Fair Micropayment System Based on Hash Chains

Micropayment schemes usually do not provide fairness, which means that either the customer or the merchant, or both, can cheat each other and gain a financial advantage by misusing the protocols. This paper proposes an efficient hash chain-based micropayment scheme, which is an offline, prepaid scheme that supports simpler divisibility of digital coins. In the execution of payment protocol, the customer's disbursement and the merchant's submittal are performed step by step, whoever cannot gain addition profits even if he breaks off the transaction. The hash chain can also be used for transactions with different merchants. Unlike other micropayment schemes, e.g., PayWord, no public-key operation is required, which improves the efficiency. The scheme also provides restricted anonymity.