A technology is provided to improve tamper resistance in encrypting data to be secured and inputting/outputting the data between a recording device and a host device. When the recording device issues an input/output command to a storage device to input/output data to be secured, the recording device attaches an ID to the command to identify to which cryptographic input/output processing the command belongs. Upon reception of a sequence command, the storage device receives the command if its ID has been allocated and the command is verified to have been issued in the correct sequence. The sequence ID is used to identify a process system while appropriately managing the steps of executing commands.