A self-contained payment system uses circulating digital vouchers for the transfer of value. The system creates and transfers digital vouchers. A digital voucher has an identifying element and a dynamic log. The identifying element includes information such as the transferable value, a serial number...http://www.google.com.au/patents/US6205435?utm_source=gb-gplus-sharePatent US6205435 - Self-contained payment system with circulating digital vouchers
