A storage system 1 includes a channel interface (IF) unit 11 having an interface with a server 3, a disk IF unit 16 having an interface with a hard disk unit 2 , a memory unit 21 for storing data to be read/written from/to the server 3 or the hard disk unit 2 , a switching unit 51, and the hard disk group 2. The channel IF unit 11, the disk IF unit 16, and the memory unit 21 are connected to each other through the switching unit 51, and an encryption and decryption processing unit 201 is provided between a host IF unit 101 and a transfer controller 103 in the channel IF unit 11.