DRM technicalities

[chewbacalips]

I was considering DRM encryption lately and thought I'd ask how it works, in the technical sense. I understand that media files that are encrypted with DRM require a license/key to decode/unlock the encryption. But how does the encryption itself work, and why has it become impossible for people to remove the encryption WITHOUT having a license/key?

To better articulate my question, let me use an analogy. To my understanding (I'm not a techie, so I could be wrong here), digital media files are much like a book. Whereas a book is comprised of its pages, a digital media file is comprised of streams-of-code. Thus, removing streams-of-code would be like removing pages in a book. Furthermore, randomizing the streams of code would be like randomizing the pages within a book.

If this is correct (which might not be the case), then I can personally think of several ways that DRM encryption and decryption would work. I'm hoping you guys could confirm whether any of these are correct or if you know the true way that DRM works:

1. DRM would cause the 'pages of the book' (i.e., streams-of-code within the media file) to be scrambled into random order. The DRM license/key would be the necessary tool for putting the 'pages' back in their proper order.

2. DRM would create some kind of lock so that you can't 'open the book.' I remember a lot of girls had diaries in elementary school with locks on them, the key to which would be dangling on a necklace. The DRM license/key would simply open the lock.

3. DRM encryption would steal a chunk of 'pages' from the 'book.' Imagine finding a book with a bulk of random pages missing. You could make no sense of it. The DRM license/key would then insert the 'pages' back in so that you can read it. (Although I think this is a possibility, I'd consider this the least likely answer to my question, because this would mean that the encrypted files are missing data, and would thus have a much smaller file-size. But that's not the case. When you unlock an encrypted file, I believe the file-size remains the same, indicating that all of the data was there the whole time. Furthermore, this scenario would resemble a torrent download, where you are constantly downloading chunks of data at a time until you acquire all of the chunks to complete the file. Even when your file is, say, 50% completed, you can still access that 50%. Thus, it seems to me that option 3 is not the method employed by DRM.)

4. The fourth option I could think of would be some kind of combination of the above 3.

Any thoughts on this issue? Is my understanding correct? Too simplistic maybe, etc?

[Ghitulescu]

Your question is like Man (as the whole mankind)) is sick. Is is possible to treat him/her/it without killing him/her/it?
DRM is a generic term like the term man. A Chinese, an African, A Spaniard, a Swede, all are men but different.

There are to my knowledge some 200'000 technical papers about DRM (which are public), I'm not including here articles in magazines, newspapers, online articles, forum topics and the like. Are you willing to read all of them? If not, then narrow a bit, say SafeDisk 2 (still large), say SafeDisk 2.5 (still large but ok) ....Revise your ideas, get a starting point, then come back.

[Ajax_Undone]

Mostly somewhat maybe never...

As Ghitulescu pointed out the library of DRM is much larger then the umbrella term used. For instance I buy GTA 4 it has SECUROM 7 on it. The drm in this case is a CD/DVD validation built into the Game media and the main executable game file. If set off it will prevent me from running the game. So rips iso's etc are worthless unless properly emulated or a no-cd/dvd patch is made by a third party hacker with skill. The there is the DRM used on modern movie media known to the world as aacs (http://en.wikipedia.org/wiki/AACS_encryption_key_controversy) uses an encryption which uses the key system you proposed. Only it used two keys a Parent and a Child key one would unlock the other for access in blessed players.

SO to some it up you need to be a little more specific as to what you ask. One question what is the reason for your inquiry? If you don't mind me asking...

[J_Darnley]

DRM on media is usually encryption and you either need to communicate with a server to get the key or it is buried in software or hardware code and fiercely protected by the owners. In this category you have: DVD, Bluray, iTunes, protected WMA, etc.

DRM on media can also be a system of flags or instructions to prevent the user from doing things. In this category you have: PDFs which prevent the use of a screen reader (IIRC); Javascript on webapges which prevent right-clicks, selecting text, etc.

DRM on software is much more varied but does not usually involve encrypting the whole thing. Various disc checking methods, hardware dongles (very old school) and now communication with online servers.

Now as for your bolded question, in short, you need to know the algorithm if you want to try to break it with brute-force. For a good encryption method this would take a very long time. For a weak method, it is probably not necessary. Someone will probably find a way to exploit the weakness.

[chewbacalips]

I didn't realize that DRM could be applied in so many ways, and thus requires a narrowing of terms when in discussion. But being a non-techie (all I know is commercial electronics, no programming or anything of the sort), there's limited info I can give you. I'll tell you the full story as to why I'm inquiring about it, but I usually hate doing this (I've explained my scenario dozens of times over the years) because people always give me stupid answers that are irrelevant to the question.

