[ktta]

CSS[1] was the defacto 'DRM' back in the day, which used two LFSRs for 40-bit encryption. Apart from being able to brute force it today, there are many other ways to break it[2].

Now the DRM on DVDs/BluRays is AACS[3], which uses AES. You might also recognise it from the 'copyrighted numbers' fiasco[4]

[1]: https://en.wikipedia.org/wiki/Content_Scramble_System

[2]: https://en.wikipedia.org/wiki/Content_Scramble_System#Crypta...

[3]: https://en.wikipedia.org/wiki/Advanced_Access_Content_System

[4]: https://en.wikipedia.org/wiki/AACS_encryption_key_controvers...