Patent ID: 8312293

Claim:
An external storage device connectable to an information processing apparatus, comprising: an input/output interface via which data is exchanged with the information processing apparatus; a first storage region in which data associated with first and second validity periods is stored, the first validity period being used on condition that the external storage device is connected to one information processing apparatus, the second validity period being used on condition that the external storage device is connected to another information processing apparatus; and a second storage region in which a control program is stored, wherein the control program causes a processor to execute the steps of: establishing connection of the external storage device to an information processing apparatus via the input/output interface; identifying any one of the first and second validity periods as a validity period to be used for the data, in accordance with the information processing apparatus to which the external storage device is connected; and executing predetermined security protection processing on the data in accordance with the thus identified validity period, wherein the first validity period is encrypted with an encryption key unique to the one information processing apparatus, and the identifying step includes the steps of: attempting to decrypt the first validity period encrypted with the encryption key unique to the one information processing apparatus; and upon failure of the decryption of the first validity period, identifying the second validity period as the validity period to be applied to the data.