Cinavia DRM: How I Learned to Stop Worrying and Love Blu-ray’s Self-Destruction
by Ganesh T S on March 21, 2012 11:00 AM EST- Posted in
- Home Theater
- Blu-Ray
- DRM
- Cinavia
Content providers mandate the presence of protection schemes at all times when the consumers want to access their wares. For the consumer, this entails:
1. Conditional access
2. Protected transmission
3. Protected distribution
4. Protected storage
Conditional access is applicable to cases where media travels over insecure channels (such as satellite or cable). This is implemented in STBs. Protected transmission is the path to the display device, and it is usually protected by HDCP (over HDMI) or Macrovision in legacy systems. Protected storage is encountered in broadcast content, with its copy flags to allow DVR archiving. Protected distribution is enabled by the DRM mechanism in Blu-rays / DVDs. In Blu-rays, this DRM scheme is called as AACS (Advanced Access Content System). AACS also provides for protected storage through the Managed Copy feature.
A Popular Webcomic's Take on DRM (c) xkcd
AACS uses 128-bit AES for encryption. Each Blu-ray player / device has a Device Key, while discs come with a Media Key Block (MKB). The shared key generated by using these two (Media Key) is used to decrypt the Title Key, which is then used to decrypt the audio/video data in the disc. AACS also has a revocation mechanism. The MKB in each disc has a Host Revocation List for software players and a Device Revocation List for hardware drives. For PC-based playback to be successful, both the player and the drive must not be on the revocation list.
In practice, key revocation is quite rare because device keys could be shared across an entire lineup, making it hard to pinpoint which particular device was compromised. AACS does provide some sequence keys to identify a particular device as compromised if one has access to multiple pirated copies of different discs from the same drive. In addition to the MKB-Media Key-Title Key combination, PC-based players also have support to generate a Shared Bus Key to encrypt the data inbetween the drive and the software player. This ensures that any snooped data can't be used to get to the original content on the disc. AACS also has a renewal process to prevent attacks similar to those carried out on CSS (with DVDs). The net result is that we are currently at AACS v30.
In addition to AACS, the BDA mandates a BD-ROM mark, which is a physical irregularity on the disc with a 128-bit VolumeID. Blu-ray players will not play back protected content without the VolumeID, as it is essential to the decryption process. Also, the VolumeID can't be generated by consumers (BD-Recorders don't have the capability to burn a VolumeID). The process is tied to the manufacturing facility (which can obtain a license only under strict security considerations). With a counterfeit Blu-ray, it is a simple matter of using the VolumeID to trace the place where the piracy took place.
Note that AACS is based solely on cryptography and, after having been compromised, has the possibility of revoking cryptographic keys as the only means of regaining its effectiveness. So far, this method has failed. This has tempted studios to move over to other forms of DRM such as BD+ and Sony Screen Pass.
It is mandatory for players to implement support for BD+, but not all Blu-rays need to be BD+ enabled. From a player's perspective, a Security Virtual Machine (SVM) needs to be implemented. Blu-rays with BD+ have special content code which are loaded by the SVM and executed during the playback process. The content code has full control over all the components involved in playback. It can alter menus and show on-screen messages if some security breach is detected in the player.
One of the most common BD+ implementations involves storing garbled video on the disc (i.e, after AACS decryption, certain segments of the video are distorted). The content code can implement a fix for the distorted video so that licensed playback is still problem free. For example, in the recently released Contagion Blu-ray, watching the disc with an old version of AnyDVD HD (which performs only AACS decryption, say) would result in heavily distorted video in various scenes. This is because the BD+ code to fix the video wasn't being executed by AnyDVD HD. Unlike AACS, technologies such as BD+ from Irdeto (responsible for the BD+ in the Contagion Blu-ray) and Sony Screen Pass continue to evolve with each new disc.
BD+ needs a SVM to be implemented, but note that the Blu-ray specifications already include a VM requirement for the BD-Java feature. This BD-J feature can also be used to implement structural protection schemes such as Sony DADC's Screen Pass. In this scheme, BD-J code on the disc actively looks for signs of protection being in place during playback. When the BD-J code finds that the protection features are missing (say, due to playing an unprotected copy, or when ripping tools are active in the background), playback is immediately stopped along with an on-screen message. DVDFab's blog has some more details on Screen Pass.
In addition to DRMs aimed at directly protecting content by encryption, the Blu-ray developers also considered some watermarking schemes. Watermarking doesn't actually encrypt the content, but places some non-discernible (to the naked eyes/ears) information in the audio / video tracks of the stream. By serving as a digital signature, it helps the player / analyzer identify the content status. In the next section, we will be talking in detail about Cinavia, the audio watermarking scheme from Verance. Thomson's NexGuard is a type of video watermarking scheme which works with the help of the BD+ SVM. The BD+ content code embeds some invisible information in the video track which contains details of the player / drive used to decrypt the stream. If the video gets out and becomes a 'pirated copy', the watermark can be analyzed to determine the player / drive responsible for the 'piracy'. BD+ code in subsequent Blu-rays can be used to blacklist the player / add it to a revocation list.
If you are interested in learning more about content protection in Blu-rays, I strongly suggest perusing Chapter 4 of Blu-ray Disc Demystified.
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Exodite - Wednesday, March 21, 2012 - link
Ditto for Sweden.I often lament the complete lack of legal, and convenient, ways of accessing digital media.
I pay for cable access but frankly I download all my shows as it's simply that much more convenient.
I wouldn't mind paying a reasonable amount, say what I'm currently paying for cable, for access to digital media in a timely and convenient manner.
It's not happening though, which is why my shows come off the 'net and my movies are bought in hard-copy Blu-rays.
