Abstract: 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.

Abstract: 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.

Abstract: In a time stamping system formed by a client device and a server device, the client device includes a digest generation unit for generating a plurality of digests for a plurality of digital documents, a digest combining unit for combining the plurality of digests generated by the digest generation unit, a unified digest generation unit for generating a unified digest from the plurality of digests as combined by the digest combining unit, a transmission unit for transmitting a time stamping request containing the unified digest generated by the unified digest generation unit, to the server device, and a reception unit for receiving a time stamp token for the plurality of digital documents from the server device. The server device generates the time stamp token containing a time stamped digital document obtained by combining the unified digest and a time information acquired in response to the time stamping request, and a digital signature for the time stamped digital document.