Studies In Secure Computation And Application

The problem of secure multiparty computation is fundamental in cryptography, as well as relevant to practical cryptographic applications. In particular, almost any known cryptographic set and problems can be viewed as a special case of this general problem, e.g., encryption, authentication, commitment, signatures, zero- knowledge, and many others. Thus, secure computation may serve as a general, uniform paradigm for the study of most of cryptography. Furthermore, understanding secure multiparty computation is fundamental in the study of distributed system in general. This paper discusses this problem in such aspects, especially in applied it into solving signing contracts and security of network system.The oblivious transfer protocol (OT) is an important foundation of cryptography and has become the basis for realizing interactive protocols, especially in the field of the secure multiparty computation. It has been studied in various flavors and security models extensively, but most OT protocols are based on intractability of factoring. This paper introduces a new oblivious protocol based on intractability of the elliptic curve discrete logarithm problem (ECDLP). Because ECDLP doesn't exist the subexponential-time algorithm, we can obtain the same security by the much shorter key length and improve the processing time and communication costs. Furthermore, we prove that this protocol is security against the malicious attacker.Since simultaneous exchange signature is usually impossible in practice, protocols are needed to approximate simultaneity by exchange partial commitments in piece-by-piece manner. The party of secondly sending commitments may have a slight advantage; a"fair"protocol must keep this advantage within acceptable limits. We improve the protocol for signing contract based on the research result of secure multiparty computation. In this protocol, the parties obliviously transfer the signed bit and the committed bit; the other parties can prove the validity of this bit based on the confirming sub-protocol, but he can't gain more information about the whole signature by accumulating the more signed bit or the committed bit. After the parties exchange the whole signed information, they declare the commitment about the signature respectively, and gain the whole signature of the other party. At this moment, the party doesn't care about the advance quit of the other party, because he has gained the whole signed information. Finally, we prove that this protocol is quit-fairness.We introduced the multiparty secure computation. In the environment, we discussed the VSS protocol and Commodity Server model. In the paper, we designed a new...