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...or just use steganography. Steganography in videos can be made to be invisible to the naked eye, and extremely robust - even to video compression. It's also
by fredley 12y ago
...or just use steganography. Steganography in videos can be made to be invisible to the naked eye, and extremely robust - even to video compression. It's also difficult to detect, and even more difficult to remove/tamper with.
What the author of the article is proposing is actually a kind of steganography, albeit a rather crude one, and probably rather difficult to implement (since scene timings will be different for each episode, and you'll need to keep a separate log of exactly which timings correspond to each person you've distributed the file to), compared to running a video through a process that embeds a steganographically hidden id pattern at each keyframe.
- NoMoreNicksLeft 12y agoHow will that survive transcoding? What if you bump it down to 477p resolution?
- fredley 12y agoThere will be a limit to how much compression it can take, but some methods e.g. Echo Hiding are extremely compression resistant (I've implemented this over a phoneline - it works).
- mitchell_h 12y agoWouldn't a simple re-encode break any sort of stenography?
- fredley 12y agoNo. There are algorithms out there that can survive compression[1] by encoding statistically over an image instead of just bit manipulation. You can also embed data in the audio channel by alternating between two imperceptible echo kernels for 1/0[2]. This is extremely compression resistant. 1: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=4428921&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D4428921 http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumb... 2: http://www.slidefinder.net/a/audio_steganography_echo_data_hiding/jeff_england_audio_steganography/24367218 http://www.slidefinder.net/a/audio_steganography_echo_data_h...
- psk 12y agoSurely it would be possible to create encoding resistant stenography. Will the stenography be affected, sure, but it should be possible to create error-resistant stenography up to a certain point.
- dTal 12y agoStenography: encode information such that it is below the human detection threshold. Lossy compression: discard all sub-threshold information. Thus, in the general case it's fundamentally impossible. You can make a scheme that will survive certain known encoders and bitrates, but you can't make one that will survive all lossy compression.
- llimllib 12y agoOf course we have no idea if they used steganography or not, right? He bases the article on the idea that they have no tracking info except the watermark, but I don't see any evidence that they don't know more.
- fredley 12y agoTo be honest, when I heard that the files were protected with a watermark, I assumed that they actually meant a steganographic watermark. I thought that this tech had been adopted into the industry ages ago, I'm rather surprised if it isn't the case, given the arms-race between the media and illegal distribution.
- bru 12y agoSame here. I was really surprised. That's why I thought that my very simple idea warranted writing a post.
- rlx0x 12y agoYour initial assumption was correct, it is widely deployed in the industry, there are multiple vendors that provide fingerprinting technology that is orders of magnitude more advanced then what the article suggests. The visible fingerprint might just have been there to deter the clueless. In any case even with a fingerprint its hard to proof without a doubt, the individual who actually stole it.
- jjoonathan 12y agoThe visible fingerprint might also be there to prove intent or add circumvention charges in court. I don't think they need to prove that a certain individual stole it. The party which received the advanced copies likely had to take on liability, so HBO can go after them. Of course, that doesn't mean they won't turn around and lean on the actual culprit, but whether or not they catch someone HBO will have their due.
- anigbrowl 12y ago
- marquis 12y agoIt it were a full-screen steganograph it would need to be subtle as to not interfere with viewing. So could that be combatted by re-compressing with another codec?
- DanBC 12y ago> it would need to be subtle as to not interfere with viewing Pre-release screeners often have big ugly on-screen watermarks. Almost anything is better than a scrolling mid-screen line of text "PROPERTY OF STUDIO NAME DO NOT PIRATE THIS FILM".
- markbnj 12y agoCame in to say this. It's the obvious answer, and presumably the IP owners know about it even if the author of the article does not. It's also obvious that the author doesn't understand video encoding if he is proposing measuring millisecond differences in the length of specific scenes.
- URSpider94 12y agoThis. The minimum difference in scene length allowable would be a single frame.
- jjoonathan 12y agoDo you actually know that or are you speculating? I wouldn't be surprised if MP4 (or other video formats) provided a mechanism for tweaking the timing of a given frame. Of course, if you're using such a primitive watermark you might as well just add a note in the metadata...
- ianferrel 12y agoBut wouldn't it be trivial to notice that in the reencoding step and throw it away? "Huh, this frame is supposed to be delayed by 3ms. Ah, screw it, [checks 'force to 23.97 fps' button]."
- HelloNurse 12y agoYes, we know that. Video playback has physical constraints; a file format where image elements are sampled at irregular time intervals is obviously possible and useful for very "scientific" purposes like measuring when images are acquired and interpolating the raw data, but not reasonable for playing back on a screen with good compression and easy decompression.
- mappu 12y agoHuh? VC-1 in WMV and H.264 in MKV both support VFR. It's not uncommon for handheld video cameras or some anime sources.
- est 12y ago> and extremely robust - even to video compression. It's also difficult to detect, and even more difficult to remove/tamper with. Split & merge frame by frame, in random, from multiple video sources. Visually they will be the same, but steganography has a high chance of been broken.
- royjacobs 12y agoAny steganography solution on the market today that is worth its salt would actually be robust against this. The amount of different sources you would have to combine to protect against this is higher than you'd realistically be able to find. Disclaimer: I used to work at one of the leading companies in this field.
