the HDCP faq thread

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Matthias99

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Oct 7, 2003
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Originally posted by: Janooo
Originally posted by: Matthias99
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What devices? Breaking the encryption in general would require inside knowledge of the protocol (which, unless someone in the know leaks the information, is essentially impossible to get). It uses per-session encryption keys (unlike DSS), so it's not a 'break it once, break it forever' type of system. I get the feeling when these discussions come up that a lot of people are simply in denial about the whole thing.

...

A piece of HW that goes to HDCP TV can be used in a HDCP -> component converter. How difficult it can be?
Unless this HW is serialized and tracked there is no way it can be prevented.

What 'piece of hardware'? The proprietary encryption chip using an encrypted proprietary protocol that you don't know how to interpret? Yeah. Good luck with that.
 

Matthias99

Diamond Member
Oct 7, 2003
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First -- you suck at teh quoting. I fixed this post; please try not to mangle it so badly. It's very hard to read posts when things aren't quoted properly.

Originally posted by: niggles
Originally posted by: Matthias99
Originally posted by: niggles
there's already been a lengthy thread on this topic. 2 things come to mind from that topic.

1. this is not acceptable, don't support it by giving money until they drop the ridiculous requirement to register your monitor.

There's no "requirement to register your monitor". Yeesh. There's enough FUD going around about HDCP already. It's an encryption spec at the player/display level.

Sorry, totally worded incorrectly. What I meant was that you file only works with your montiors serial number, not simply because your monitor is set to allow the file, it has to register the the file against the serial number of the monitor. It will not play on another monitor

I've never heard of this 'feature'. Source?

What HDCP does is to provide end-to-end encryption between a media source and a playback device. Anything beyond that is being done by a higher-level protocol.

2. It'll get cracked just like everything else and they'll have to get rid of it.

Um, no, this one probably won't. At least not very quickly. Anyone saying otherwise doesn't have a real good grasp of what it is and how it works.

Anything can be cracked, it simply comes down to time and energy. In this particular case it came down to the energy that would have to be exerted. Like I said, this has been heavily discussed. For your reading pleasure I found the thread for you so you can read the arguments for and against: http://forums.anandtech.com/messageview...hreadid=1639479&enterthread=y&arctab=y
The thing about my post you should note is that these were options on the subject.

Yes, obviously, any type of encryption can be broken given enough time and effort. However, there does not appear to be any obvious way to 'break' HDCP encryption other than brute force or having inside knowledge about the protocol.

There's very little in that thread (which I have seen before) relating to the subject. In fact, the OP seemed to be blaming Microsoft for HDCP, when MS really has nothing to do with it other than that Vista will be capable of playing HDCP-encrypted content if you have a monitor that supports it.


3. There's nothing anyone can do, don't by *any* new hardware until it comes out

It's already supported by the VAST majority of HDTV sets. It's only computer monitors that have been lacking.
It's the fact that it forces anyone with a PC to buy new hardware if they want to view this media. It's a bad implementation, they should figure something else out for PCs that doesn't involve forcing people who have paid a lot of money for their hardware to go out and buy it all over again.

First -- you'll probably still be able to watch the content at a lower resolution if you really want to view it on your PC and you don't have an HDCP-capable monitor.

Second -- by FAR the biggest market for this is going to be set-top players and HDTVs, not people watching content on their computers.

Third -- complain to the people making LCD monitors for the last five years that haven't supported it, and to the content providers that are shoving this down everyone's throats.

4. buy your hardware and ignore the entire downloadable media.

Uh... what?
what are you asking?

Edit: After re:reading your post I think I'm looking at a different aspect of the rights management than you are speaking of. You don't seem to be talking about download and watch rights management, only insert and play type external media. Interesting to note that encrytion occurs each time. It makes sense as to why you'd do that I suppose. Do you know that they are applying the same rules to downloadable media?

