Improving security and efficiency of electronic cash and mobile agent applicable to electronic commerce

Abstract

As the network technologies including Internet technology have been developed tremendously, the electronic commerce becomes prosperous and easier to be implemented in the real world. The electronic commerce requires various services such as electronic payment, electronic mail, agent system, etc. Here, security is critical and there have been many researches for security issues. As part of the researches, we propose, in this thesis, efficient revocable electronic cash protocol and secret computation with secrets for the mobile agent. We have designed an efficient revocable electronic cash system whose main security is based on ECDLP ( Elliptic Curve Discrete Logarithm Problem). To achieve this, we have employed a known secure electronic cash system based on DLP(Discerete Logarithm Problem) suggested by Petersen and Poupard [PePo97] and extended it on an elliptic curve over the finite field. This naturally reduces the message to 85% compared with the original scheme and makes it possible to handle a smart card. Furthermore, we have achieved more secure and efficient electronic cash system by using Sing and Kim``s key agreement protocol [BKOO] and Baek et al.``s provably secure public key encryption scheme [BLKOO]. Strengthening the security of mobile agent is emphasized for the following research. The mobile agent is now used to search for special products or services and is executed for a specific job designated by a customer in the server``s environment on behalf of a customer. On the way of performing its role, a mobile agent can be vulnerable to several cryptographic attacks. These attacks can be more serious when done by malicious servers. Among schemes to deal with these problems, the concept of encrypted function for secret computation proposed in [ST97, KBCOO] is one server (host) to execute the encrypted signature functions of a customer before verifying the mobile codes even in the case of the codes maliciously modified. As another way of solving th...