- est 12y agothe algorithm could tell exactly which sources are used in the final video? impressive!
- fluidcruft 12y agoAre you being sardonic? There are extremely obvious ways to do this particularly since they've got both space, color, sound and particularly time to play with. Unmixing signals isn't rocket science, especially if you've provided the signals that are getting mixed.
- Strilanc 12y agoThat's very interesting. I always assumed averaging (maybe with varying weights across frames and time), or applying a few rounds of other steganography, would degrade the encoded message into noise. Could you link to some papers? If you try to encode lots and lots of messages with different keys into the video, does it ruin the quality before ruining previous messages?
- royjacobs 12y agoI'm not sure in how much details I can go since a lot of this is behind patents and NDAs and whatnot, but just googling for "video watermarking" should already yield quite a few interesting details for you.
- edoloughlin 12y agoWhat the author of the article is proposing is actually a kind of steganography, albeit a rather crude one, and probably rather difficult to implement ...but easy to explain (and sell?) to the entertainment industry, who have shown themselves to be mostly technically illiterate. Some cynical, unscrupulous hacker could probably extract a lot of money from them for such a service...
- bru 12y agoAuthor here. That's my goal, but I don't have their email address so I simply wrote it down there.
- madaxe_again 12y agoWhile stego might be a route, blurring the watermark may not be enough to obscure the source. Given a known frame, they could blur the same portion of the same frame on all watermarked copies, and the one with a matching output is your culprit. Blurring loses information, but is more akin to a hash than a deletion, as it's a deterministic process. Edit: this sort of thing. http://dheera.net/projects/blur http://dheera.net/projects/blur
- peeters 12y agoIt's a deterministic process, but it still has inputs. You'd have to know those inputs or test for every possible set of inputs to whatever blurring method was used.
- spb 12y agoI imagine HBO knows every reviewer they gave a watermarked copy to.
- darkmighty 12y agoIt depends on the blurring method. If you do a gaussian blur, for example, you might be able to do a pretty good inverse blur by finding black frames and performing blind deconvolution. If I were at risk I'd use a nonlinear injective filter instead, to make sure information is lost (linear filtering is not only deterministic but perfectly without noise and no frequency response nulls).
- sorokod 12y agoSteganography (which may or may not have been used) wouldn't have any effect whatsoever on the number of downloads
- jamesrom 12y agoI don't see anyone anywhere claim that it would. It would only aid in tracing the source of the leak.
- sorokod 12y agoTrue - and then what? The leaked episodes may have been stolen or can be claimed to have been stolen. Anyway, the horses have bolted and the damage is done.
- cpeterso 12y agoYes, but the leaker would be blacklisted from all future HBO (and possibly partner) pre-release materials.
- tbabb 12y agoAnd probably sued into oblivion.
- sorokod 12y agoDo you know for a fact that the leaker is the same person (organisation?) that has received the official HBO material? Maybe it is more like this: http://www.ibtimes.co.uk/expendables-3-online-leak-two-arrested-over-damaging-pre-release-movie-piracy-1476498 http://www.ibtimes.co.uk/expendables-3-online-leak-two-arres...
- c22 12y agoMaybe so, but HBO isn't obligated to prove guilt beyond reasonable doubt. Arguably if someone can't keep the screener secured from internet thieves they're still not a trustworthy guardian of the content.
- DrJokepu 12y agoThis might be a very naive suggestion (I know nothing about the subject) but couldn't you just take two copies, XOR them and blank out the difference to defeat such signatures?
- darkmighty 12y agoWe're talking about images, so if you take the pixels for example they're just {0,...,255}^n, integers. You can if you have the original file, but then what's the point? Otherwise, take image a=original+f1, image b=original+f2. Then if you e.g. average them you still have c=original+f1/2+f2/2 -- so both signatures are kept (theoretically if either you have a large number of sources you could average the signals out of existence, or perhaps the system isn't robust and can't detect multiple sigs). This assumes the introduced signatures are indistinguishable from the source (quite reasonable).
- allemagne 12y agoEven if that worked (maybe it does, I don't know) you'd still have the very major obstacle of getting two potential leakers (from presumably separate publications) to find each other and collude without getting caught.
- contravariant 12y agoI think that could be avoided by making sure that large parts of the signatures overlap. There's probably some scheme to be able to recover which copies were used to make the leaked copy (up to some finite number of copies, but it quickly becomes impractical to get enough copies).
- MichaelGG 12y agoOver 4 separate files, depending on how they encode the IDs, you might still find out who the leakers are. They might share some bits and not others. The studio can take its time if it has a serious leaking issue.
- tbabb 12y agoI will say that steganography is definitely in use already, at least on feature films. (It's particularly easy in animation, where literally anything can be changed seamlessly). A film pirated from a theater (even by a camera pointing at a screen) can easily be traced to the exact theater and showing of the movie, and IR cameras in the theater permit authorities to identify the exact individual with the camera. In short, don't try to film a movie in a theater; they will find you.
- azakai 12y agoYes. The author of the article is barging through an open door: It's very likely that those Game of Thrones episodes had individual hidden watermarking, and that using those they can tell exactly who leaked it. The author jumped to the conclusion that those don't exist, apparently because they aren't visible (but that's the point!) and that there is a visible watermark which the author apparently assumed was the only one (but it almost certainly isn't).