A pay word-based micropayment protocol supporting multiple payments

In this paper, we propose an efficient micropayment protocol by improving PayWord, which is one of the representative micropayment protocols. In the original PayWord system, it was designed for a customer who generates paywords by performing hash chain operation for payments to an only designated vendor. In other words, the customer has to create new paywords in order to establish commercial transactions with different vendors on the Internet. To supplement this drawback, our proposed scheme provides a useful method to do business with multiple vendors for a customer with only one hash chain operation. In our proposed protocol, a broker creates a new series of hash chain values along with a certificate for the certificate request of a customer. This certificate is signed by the broker to give authority enabling the customer to make paywords. Our proposed scheme provides an efficient means for the customer to do business with multiple vendors.