The most important technical problem in EC is about secure electronic payment systems. Electronic payment systems come three different types distinguished by the payment method: electronic cash, electronic check, and creditcard. In these types, electronic cash payment system is popular and practical as in real commerce. But electronic cash can be copied easily, then it is infeasible to prevent user from double-spending a coin. In this paper, we overview several requirements for secure electronic payment system and present other proposed additions to the results. At last we present a model system which considers requirements above examined.