Encryption key management system and encryption key management method

An encryption key management system, comprising:

• a storage apparatus that encrypts data with one or more encryption keys and stores the encrypted data;
• and
• one or more key management servers connected to the storage apparatus through a network,
• wherein each of the key management servers holds one or more key encryption keys for encrypting the encryption keys together with its attribute information,
• the storage apparatus holds the encryption keys encrypted by the key encryption keys,
• the storage apparatus sends a request for the key encryption key corresponding to the storage apparatus to the key management server using a storage apparatus ID for uniquely identifying the storage apparatus as a parameter,
• the storage apparatus acquires the key encryption key corresponding to the storage apparatus and its attribute information from the key management server,
• the storage apparatus stores the key encryption key and its attribute information in a key encryption key list while eliminating the key encryption key that is duplicated,
• the attribute information includes a generation date and time of the key encryption key,
• in the key encryption key list, the key encryption keys are arranged in order of a new generation date and time,
• the storage apparatus stores a key management server number that specifies a key encryption key to acquire the key encryption key corresponding to the storage apparatus,
• when there is the same key management server number, the storage apparatus sets a key encryption key having a new generation date and time as a key encryption key for update and sets a key encryption key having a next generation date and time as an old key encryption key in order of a generation date and time and attempts decryption using the old key encryption key,
• when there is no same key management server number, the storage apparatus sets the key encryption key stored in the key encryption key list as an old key encryption key, requests the key management server to generate a new key encryption key for update, and acquires the key encryption key for update,
• the storage apparatus determines a success or failure of the decryption using the old key encryption key, and encrypts the decrypted encryption key with the key encryption key for update when the decryption using the old key encryption key is successful,
• when there is the same key management server number, the storage apparatus requests the key management server to delete key encryption keys other than the key encryption key for update, and
• when there is no same key management server number, the storage apparatus requests the key management server to delete key encryption keys stored in the key encryption key list.

An encryption key management method using an encryption key management system in which a storage apparatus that encrypts data with one or more encryption keys and stores the encrypted data is connected to one or more key management servers through a network, the method comprising:

• a step in which each of the key management servers holds one or more key encryption keys for encrypting the encryption keys together with its attribute information;
• a step in which the storage apparatus sends a request for the key encryption key to the key management server using a storage apparatus ID for uniquely identifying the storage apparatus as a parameter;
• a step in which the storage apparatus holds the encryption keys encrypted by the key encryption keys;
• a step in which the storage apparatus sends a request for the key encryption key corresponding to the storage apparatus to the key management server using a storage apparatus ID for uniquely identifying the storage apparatus as a parameter;
• a step in which the storage apparatus acquires the key encryption key, for which a request has been sent to the key management server, and its attribute information;
• a step in which the storage apparatus stores the key encryption key and its attribute information in a key encryption key list while eliminating the key encryption key that is duplicated;
• a step in which the storage apparatus attempts to decrypt the encryption key using the key encryption key stored in the key encryption key list;
• and
• a step in which the storage apparatus determines a success or failure of the decryption of the encryption key and attempts to decrypt the encryption key using the key encryption key stored in the key encryption key list, which has not been attempted yet, when the decryption of the encryption key using the key encryption key fails.