AACS

Advanced Access Content System
One of my job is to implement the security system to fullfill the AACS requirement.
AACS is the more up-to-date version of CPRM, which is not very popular. The idea is to encrypt the content using very strong encryption, and the embed the key on the disc. Only valid software plus valid drive can retrieve the key and then playback properly. If the software or drive is hacked to do anything AACS doesn't like, it is revoked.
The software can be hacked to produce perfect unencrypted AV stream. The drive can be hacked to produce or accept perfect copies.

The revokation mechanism is doomed to failure, with an open platform like our PC. You have to know who to revoke in the first place. They do have forensic mark mechanism, but I do not believe it would work, either.

The problem for AACS is the copy-protection part is too strong, and the on-line transaction part is too weakly addressed. People would have to replace their digital TVs and LCD monitors to watch HD content, but no any player, sw or hw, supports any new transaction model till today.