Patent ID: 7647646

Claim:
An information input/output system, comprising: a recording medium that stores: (i) content encrypted using a media key, (ii) an encrypted media key generated by encrypting the media key using a device key, (iii) invalid-device information including identification information identifying one or more invalid input/output devices that have been made invalid for use, and (iv) verification data, which is generated through a one-way conversion that is dependent on at least the media key and the invalid-device information, such that predetermined verification processing performed on the verification data fails when either (a) the encrypted media key is tampered with or (b) the invalid-device information is tampered with; an input/output device that includes: a storing unit that stores identification information that identifies the input/output device, a read unit that reads the encrypted content, the encrypted media key, the invalid-device information, and the verification data from the recording medium, and a transmission unit that transmits the encrypted content, the encrypted media key, the invalid-device information, the identification information of the input/output device, and the verification data; and a host device that includes: a storage unit that stores the device key, a receiving unit that receives the encrypted content, the encrypted media key, the invalid-device information, the identification information of the input/output device and the verification data from the input/output device, a verification unit that performs, through the one-way conversion that is dependent on at least the media key and the invalid-device information, the predetermined verification processing on the verification data in order to verify that neither the received encrypted media key nor the received invalid-device information has been tampered with; a confirmation unit that, when the verification unit succeeds in the predetermined verification processing, confirms whether or not the input/output device has been made invalid by checking whether or not the received identification information of the input/output device is included in the received invalid-device information, a first decryption unit that decrypts the encrypted media key, using the device key, and a second decryption unit that decrypts the encrypted content using the media key when (i) the verification unit succeeds in the predetermined verification processing; and (ii) the confirmation unit confirms that the input/output device has not been made invalid.