Research On Digital Signatures With Additional Properties And Fair Exchange Protocols

Information security is one of the most important problems in modern information society.Digital signature, which can prove authentication, integrity and non-repudiation, is one of the key techniques of information security and plays a very important role in E-commerce and E-governance. As the deepening of digital signature research, the standard signature, which is a simple simulacrum of handwritten signature, can not still meet the need in practice, thus making research on the digital signatures with additional properties becomes a main research direction in digital signature. An important issue of e-commerce based on information technology is how to exchange electronic data between two potentially distrusted parties in an efficient and fair manner. Fair exchange protocol can allow two distrusted parties to exchange their items in a fair way, thereby has become an important security mechanism. The research of this thesis consists of the following two parts: design and analysis of digital signatures with additional properties, design and analysis of fair exchange protocols.The mainly obtained results are as follows:1. ID-based digital signature schemes proposed in recent years are reviewed, and the direction and future works of this research field are summarized.2. One forgery attack is proposed on a proxy blind signature scheme proposed by Wang et al. By successfully identifying the forgery attack, we show that their scheme is insecure and has a design flaw. Furthermore, to improve Wang et al's scheme, we propose a new proxy blind signature scheme.3 A secure ID-based proxy blind signature scheme is proposed by using the knowledge of ID-based cryptography, and the security properties and its applications are discussed later. 4 Comparing fair exchange protocol with traditional security protocol, we summarize and refine three important principles of designing fair exchange protocol.5 A new fair exchange protocol with semi-trusted third party is proposed based on a new convertible authenticated encryption scheme, and both security properties and specialties of this protocol are analyzed.6 A fair and optimistic contract signing protocol, which is based on a standard signature scheme and a verifiable and recoverable encrypted signature (VRES) from bilinear pairings, is proposed, and the security properties of this scheme is analyzed detailedly.7 We summarize almost all the security properties which must be considered in designing a certified email protocol, and then we give two optimistic certified email protocols , which are based on the offline TTPs.