Presumably you could use HDCP on any type of media, at least if it is supported at the OS level. Rights management issues are extraordinarily complicated. If you're talking about downloadable media that are essentially locked to the device you downloaded it on -- that's something separate from HDCP, even if they're using HDCP as part of their encryption system.
 

niggles

Senior member
Jan 10, 2002
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I need to read more, I thought I understood this better than I do. Thanks for the info.
 

erwos

Diamond Member
Apr 7, 2005
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I just wanted to add that the assertion you can just break any encryption you want is untrue. A really secure algorithm (not claiming HDCP is) is not going to be cracked with current technology.

Many thanks to Matthias for going to the plate for me - it astounds me how people make assumptions about technology sometimes...

-Erwos
 

niggles

Senior member
Jan 10, 2002
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Originally posted by: erwos
I just wanted to add that the assertion you can just break any encryption you want is untrue. A really secure algorithm (not claiming HDCP is) is not going to be cracked with current technology.
-Erwos

you need to look into this more. *anything* can be broken, the question is how much effort you want to put into it.

 

alpha88

Senior member
Dec 29, 2000
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Two things:

First, all these scary features only go into play if the content is marked with the DRM bit. Vista, HD-DVD, Blu-ray and all that crap don't require all media to display at low res through non HDCP connections, they just mandate that in order to meet the spec, hardware must support the DRM bit.

Hopefully, content producers can be convinced to produce discs which don't downgrade resolution on non HDCP connections. I for one, wont be purchasing discs that require an HDCP connection.

Second, there are chips which decode HDCP, and ways to ensure that they keep working when the player updates its list of blocked serial numbers. I'm pretty sure that a legal version could be made, or that shenanigans like this will help change the DCMA to allow certain devices. I think you can go a long way with the arguement that such devices don't strip copyprotection, which is illegal, but rather just allow you to connect your TV.
 

erwos

Diamond Member
Apr 7, 2005
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Originally posted by: niggles
you need to look into this more. *anything* can be broken, the question is how much effort you want to put into it.
First, that's untrue even in theory. You cannot break a cipher that uses one-time, truly-randomly-generated pads without having access to the pads. (And, if you've got access to the pads, well, that's the same as having the keys in any other algorithm. It's not quite breaking it.)

Second, that's untrue in practice. If an algorithm takes several lifetimes of the universes to crack with all the computing power in the universe, it is de facto uncrackable with today's technology. There are indeed situations where this is true, too. You can continue to argue with me about this, but I've actually got some background in crypto - do you?

I don't know why people don't seem to get this, but I'll repeat it again: the whole point of HDCP is to protect the entire path. If you're only protecting part of it, it's not only worthless, but an actual vulnerability. The HDCP consortium/alliance is not going to allow people to legally manufacture devices which are essentially HDCP crackers. This is not such a difficult thing to understand!

A challenge: describe to me a (legal) device that the HDCP consortium would allow that would allow for non-HDCP monitors to be used.

-Erwos
 

ND40oz

Golden Member
Jul 31, 2004
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Originally posted by: Matthias99
I can't wait to see how Microsoft makes the xbox 360 capable of playing back HDDVDs. From the tech specs I read, it only outputs an analogue signal and there are currently no DVI/HDMI cables for it. I don't think they're going to allow HDDVDs to be played at resolutions greater the 480p without a secure digital connection. But thats getting a little off topic.

It might help if they had an HD-DVD drive in it first. :p

Well, it'll definitely be external, I just wondering how their going to get past the HDCP restrictions with only analogue connections. I can't imagine they'll have another HDMI/DVI cord coming out of the drive to hookup to your TV, why wouldn't you just by a standalone?

link
 

MadAd

Senior member
Oct 1, 2000
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non-technical sidenote: a device made illegal in the US by whatever legislation may well be sold quite legally in the rest of the world- last time I checked you can order things from other countries (UK, Australia, Japan yaddaya). Isnt this a problem?
 

xtknight

Elite Member
Oct 15, 2004
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Originally posted by: erwos
First, that's untrue even in theory. You cannot break a cipher that uses one-time, truly-randomly-generated pads without having access to the pads. (And, if you've got access to the pads, well, that's the same as having the keys in any other algorithm. It's not quite breaking it.)

Nor would such a cipher ever be useful in even hypothetical scenarios. So every usable encryption can eventually be broken (even if it takes the sun to die first).

