Recording medium, recording apparatus, reading apparatus, and program and method therefore

A recording apparatus comprising:

• a judging unit operable to judge a copy attribute of signals inputted from an external source, the signals representing a segment of a digital stream;
• a writing unit operable to write, when the copy attribute indicates that the segment is conditionally permitted to be freely copied, the segment onto a recording medium in association with copy control information indicating a Conditional Copy Freely status, the Condition Copy Freely status indicating that the segment is permitted to be freely copied on a condition that the segment is recorded in a copy destination in encrypted form;
• and
• an encrypting unit operable to encrypt the segment using a predetermined encryption key, wherein
• said writing unit writes the encrypted segment on the recording medium in association with a check code,
• the check code is 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 code control information has occurred,
• each encryption key for a segment is calculated from three parameters, a first parameter being analog protection information for the segment, a second parameter being a time varying coefficient obtained from the segment, and a third parameter being 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 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.

A duplicating apparatus for copying a digital stream recorded on a source recording medium to a destination recording medium, comprising:

• a reading unit operable to read from the source recording medium a segment of the digital stream and copy control information associated with the segment, the digital stream being in encrypted form;
• a decrypting unit operable to (1) generate a check code, (2) compare the generated check code with a check code that is pre-recorded in the source recording medium, and (3) when the two check codes match, decrypt using an encryption key the segment read by said reading unit, the encryption key being unique to the source recording medium;
• an encrypting unit operable to encrypt the decrypted segment using an encryption key unique to the destination recording medium;
• and
• a writing unit operable to write, when the copy control information indicates a Conditional Copy Freely status, the encrypted segment onto the destination recording medium in association with the copy control information, wherein
• the generation of the check code is performed by encrypting the copy control information using the encryption key, and the check code has 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 destination 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.