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SERVER APPARATUS AND PROGRAM

  • US 20140208117A1
  • Filed: 03/19/2014
  • Published: 07/24/2014
  • Est. Priority Date: 09/30/2011
  • Status: Active Grant
First Claim
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1. A server apparatus configured to re-encrypt ciphertext data obtained by encrypting plain text data with an administrator public key, without decrypting the ciphertext data and to store a re-encryption key for obtaining re-encrypted text data able to be decrypted with the user private keys of user apparatuses, the server apparatus comprising:

  • a storage device which stores the re-encryption key generated on the basis of an administrator private key associated with the administrator public key, and a user public key associated with the user private key;

    a transmitting/receiving device which transmits the re-encryption key to a user apparatus on receiving from the user apparatus a notification showing that the re-encryption key should be updated, and receives an updated re-encryption key calculated from the re-encryption key on the basis of the user private key not updated and the updated user private key; and

    a replacing device which replaces the re-encryption key stored in the storage device with the updated re-encryption key.

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