Patent ID: 7610626

Claim:
A recording medium on which a digital stream is recorded, wherein the digital stream is associated on a segment-by-segment basis with copy control information indicating whether a segment has a Conditional Copy Freely status, the Conditional Copy Freely status indicating the segment is permitted to be freely copied on a condition that the segment is recorded in a copy destination in an encrypted form, and each segment recorded on the recording medium is in an encrypted form, the encryption being performed using a predetermined encryption key, each segment recorded on the recording medium is associated with a check code, the check code being obtained by converting the copy control information using the encryption key, and the check code has a different value depending on whether the copy control information indicates the Conditional Copy Freely status, and each check code and a corresponding copy control information are contained in each corresponding segment and recorded on the recording medium together with the digital stream, the check code being used to determine whether unauthorized tampering with the copy control information has occurred, each encryption key for a segment is calculated from three parameters, a first parameter including analog protection information for the segment, a second parameter including a time varying coefficient obtained from the segment, and a third parameter including data unique to the recording medium, the analog protection information indicates whether a copy control is applied to analog signals converted from the segment, the time varying coefficient takes on a different value depending on where the segment is located in a playback time axis of the digital stream, each segment is located on the recording medium with a predetermined offset from a location of a corresponding time varying coefficient, and the predetermined offset is determined based on a sum of time taken to calculate the encryption key from the three parameters and to obtain the check code by converting the copy control information using the encryption key.