for both solid and shell configurations of HEU and WGPu. This can serve as a very beneficial guide for anyone interested in modeling SNM, since the many steps needed to obtain this radiation leakage data will save a significant amount of researcher time. The results from my work have contributed to a collaborative effort supporting funded US department of State research towards designing a mobile detection system that can rapidly validate and verify the presence of SNM in weapons pit containers.

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