Technical Report TR-98-13, LCIS, Tamkang University, Taiwan, R.O.C., July 1998.

Abstract. Both PayWord and Millicent are quite efficient micropayment systems. There are some differences and similarities between them, however no article in the open literature has ever given research result on these issues for the two systems. In this report, comparisons of PayWord and Millicent will be given, especially when both systems will be implemented in a cryptographic portable device, e.g., smart IC cards.