Regarding WMP DRM9: A Japanese hacker has repeatedly hacked the DRM9. As of this point in time, you can strip any DRM9 file of its encryption with two simple executable files. No, he didn't reverse engineer the (whole) algorithm, but he did find a way to get the decoded file anyway (in its completely digital original state). And that's the point.

That said, I still don't understand how HDCP is supposed to work. If every monitor is manufactured with a unique key, what prevents every DVIMAGIC from being manufactured with a unique key? Unfortunately they'd have quite a hard time blocking out all the pirated keys. All the hacking group needs is one working DVIMAGIC and they'd be distributing illegal movies all over the place just like before. IF that's true, how stupid of them to make us get all new devices to have this already-cracked HDCP in it. If it's not true, somebody enlighten me.
 

Matthias99

Diamond Member
Oct 7, 2003
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Originally posted by: alpha88
Second, there are chips which decode HDCP, and ways to ensure that they keep working when the player updates its list of blocked serial numbers.

The only real source for such 'chips' right now is the HDCP consortium. It's not the 'serial numbers' that are blocked, but the encryption keys that are used as part of the authentication step of the HDCP protocol itself. Unless you built a device that could change its keys (which would require inside knowledge of the protocol) -- and had a source of new, authenticated ones -- you're stuck.

I'm pretty sure that a legal version could be made, or that shenanigans like this will help change the DCMA to allow certain devices. I think you can go a long way with the arguement that such devices don't strip copyprotection, which is illegal, but rather just allow you to connect your TV.

I'm not sure what you mean, since any device like that would pretty much be doing nothing but stripping their copy protection scheme from the signal. Considering that the spec actually allows the content provider to choose whether to allow output to unprotected devices (possibly at reduced quality), there is little absolute 'need' for such a product. I strongly suspect that almost all content will be playable over component/VGA at 480p at the very minimum.

The legal problem here is that content providers are trying to protect their IP in ways that infringes on some things that have traditionally been covered under 'fair use' copyright law. In theory, it shouldn't be illegal for you to view your content at maximum quality on whatever display you want -- but allowing you to do so makes it trivially easy for people to make perfect, unprotected digital copies of said content.
 

Matthias99

Diamond Member
Oct 7, 2003
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Originally posted by: xtknight
Originally posted by: erwos
First, that's untrue even in theory. You cannot break a cipher that uses one-time, truly-randomly-generated pads without having access to the pads. (And, if you've got access to the pads, well, that's the same as having the keys in any other algorithm. It's not quite breaking it.)

Nor would such a cipher ever be useful in even hypothetical scenarios. So every usable encryption can eventually be broken. And most human engineers aren't as dumb as brute force cracks. (Well, some are. :p)

Such ciphers are extremely useful when absolute security is required and the pads can be pre-shared. I would suggest reading Neal Stephenson's 'Cryptonomicon', as it is both very entertaining and covers some of the topics around these types of codes.

Regarding WMP DRM9: A Japanese hacker has repeatedly hacked the DRM9. As of this point in time, you can strip any DRM9 file of its encryption with two simple executable files. No, he didn't reverse engineer the (whole) algorithm, but he did find a way to get the decoded file anyway (in its completely digital original state). And that's the point.

News to me. Source?

That said, I still don't understand how HDCP is supposed to work. If every monitor is manufactured with a unique key, what prevents every DVIMAGIC from being manufactured with a unique key?

Every model of device has its own key, not every single unique monitor out there. It's not a serial number, it's a device identifier.
 

xtknight

Elite Member
Oct 15, 2004
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Matthias99: I'm afraid it would be illegal for me to point you to the program but basically, there's key #1 that's openly available in every WM DRM file and you can get it by easy means (with a tool from the WM SDK). Then there's a second key that's returned by the DRM server. (Yes, you do need legal rights to the DRM file first, so it's not exactly a crack.) What this two-exe combo does is this. The first exe, a debug program, opens WMP in debugging mode and grabs this second key returned by the legal DRM server. Then the second exe takes the filename of the WM file and that second key, and begins the decoding process (that was reverse-engineered). So if you don't have rights to the file in the first place, you can't decode it. But if you do, you can get a perfect digitally-decoded version of the file. So for example if DRM put restrictions on play time (like you could only view said video for 5 minutes a day), now you can view it whenever you want.
 