Penti - Friday, March 23, 2012 - link
Lovefilm is pretty much none existent no matter country. You can pretty much forget about any such service in EU/EEA, it's to regionalized and oligopoly oriented which basically forms distribution monopolies not even Mussolini could fatom, it's further exacerbated by the music rights which is also negotiated at a national level making it impossible to even stream stuff you own the rights for to different countries, all at national levels and too many content distributors to deal with. It's the only one field that isn't fully included in the common market. Any other service, software, games and books is fine doing cross border with no local agreements at all. Amazon sells us EU citizens about 1 million ebooks for example. I think Lovefilm in UK where most movie and TV rights go trough when they are sold to us, still has about 6000 titles on the streaming instant on version. It's nothing nothing at all compared to Amazons over 100 000 titles in the states.Even if companies in London say sell TV-rights to another country there are still some shows/networks that will have local distributors where they have been granted a monopoly over a region making it impossible to get the rights for your territory and means you can't just go to the creators and official distributors and so on. Companies in London sometimes even releases DVD's with Scandinavian subtitles but aren't allowed to sell their own movies/releases in those countries if somebody else own the regional rights, which means they might not end up doing a release at all or will be doing their own technical inferior one. Subtitling is definitively not an issue at all here.
Services with 2000-6000 titles is pretty much useless, you can't subscribe to your favorite show or see the movies you like. Your better of subscribe to some physical dvd/bd disc rental service where the offering is better. I don't know of a EU country where that isn't true at least. In US Netflix physical service of course has worse catalog then Amazon VOD and Netflix on-demand offerings.
Johnmcl7 - Wednesday, March 21, 2012 - link
Netflix has just launched here and the pricing is very good but the selection unfortunately isn't, Lovefilm instant are meant to have a slightly better selection but the market is still quite a bit behind the US. I prefer buying my films on blu-ray for the quality and not having to worry about bandwidth but I could certainly see myself using something like Netflix for films I fancy watching as one-offs.John
LancerVI - Wednesday, March 21, 2012 - link
I agree. They are promoting their own death.Ten years from now, physical media will be all but gone IMHO.
Maybe they want it this way. After all, streaming gives absolute control of the content to the provider, not the consumer.
Anonymous Blowhard - Wednesday, March 21, 2012 - link
> Maybe they want it this way. After all, streaming gives absolute control of the content to the provider, not the consumer.Bingo. They'd rather you rent it every time you want to watch it than be able to buy once and watch it forever (after the requisite 15 minutes of unskippable preview, fluff, FBI warnings, etc. See the "pirate dvd" image below :) )
Hrel - Wednesday, March 21, 2012 - link
If you are displaying it on a screen, streaming from the internet, local network, secured VPN, DVD, Blu Ray or anything else. You can make a copy of that movie in full quality. That's the bottom line, there's literally nothing you can do to stop that.If the filthy rich movie studios want to stay in business they need to just "trust" (Huh, I KNOW what a fucking concept) that the people who can afford to pay for their content will. Because they honestly WANT to support the people who made the content they like, and want more of it. This means no DRM of any kind, it doesn't work, so it's just a waste of money. And, this is the big one, lowering prices. A LOT. I don't mean instead of releasing at 25 dollars USD release at 20, I mean release at 5, and let it drop RAPIDLY!!!
Get with the times. I don't even own DVD's anymore, I have 6TB of external storage, with redundancy. I don't want 5000 physical cases laying around my house when I can have ONE NAS. If there's no physical media to buy, just a digital copy you download off the internet. That means there's less cost. No disc, no case, no artwork for either. No shipping and no middle man. (The retailer selling the physical media). Meaning digital copies should be quite a bit cheaper, not the same price, not even close.
It seems like perfectly clear common sense to me, and everyone I've seen on reddit or any other online forum. How out of touch do studio execs have to be to continue trying to hold on to how things were in the mid 1900's and on? Seriously, it's 2012, move on.
cmdrdredd - Wednesday, March 21, 2012 - link
no....Stream dual 1080p video for 3D with a DTS-HD MA audio track and then MAYBE....You can't stream that off netflix or hulu. The bandwidth coming from a Blu-Ray is much higher than you could stream on most internet connections.
" The net result is that almost every new Blu-ray fails to play back on a player if it doesn’t have the latest firmware updates."
Wrong buddy...I have a first gen Samsung Blu-Ray player and haven't ever once had a disk not play. Some load slowly, but that's because the drive is not as speedy as newer models. Everything works though and always has.
Botia - Wednesday, March 21, 2012 - link
I have started timing how long it takes to get bluray movies to play from the time the disc is inserted until the time when the main movie is playing. Any thing possible to speed up the process is done, such as using the disc menu, next track, fast forward, etc.What I have found is that it takes on average 15 minutes to start a movie. In our age of instant gratification this is nauseating. One movie took 2 hours before giving up. It insisted on downloading previews from the Internet and playing them. While the picture and sound quality is significantly better than other media, the user experience is so far behind. How do they expect to survive?
One special note, Transformers: Dark of the Moon started up almost immediately. Thank you!
Colin1497 - Wednesday, March 21, 2012 - link
We actually got a movie the other day that wouldn't let us skip ANY of the previews, and to top it off, we were interrupted watching it had to reboot it and wait through all the previews a second time. The studios really know how to make everyone hate them.superccs - Wednesday, March 21, 2012 - link
It takes less effort to pirate the movie you want to watch then to get it through any other source.This is like going to a nice expensive restaurant not get seated promptly, having the service suck, and food take forever. So you go home and make whatever you originally wanted off their menu and tip yourself handsomely.
Why should anyone pay for an inferior product/service especially when you are trying to attract the business of a bunch of cooks.