Anonymous and Fair Micropayment Scheme with Protection against Coupon Theft

Abstract

The development of new applications of electronic commerce (e-commerce) that require the payment of small amounts of money to purchase services or goods opens new challenges in the security and privacy fields. These payments are called micropayments and they provide a trade-off between efficiency and security requirements to pay low-value items. It is usual to assume low value fraud to achieve efficiency in micropayment systems. In this paper the authors present an improved version of an efficient and secure micropayment scheme which fulfils the security properties that guarantee no financial risk for merchants and the privacy of the customers. In addition, the proposed system defines a fair exchange between the coin and the desired good or service. In this fair exchange, the anonymity and untraceability of the customers are assured. Moreover, customers can request a refund whether they are no more interested on the services offered by merchants. As a novelty, an improvement of the scheme avoids customers to fraudulently use a refund operation to gain a little amount of money (called coupon). Thus, a new resolution subprotocol allows the merchant to avoid the loss of any single coupon.