Researches on the secure e-cash system have been carried on with the proliferation of the Internet and e-commerce. Subsequently, various systems and schemes have been proposed in the literature.
Micro-payment systems have been proposed for small and frequent payment such as database query, software, and e-news different from the established payment system (so called Macro-payment). Micro-payment system is considered to be proper for areas where efficiency is the most critical factor. Because the overhead cost for card company is higher than the price of goods, and the processing time related to public key computation is required too much, most of the previous systems exclude public key computation or admit the minimal computational overhead for efficiency.
From the security point of view, micro-payment system is mainly concerned about preventing or detecting from double spending and forgery.
Assurance of atomicity is strictly needed as well to resolve potential problems, for example, the loss of money from the network failure.
In this thesis, we propose a new micro-payment system that satisfies basic requirements of micro-payment systems and atomicity. Explicitly, this system can be considered as an improvement and extension of PayWord is one of the most popular micro-payment systems suggested by Rivest and Shamir.
Our proposed system makes use of only one hash but is applicable to multiple vendors. Since PayWord requires using each hash chain for each vendor, the customer has to maintain all indices after dealing with vendors. To solve this problem, we use a receipt which includes a signature of vendor. The customer uses this signature for different vendors to enable them to verify whether the starting index of payment is correct or not. Moreover, we focus on the system that guarantees atomicity and non-repudiation among requirements for payment systems. Atomicity and non-repudiation play an important role in payment systems. In particular, atomi...