An information recording medium and information processing device capable
of preventing recording and reproduction of information by unauthorized
users not possessing a genuine licensed disk device. A public key for a
particular medium and a secret key are recorded on a medium and, a secret
key for deciphering the encoding is recorded on a normally inaccessible
region of the medium to prevent a user from downloading and altering the
secret key with external commands. Information encoded by the public key
of a particular device can only be decoded by the secret key of this
device or a decipher key decodable only by the secret key, and recording
or reproduction of decoded data is only possible on the genuine licensed
device, and illegal recording or reproduction of data can therefore be
prevented.
