| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a cipher data updating system which eliminates the risk of information leakage in updating cipher data by facilitating management of a key of the cipher data, and a cipher data updating method.SOLUTION: The cipher data updating system includes a data owner PC 1 and a cloud server 2. The cloud server 2 includes: a storage part 22 storing cipher data which are encrypted by a public key in the data owner PC 1, and the public key; and a re-encryption part 23 in which re-encrypted data are generated by re-encrypting the cipher data using a new public key received from the data owner PC 1, and stored in the storage part 22 and the cipher data and the public key are deleted. The data owner PC 1 includes; a re-encryption key generation part 14 for generating a re-encryption key by combining the public key, a private key, the new public key and a new private key; and a communication part 15 for deleting the private key by transmitting the re-encryption key and the new public key to the cloud server 2.</p> |
