| 摘要 |
A time stamp obtaining apparatus for maintaining the certificate of the existence of electronic filing document including: a receiving unit 12 receiving hash value of the document data; a transmitting section 15 c transmitting the hash value to time stamp providing apparatus 30 a; a storing processing section 15 d inserting the time stamp encoded with private key in unupdated data 16 b concerning time stamp received since point to which private key is updated and storing; an update detecting section 11 detecting the update of private key; a calculation section 13 b calculating hash value for all time stamps included in the unupdated data 16 b; a transmitting section 13 c transmitting the hash value; a storing processing section 13 d moving the unupdated data 16 b to past data 16 c concerning time stamp received before point to which private key is updated last time when time stamp is received, storing it, and storing the time stamp newly received as new unupdated data 16 b; is provided.
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