Short version of the story: I have 2 WMA files from 2005 that are encrypted. The keys are nowhere to be found, and even if they were, they'd be long expired by now.

Long version of the story: In 2008, I became a fan of a particular band. I did some Google searching to look for some more of their music. Using the "cache" function on Google, I found an old and expired page from a large website (I was only able to access the page with Google's "cache" function). The site was www.7digital.com, where they distribute digital audio, much like iTunes does. Anyway, the page I found was from 2005 (bear in mind, when I was viewing this page, the year was 2008). As it turns out, 7digital held a promotion for this band, in which they provided downloads to 2 songs from the group for FREE (they often offered select songs for free). At this point in time (2005), the band had recently signed to EMI and would not release their FIRST album until 2006. Thus, these 2 songs pre-dated their debut album. In the promotion, 7digital stated that these 2 songs would NOT be released on the upcoming debut album in 2006. Sure enough, they weren't on the album. I happen to own every CD, DVD, vinyl, promo and single from the group, including some demo items, and the 2 songs are nowhere to be found. I was able to download the 2 songs directly from the cached page, thankfully. However, I also found a little note on the page indicating that these songs would expire on a certain date (sometime within 2005). After downloading them, sure enough, the DRM did its job. I am in possession of 2 unreleased songs by a loved band, yet I will never be able to hear them.

I've looked and looked and looked into DRM hacking, only to find that you cannot remove DRM encryption from the WMA file without having an active license. It would seem pointless to require a DRM-stripper if you already have a license, unless of course you consider cases like mine where the file is playable for only a short duration of time. Of course there are other limitations that DRM imposes on an individual, which arouses the necessity for a DRM-stripper.

So, that's my problem: in 2008 I've acquired 2 WMA files from 2005 which are locked securely forever thanks to DRM. I can never enjoy the WMA songs because they were never made available outside of those 2 files.

So please, don't ask me why I don't just "use napster to download playable versions," or why I don't just "buy the CD" like some morons on various websites have done. The frustration I experience from such stupid responses will nearly produce a stroke.

[CruNcher]

I was able to download the 2 songs directly from the cached page, thankfully. However, I also found a little note on the page indicating that these songs would expire on a certain date (sometime within 2005). After downloading them, sure enough, the DRM did its job. I am in possession of 2 unreleased songs by a loved band, yet I will never be able to hear them.

As soon as the Label decides to release them you will, so just contact the Label who has the Rights on the two Songs and ask them what happened to those maybe the Group you talking about didn't want them to be released for some reason or the Label pulled them of after the Group signed with EMI, though that's the problem with commercial publication and studio Groups they dont have the Rights on mostly anything just puppets, sign here and get rich the devil said ;)
See what's happening with Michael Jackson currently only a dead Singer is a good Singer, so as soon as the whole Group you talking about died those 2 songs will be released for sure ;)
DRM is also to stay with us and it will become more optimized in the future there is a lot of Research going on to make it more strength and also to widen it out not just to the files itself but to the whole Infrastructure beneath those including transfer routes.

[Ghitulescu]

Well, should you have told about DRMed WMA would have been simpler to us to give you the right advice.
You can:
- wait until Doomsday for EMI to release songs that pre-dated its contract (in simpler words: EMI has no contractual responsibility for what was "before", yet the band cannot release them without EMI accept since they have, you said, exclusive contract).
- or google for a DRM cracker for WMA (I can't help you here, I'm not into MP3 nor WMA or the like, any type of lossy compression actually). FairUse comes to my mind. Anyway there's a site called, surprise, surprise undrm.info.

It seems that even here you couldn't find the answer -> http://forums.afterdawn.com/t.cfm/f-37/drm_killer_for_wma_audio-835139/

[CruNcher]

- wait until Doomsday for EMI to release songs that pre-dated its contract (in simpler words: EMI has no contractual responsibility for what was "before", yet the band cannot release them without EMI accept since they have, you said, exclusive contract).

Hehe that and they actually don't have any rights todo so even if they would like those 2 songs to be released they would need an agreement with the previous Label that produced those so actually buy the 2 songs from the Previous Label and then release them and depending on how successful the group is the price will be ;)
So in the end if your current Label don't see a use or a potential market for those 2 songs you as an artist would need to purchase them back from your Previous Label :D

The Machine is Evil and in the last years it's gonna more out of control http://www.linamorgana.com/site/linamorgana/files/videos/4.flv

and it goes on http://www.youtube.com/watch?v=1sUKeQLjDEI