Matthias99

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Oct 7, 2003
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Originally posted by: xtknight
Matthias99: I'm afraid it would be illegal for me to point you to the program but basically, there's key #1 that's openly available in every WM DRM file and you can get it by easy means (with a tool from the WM SDK). Then there's a second key that's returned by the DRM server. (Yes, you do need legal rights to the DRM file first, so it's not exactly a crack.) What this two-exe combo does is this. The first exe, a debug program, opens WMP in debugging mode and grabs this second key returned by the legal DRM server. Then the second exe takes the filename of the WM file and that second key, and begins the decoding process (that was reverse-engineered). So if you don't have rights to the file in the first place, you can't decode it. But if you do, you can get a perfect digitally-decoded version of the file. So for example if DRM put restrictions on play time (like you could only view said video for 5 minutes a day), now you can view it whenever you want.

lol... I wasn't looking for the program, just a description of it. :p

Interesting. Sounds like either they're transmitting or storing the second key in the clear at some point.

Also interesting that they were able to reverse-engineer the encoding/decoding (although I think they may be using a relatively standard encryption, so there may not have been much to actually do there).
 

xtknight

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Oct 15, 2004
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Some say it's just the consumer desperately trying to exercise their rights, and I agree. Who can tell me I can only listen to this audio file this many times, especially if I frickin' bought it? I must have subconciously agreed to one of their inane licensing agreements. I'm all for HDCP if it prevents pirates but in the end it's probably the innocent user that will end up having the restrictions (which are stupid in the first place IMO). Well, I am not all for it, since it requires me buying new hardware. No longer is it even possible for me to make a backup of a game I bought and own. I'm obsessive-compulsive, so I tend to make backups of everything remotely important to me. Did it stop game piracy? LOL, are you kidding? (Not ONE optical protection has not been bypassed as far as I know.)

And if they start injecting rootkits in to my system like Sony, hell no, that ain't happening.

As long as I can put a BD-ROM movie in my BD-player without getting some stupid message like 'your key is invalid' when I bought the movie, I'll be happy. That's not asking for much. LOL, the other day, I saw a 'theft deterrent' message on my VP930b monitor. To get it to go away I had to brute force the hard reset button combo (fortunately that was easy). Someone else also had this problem and posted it on a price/review site (they called ViewSonic about it and finally got the reset code). Jesus... (yes, I [my dad actually] legally bought the monitor from newegg.)

Edit: edited lots of times.
 

Matthias99

Diamond Member
Oct 7, 2003
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Originally posted by: xtknight
Some say it's just the consumer desperately trying to exercise their rights, and I agree. Who can tell me I can only listen to this audio file this many times, especially if I frickin' bought it? I must have subconciously agreed to one of their inane licensing agreements.

I'm not in favor of DRM like this, and in fact the market basically killed the DIVX DVD format that was competing with 'standard' DVDs when they first came out. It also used time-based DRM, such that you 'bought' movies for like $5, but could only watch them for a week unless you 'bought' them again.

Well, I am not all for it, since it requires me buying new hardware. No longer is it even possible for me to make a backup of a game I bought and own. I'm obsessive-compulsive, so I tend to make backups of everything remotely important to me.

Fortunately, a lot of companies have been moving away from this and relying more on keys or online registration to make sure you actually own a copy of the game. I suspect we'll see more and more things moving towards either online validation (like Steam) or subscription-based revenue models, since these are generally more effective at accomplishing the goal of having people actually buy the software.

Did it stop game piracy? LOL, are you kidding? (Not ONE optical protection has not been bypassed as far as I know.)

The biggest problem with these schemes is that they're trying to layer software-only protection on top of an inherently unsecure platform. The idea with HDCP is to have the protection built in at a much lower level, so that you can't bypass it by interposing a software layer at some point.

I'm all for HDCP if it prevents pirates but in the end it's probably the innocent user that will end up having the restrictions (which are stupid in the first place IMO).

