10. An electronic document storage apparatus for storing an electronic document, comprising: an electronic document storage unit for storing the registered electronic document for a specified period of time; an electronic document management unit for storing at least a status, a date of registration and an access history of the registered electronic document; a key management unit, including an encryption key creation part for creating a pair of keys made up of encryption keys by a public key encryption system and a for-management key table for managing the pair of keys created by the encryption key creation part through assigning key ID as a load key for one of the pair of keys and a read key for the other thereof, for enciphering by using the load key when there is a request for enciphering; a media management table for recording management information of an archive media being used for transferring the electronic document; a transfer process unit for transferring to an archive media an electronic document registered prior to a defined date from among the electronic documents registered in the electronic document storage unit following a request to the key management unit for enciphering the electronic document and storing management information of an archive media used for transfer including the key ID of a used encryption key in the media management table; a for-reference management information extraction unit, when receiving a request for referring to an electronic document transferred to the archive media on an apparatus other than the electronic document storage apparatus, for extracting information including a key ID of an encryption key used at the time of transferring the electronic document required for referring thereto by searching the electronic document management unit and the media management table; a key management unit decodes reference history information encoded by an electronic document reference apparatus and stored in the archive media, by using a write key paired with a read key used for encoding the reference history information, where the reference history information indicates reference to the electronic document, and wherein a hash value of the electronic document is calculated, and after encoding the calculated hash value using the write key used when the key management unit encodes the electronic document, the encoded hash value is stored in the archive media, and the electronic document reference apparatus calculates a hash value of the electronic document stored in the archive media, and decodes the electronic document stored in the archive media using the read key stored in a for-reference management information emigration media when the calculated hash value matches a hash value obtained by decoding the hash value stored in the archive media using the read key stored in the for-reference management information emigration media, and the write key and the read key are configured to be changed at a specified timing, and the electronic document reference apparatus decodes the electronic document stored in the archive media by using the read key paired with the write key used when the electronic document was transferred by the transfer process unit.
10. An electronic document storage apparatus for storing an electronic document, comprising: an electronic document storage unit for storing the registered electronic document for a specified period of time; an electronic document management unit for storing at least a status, a date of registration and an access history of the registered electronic document; a key management unit, including an encryption key creation part for creating a pair of keys made up of encryption keys by a public key encryption system and a for-management key table for managing the pair of keys created by the encryption key creation part through assigning key ID as a load key for one of the pair of keys and a read key for the other thereof, for enciphering by using the load key when there is a request for enciphering; a media management table for recording management information of an archive media being used for transferring the electronic document; a transfer process unit for transferring to an archive media an electronic document registered prior to a defined date from among the electronic documents registered in the electronic document storage unit following a request to the key management unit for enciphering the electronic document and storing management information of an archive media used for transfer including the key ID of a used encryption key in the media management table; a for-reference management information extraction unit, when receiving a request for referring to an electronic document transferred to the archive media on an apparatus other than the electronic document storage apparatus, for extracting information including a key ID of an encryption key used at the time of transferring the electronic document required for referring thereto by searching the electronic document management unit and the media management table; a key management unit decodes reference history information encoded by an electronic document reference apparatus and stored in the archive media, by using a write key paired with a read key used for encoding the reference history information, where the reference history information indicates reference to the electronic document, and wherein a hash value of the electronic document is calculated, and after encoding the calculated hash value using the write key used when the key management unit encodes the electronic document, the encoded hash value is stored in the archive media, and the electronic document reference apparatus calculates a hash value of the electronic document stored in the archive media, and decodes the electronic document stored in the archive media using the read key stored in a for-reference management information emigration media when the calculated hash value matches a hash value obtained by decoding the hash value stored in the archive media using the read key stored in the for-reference management information emigration media, and the write key and the read key are configured to be changed at a specified timing, and the electronic document reference apparatus decodes the electronic document stored in the archive media by using the read key paired with the write key used when the electronic document was transferred by the transfer process unit. 11. The electronic document storage apparatus according to claim 10 , wherein said for-reference management information extraction unit receives a load key used for enciphering and the pairing read key by requesting said key management unit for enciphering said extracted information by specifying said key ID, and stores the enciphered extracted information and the received read key in said for-reference information emigration media for emigrating to an apparatus other than the electronic document storage apparatus.