Content protection isn’t about preventing any single failure. The actual purpose of most video and audio DRM gets missed by a lot of people. The purpose is for content owners to exert control over device manufacturers and content distribution services. It’s completely irrelevant if anyone can easily go to a torrent site and download your movie. You still get to use the legal system to force device manufacturers and distribution services to do whatever you want them to do in order to be able to play your content.

Not quite. If that were true, Blu-ray would have been quite happy with AACS. It had it all: key revocation, device-specific keys, blacklists, remote updates, it was plenty, and it even worked on the defunct HD DVD.

But they heaped on BD+ VMs, Cinavia watermarking, BD-ROM Mark, basically threw everything they had at the problem and hoped that something would stick. Movie studios actually say that Blu-ray supporting more DRM methods was actually a major reason they chose Blu-ray over HD DVD (which didn't support BD+, which supposedly was DRM designed to last a decade).

And again, if that perspective were true, the movie studios wouldn't have done the whole dance again with HDCP 2.2, BD+2, and AACSv2 when 4K Ultra HD Blu-ray came out (only for all of them to get broken again not long after release despite being completely-fresh implementations). You already needed the older versions, right? So, I would argue, it's actually a mixture of both.

Does audio DRM really exist? CDs were sold without any DRM and you can buy DRM free songs from the likes of itunes and amazon. Itunes used to have DRM but dropped it years ago; afaik songs bought from amazon never had DRM.

It's funny, songs are much easier to share than movies, the files are a hundredth the size, yet the movie industry thinks DRM is very important while the music industry survives just fine without it.

The "selling songs" music industry is basically dead, most people stream or use YouTube nowadays. Maybe that's why they don't bother with DRM? It would make them even less attractive compared to streaming

Maybe. But iTunes started phasing out DRM in 2007 and had 80% of their songs DRM-free by 2009. I think that's a few years before streaming became big. And Amazon was selling DRM-free mp3s from the big four labels in 2008.

There is a little bit of difference here though. Console copy protection usually doesn't prevent making copies of the media, rather it prevents _using_ those copies. It's more of an authentication mechanism.

OTOH, video is just pixels and waveforms. If you can get that raw content out somehow, copy protection cannot prevent someone from enjoying that copy (which can then be re-encoded to not have protection). So making video copy protection is much harder because you actually need to prevent copies rather than just make sure the authentication is hard to break.

>> which can then be re-encoded to not have protection

There are actually a handful of technologies meant to survive the transcription process only to reappear in the new medium. Probably the most effective schemes are used in money, in paper bills. There are little things there (ie the eurion constellation) that are purposely designed to be scanned. They can be copied. But then they are detected by software (Adobe Photoshop) and hardware (high-end printers) which then refuse to edit or reprint them.

https://en.wikipedia.org/wiki/EURion_constellation

Other tech is meant to leave a trail leading back to forgers, a bit like a DVD ripping software embedding your MAC/IP information in any Mp3 it generates.

https://en.wikipedia.org/wiki/Machine_Identification_Code

Persistent marks as copy protection doesn't work for media mainly because they deal with the consumption rather than copying side, so just one single non-compliant legacy device spoils the entire thing.

As for fingerprinting, that's a whole 'nother can of worms. I've never seen it be used for DRM specifically but it has been successfully used many times to track down who was leaking trade secrets etc. In fact it might be more widely deployed than most people realize.

The problem with fingerprinting for DRM would be the plausible deniability of an unsuspecting user "getting hacked" and then their fingerprinted copy ending up as the illegally distributed one without their knowledge or control.

The movie industry uses something like 'fingerprinting for DRM', adding dots to film prints sent to movie theaters to figure out where bootleg telecining is being done: https://en.wikipedia.org/wiki/Coded_anti-piracy

Does it help though? I feel like bootleg recording hasn't really been affected much...

I suppose, as long as you use locked down software and hardware. But you will be usually be able to reverse-engineer whatever heuristic they use.

>Other tech is meant to leave a trail leading back to forgers, a bit like a DVD ripping software embedding your MAC/IP information in any Mp3 it generates.

It is simple: rip the media multiple times with different identifying information, and then analyze the diffs (or just take the average). You cannot hide the existence of steganographic data if there are multiple copies with different steganographic data. It is not like analog where a loss of precision is justifiable