The thing is -- the average 'innocent user' will never even know it's there. They'll have a Blu-Ray/HD-DVD set-top player and HDCP-compliant HDTV, plug them in via HDMI, and everything will just work fine.

Where things get messy is with HTPCs and people wanting to watch this content on their computers. That said, by the time Blu-Ray and HD-DVD are actually out in the US, most new LCD monitors are going to be supporting HDCP.
 

xtknight

Elite Member
Oct 15, 2004
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Yeah, the idea of Steam is actually cool and I like it. (Now they need to make Steam a stable program.)

(I edited my previous post for the 506th time and added in an anecdote about 'theft deterrent' on my monitor so take a look at that.)
 

Matthias99

Diamond Member
Oct 7, 2003
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Originally posted by: xtknight
Yeah, the idea of Steam is actually cool and I like it. (Now they need to make Steam a stable program.)

Hasn't given me any trouble, other than that downloading updates is sometimes kinda slow. Meh.

(I edited my previous post for the 506th time and added in an anecdote about 'theft deterrent' on my monitor so take a look at that.)

Yeah... uh... I have no idea what the hell that thing is. It was something in the monitor itself? :confused:
 

xtknight

Elite Member
Oct 15, 2004
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Originally posted by: Matthias99
Yeah... uh... I have no idea what the hell that thing is. It was something in the monitor itself? :confused:

Yup. Showed it translucently right on the screen, and locked every button. To turn the monitor off I had to unplug it. Then the message didn't appear until 5 minutes later.
 

her34

Senior member
Dec 4, 2004
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if nothing else there will be dvi strippers to remove hdcp. now keys can be blacklisted, but i'd like to see the day when a key from a popular hdtv model is compromised and worked into a dvi stripper.

will they blacklist the key and alienate all the consumers who bought that hdtv model? inquiring minds want to know...
 

Banzai042

Senior member
Jul 25, 2005
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If a company really wanted to make an HDCP stripper all they would need to do is buy the cheapest tv with HDMI inputs, open it up, find the HDCP decrypt chip, and reverse engineer it, not technically legal, but if they chose the right model, it would be impossible to blacklist because it would theoretically have the same key as a popular model, which would result in the scenario described by her34
 

Matthias99

Diamond Member
Oct 7, 2003
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Originally posted by: Banzai042
If a company really wanted to make an HDCP stripper all they would need to do is buy the cheapest tv with HDMI inputs, open it up, find the HDCP decrypt chip, and reverse engineer it, not technically legal, but if they chose the right model, it would be impossible to blacklist because it would theoretically have the same key as a popular model, which would result in the scenario described by her34

...except that doing what you described is EXTREMELY difficult if you don't already have a VERY good idea of how the thing works internally, and they have specifically designed the protocol to be hard to reverse-engineer.
 

Janooo

Golden Member
Aug 22, 2005
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Originally posted by: Banzai042
If a company really wanted to make an HDCP stripper all they would need to do is buy the cheapest tv with HDMI inputs, open it up, find the HDCP decrypt chip, and reverse engineer it, not technically legal, but if they chose the right model, it would be impossible to blacklist because it would theoretically have the same key as a popular model, which would result in the scenario described by her34


It's an option.
But millions of tv's are going to be sold. Millions of HDCP chips will have to be made as well. Some of them will go to HDCP - component converters. It's just a question of time.
 

hans007

Lifer
Feb 1, 2000
20,212
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i woudl assume eventually , that instead of building the dongle with a blacklisted ID, they could just clone the ID of say a particular tv that is already on the market.

it would be lik emac address cloning.
 

Janooo

Golden Member
Aug 22, 2005
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Originally posted by: Matthias99
...

The only real source for such 'chips' right now is the HDCP consortium. It's not the 'serial numbers' that are blocked, but the encryption keys that are used as part of the authentication step of the HDCP protocol itself. Unless you built a device that could change its keys (which would require inside knowledge of the protocol) -- and had a source of new, authenticated ones -- you're stuck.
...

The dongle HDCP chip will be updated the same way as any HDCP TV.
Unless HDCP chips are serialized there is no way they can be blacklisted. Even then the question is how they would know what to blacklist.