| Summary: | 博士 === 國立中正大學 === 資訊工程所 === 96 === Wired and wireless networks have become one of the most important communication mediums in daily lives since 1980s. Specifically, with the support of the Government and rapid growth of the industry, network technologies are developed with giant strides recently. Through network communications, people can connect with each other without direct contact. Thus, how to prevent communications from being eavesdropped, fabricated, and intruded becomes the main challenge of a network system design. In this study, we focus on the following subjects: (1) Authentication for wireless networks, (2) Secure communications for ad hoc networks, (3) Electronic commerce, and (4) Oblivious transfer protocol. For the first subject, we propose brand-new authentication protocols to solve the drawbacks of GSM, including storage overheads, bandwidth consumption, and single authentication. Furthermore, we present an efficient method for validating the legitimacy of user in mobile networks. Specifically, the new method preserves the property of anonymity so that the intruder can not track the movement history of mobile subscribers. For the subject of ad hoc networks, they are self-configurable and autonomous systems consisting of routers and hosts, which are able to move and organize themselves arbitrarily. This means that the topology of the ad hoc network changes dynamically and unpredictably. Without fixed infrastructure, it is difficult for people to distinguish an insider or outsider of a wireless network. We therefore propose an effective method to provide secure communications in such network environment. As regards the subject of electronic commerce, we design a secure method for mobile transactions and two e-voting mechanisms. E-voting has become a popular research topic due to its mobility and convenience. Unfortunately, existing methods can not completely meet the critical requirements of general e-voting mechanisms. Employing the blind signature and Diffie-Hellman key exchange protocol, the proposed methods can not only achieve all the essentials but also possess better performance than related works. Mentioning oblivious transfer protocol, it is an important cryptography tool in recent decades, which can be used in many emerging applications such as e-commerce, secret exchange, coin flipping by telephone or the certificated e-mail sending. In this dissertation, we have proposed a t-out-of-n version which is provable secure and more efficient than related works.
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