ENCRYPTED DATA STORAGE SERVER SYSTEM, ENCRYPTED DATA STORAGE METHOD, AND RE-ENCRYPTION METHOD

摘要

PROBLEM TO BE SOLVED: To provide an encrypted data storage server system with high secrecy so as not to impose much load on users. SOLUTION: The user 41 transmits only a difference between a new key and an old key for re-encryption to a proxy server 20. The proxy server 20 directly applies re-encryption to encrypted data by using only the difference of the transmitted keys without decoding the encrypted data stored in a storage server 10. The storage server 10 stores the encrypted data re-encrypted by the proxy server 20. COPYRIGHT: (C)2005,JPO&NCIPI