Patent ID: 6931537

Claim:
A time stamping system, comprising a client device and a server device; the client device including: 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; and the server device including: a plurality of time acquisition units, each time acquisition unit sequentially acquiring time information given in a prescribed constant incremental time unit, in response to the time stamping request, independently from other time acquisition units; a plurality of combining units, provided in correspondence to the plurality of time acquisition units, each combining unit generating a plurality of time stamped digital documents by sequentially combining a data containing the unified digest with the time information sequentially acquired by a corresponding one of the time acquisition units, independently from other combining units; a plurality of digital signature units, provided in correspondence to the plurality of combining units, each digital signature unit generating a digital signature for each time stamping digital document generated by a corresponding one of the combining units, independently from other digital signature units; a unified digital signature generation unit for selecting a plurality of digital signatures, one digital signature per each of the digital signature units, which are generated by the plurality of digital signature units for one time stamped digital document of an identical time, from a plurality of digital signatures generated by the plurality of digital signature units, and generating a unified digital signature from the selected digital signatures; and a time stamp token generation unit for generating the time stamp token from said one time stamped digital document and the unified digital signature generated by the unified digital signature generation unit.