FWIW - The DVD CSS scheme is build upon a couple of LFSRs. They're then combined in 4 different ways (XOR of the streams, as is or inverted). Three of the comb

FWIW - The DVD CSS scheme is build upon a couple of LFSRs. They're then combined in 4 different ways (XOR of the streams, as is or inverted). Three of the combinations are used for the "authentication" portion (as used by s/w), the other combination for the "encryption" portion.