Patent ID: 8850207

Claim:
A host storing host key information and host certification information stored therein, the host comprising: a processing circuit configured to generate a first random number, and send to a medium the first random number and the host certification information with first signature information attached thereto, the first random number being used at the medium in a signature process using medium key information; receive, from the medium, a second random number, medium certification information stored in the medium, a first value calculated using a third random number different from the second random number and a base point of an elliptic curve, and unique ID information generated by executing a one-way function calculation based on controller key information and controller identification information stored in the medium; verify second signature information attached to the medium certification sent from the medium; generate a fourth random number, and calculate a second value using the fourth random number and the base point of the elliptic curve; perform a signature process for the second value and the second random number sent from the medium, using the host key information; and generate shared key information shared by a key exchange process between the host and the medium.