| 摘要 |
PROBLEM TO BE SOLVED: To provide a server for giving a person in charge access permission to a determined document among documents encrypted for the person in charge of documents.SOLUTION: An encrypted text storage part 71 stores encrypted information and an encrypted first random number by using a first public key (a public key of a person in charge) and the first random number. A key reception part 74 receives from a communication terminal of the person in charge a re-encryption key for converting the encrypted information into information decryptable by a second secret key generated by using a first secret key corresponding to the first public key, the encrypted first random number, a second public key (a public key for a person in charge) and a second random number to correspond to the second public key, and the second random number encrypted by using the second public key. A conversion part 75 uses the re-encryption key to convert the encrypted information into the information decryptable by the second secret key, and replaces the encrypted information and the encrypted first random number stored in the storage part 71 with the converted information and the encrypted second random number.SELECTED DRAWING: Figure 7 |
