Abstract: A storage apparatus includes a key management unit for managing an individual key unique to the apparatus and a common key shared with other storage apparatuses, and an encryption unit for performing an encrypting process or verifying data for performing the encrypting process on electronic data stored in the apparatus to which the unit belongs using the individual key, and performing the encrypting process or verifying the data on the electronic data transmitted to or received from another apparatus using the common key. Thus, the apparatus communicates data using an applicable common key in a local environment and a global environment, appropriately manages a key in each environment, and guarantees the security of the electronic data.

Abstract: The digital signatures of users A and B are created for a transaction document which states the contents of a transaction between the users A and B, and they are sent to a transaction proof device of a notary public being a third party, together with the transaction document. Thus, the users A and B and the notary public share information, and the notary public can objectively prove the transactional contents, etc.