Patent ID: 7783895

Claim:
A host device operative to input data to a removable storage device provided with a first encryption unit and output data from the storage device, the host device comprising: a second encryption unit configured to perform a host-device side process of a series of cryptographic processing for encrypting data to be secured; and a controller which divides the series of cryptographic processing into a plurality of procedures, and divides the plurality of procedures into procedures to be executed in the first encryption unit and procedures to be executed in the second encryption unit, and issues to the storage device a command for controlling the first encryption unit to execute the procedures to be executed in the first encryption unit, wherein the controller obtains information for estimating time necessary to execute the command from the storage device prior to the issuance of the command, sets a wait time for the command based on the obtained information, issues the command to the storage device via a bus electrically connecting the host device and the storage device, releases the bus for another command, and waits the time set for the command before it issues a command for the next procedure to the storage device, in order to have the next procedure executed by the first encryption unit, and wherein the information for estimation is selected from the group consisting of a typical processing time, an average processing time, and a maximum processing time necessary to execute the command.