Patent ID: 7996914

Claim:
A semiconductor memory card for attaching to and detaching from an electronic device having a unique identifier, the semiconductor memory card comprising: a rewritable nonvolatile memory including (i) an authentication area, which is accessible by the electronic device only when the electronic device is authenticated, and which stores an encryption key, and (ii) a non-authentication area, which is accessible by the electronic device regardless of whether or not the electronic device is authenticated, and which stores encrypted data to be decrypted using the encryption key; an authentication unit operable to perform an authentication process, when the semiconductor memory card attaches to the electronic device, to check whether or not the electronic device is authentic; and an authentication area access control unit operable to permit the electronic device to access the authentication area only when the authentication unit affirmatively authenticates the electronic device, wherein the authentication unit includes: a device identifier group storage unit operable to store one or more first device identifiers that are unique to one or more electronic devices that have been confirmed to be authentic through a mutual authentication between the semiconductor memory card and a respective electronic device; a user key storage unit operable to store a first user key; an obtaining unit operable to obtain a second device identifier that is unique to the electronic device or a second user key from the electronic device; a first comparison unit operable to (i) perform a comparison between the one or more first device identifiers stored in the device identifier group storage unit and the obtained second device identifier, to check whether or not any of the one or more first device identifiers is identical to the obtained second device identifier, (ii) judge that the electronic device is authentic when any of the one or more first device identifiers is identical to the obtained second device identifier, and (iii) request a user of the electronic device to input the second user key when none of the one or more first device identifiers is identical to the obtained second device identifier; a second comparison unit operable to perform a comparison to (i) judge whether or not the first user key stored in the user key storage unit is identical to the obtained second user key, (ii) judge that the electronic device is authentic when the first user key is identical to the obtained second user key, and (iii) judge that the electronic device is not authentic when the first user key is not identical to the obtained second user key; and a writing unit operable to write the second device identifier into the device identifier group storage unit when the second comparison unit judges that the electronic device is authentic.