US Patent 7634653 Event-ordering certification method

An event-ordering certification system 100 includes a certification apparatus 1, a plurality of user apparatuses 2i (i=a, b, . . . , n), an audit apparatus 3 for performing an audit of an event-ordering receipt published by the certification apparatus 1 and a network 4 for connecting these elements with each other. In response to an event-ordering request from one user apparatus 2i, the certification apparatus 1 publishes the event-ordering receipt and sends it to the user apparatus 2i. If a mistrust is produced in the event-ordering receipt, the user apparatus 2i verifies the event-ordering receipt with the use of data published by the certification apparatus 1 and an audit result by the audit apparatus 3.