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New Technique For Making JPEG Images Copy-Evident
Gunkerty Jeb writes "The days of wondering whether those drunken sex party photos are indeed the Olsen Twins, or if they are just the Mary-Kate and Ashley's faces photo-shopped on the bodies of Lindsay Lohan and Amy Winehouse are OVER! A group of academic researchers at the University of Cambridge has developed a new technique for making JPEG images copy-evident, so that users can tell whether an image has been recompressed and copied."
If the image can't be re-encoded or re-scaled without the watermark becoming visible, then it probably can't be resized for viewing either. So the only images can can really make use of this 'tech' are the ones that are already shrunk to their smallest desirable viewing size. I'm not sure how much use this will really have.
identification of transcodes is very well-worn technology among MP3 users. Where people will take a 128kbps and transcode it to 320 and cause a small riot when people get upset getting a 320 that sounds like crap.
I imagine this is not really any different. Just look for the telltale squared loss and clipping, but in the image spectrum instead of the audio spectrum.
I work for the Department of Redundancy Department.
From the original paper: "The technique now needs to be extended to handle arbitrary photographs, not just uniform regions."
Nice try at getting fast karma from a first post, but that's not going to work. The screen shot will already be of the compressed image, and will still show signs of re-compressing it.
If you're really serious about putting Mary Kate and Ashley's head on Lindsay Lohan and Amy Winehouse's bodies, like it says in TFS, you'd use RAW. Then, you can compress everything together. Besides, if you upload that to photo sharing websites (especially Facebook) there's a high chance your picture would be recompressed, so it would have the compression artifacts whether it's been altered or not.
Fail.
Sigh, another pointless arms race brought on by businessman-academics selling snake-oil.
I wonder how long it will take to overcome the "message appears when a particular specific combination of recompression settings is chosen" anti-fraud-or-something technique. I mean, it's such a novel idea and there are so few alternative combinations of recompression settings.
The technique described in the article sounds like it would be defeated by applying a filter to the image before re-compressing it. It sounds like it is very dependent on having the encoder stumble over very specific bits in the image, and messing with those bits is likely to mess up the effect. Worse, if someone goes and finds your message (by encoding the image several times), it seems like it should be pretty easy to reverse the effect.
I read the internet for the articles.
"New Technique For Making Copy-Evident JPEG Images no longer Copy-Evident"
Seriously, I didnt sit in on the JPEG meetings or anything but it seems like this is a clever idea that could be so very easily circumvented. Recompress the picture, identify the regions exhibiting a "high frequency pattern" (which should be evident) and reverse the frequency of those pixels in the original file prior to recompressing.
See, now I can tell it's a Photoshop from some of the pixels and having seen quite a few Photoshops in my time.
I support the Slashcott and will not be reading or commenting from 2/10/14 to 2/17/14. Beta is steaming pile of dog shit
geez i hope they don't do this to movies. it will sabotage all those netflix dvds i "tivo to my harddrive" for "research purposes."
...just make sure you save as png, not jpeg.
So I downloaded their test image here: http://www.cl.cam.ac.uk/~abl26/copy-google.jpg that they claim gets a message on it when compressed by google proxy http://www.google.com/gwt/x/i?u=http%3A%2F%2Fwww.cl.cam.ac.uk/~abl26/copy-google.jpg&wsi=223e8e5df695e99c&ei=6ixQTebOCoPoxQW8rYlv&wsc=yq&whp=012e012f72be
But when I take the original and re-save it in Photoshop CS5 I don't see the void lettering. I reduced the JPEG quality and kept trying and at quality 1, the lowest setting I was starting to see a pattern, but no words appeared.
I'd say their idea is nice, but doomed to failure, not least they mention "If you can’t see the message in the recompressed image, make sure your browser is rendering the images without scaling or filtering." which would be the obvious source of attack on such a method should it actually work in practise.
-- oldthinkers unbellyfeel ingsoc
I see your point if it was compressed again using JPEG, but what if GIF or BMP, etc was used. Would that make a difference since they would compress the image using a different algorithm?
As usual this can be easily defeated by re-sampling or noise filtering. If you're targeting web media and have a high enough resolution source image then you have plenty of redundant pixels to play with to wipe out the watermark.
A better solution for authenticity verification would be digitally signed checksums.
Our algorithm works by adding a high-frequency pattern to the image with an amplitude carefully selected to cause maximum quantization error on recompression at a chosen target JPEG quality factor. The amplitude is modulated with a covert warning message, so that foreground message blocks experience maximum quantization error in the opposite direction to background message blocks. While the message is invisible in the marked original image, it becomes visible due to clipping in a recompressed copy,
I am becoming gerund, destroyer of verbs.
(keys desk intercom) Miss Jones, come in here! And bring your steganography pad!
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
I can see this if your concern is a pre-canned compression such as a specific proxy run by someone that doesn't care if the images it produce appear "marked."
If the goal is to prevent end-users from re-scaling the image in an arbitrary way, it's not going to be very useful.
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
This is why I ALWAYS do all of my drunken photo editing in .png!
GIF or BMP would be fine, since they are lossless. Whatever you get on the screen will end up exactly reproduced next time. The drawback is the compression ratio isn't nearly as good, so people tend to use JPEG for photorealistic images, which is why this technique is promoted to work with JPEGs.
Interesting technique, but clearly needs some work (since it only works on certain regions of some images).
"First they came for the slanderers and i said nothing."
"The technique now needs to be extended to handle arbitrary photographs, not just uniform regions."
Great, I've always wanted some way to tell if the blank wall in the background had been edited and replaced by another blank wall...
My job is image processing, and we are all well aware of the "quirks" of storing images as JPEG. Since it typically uses frequency information, converting to a BMP for a photo editor, and then converting back with some minor modifications introduces all sorts of artifacts into the JPEG coefficients upon recompression. These artifacts can be detected by a program looking for them, and I'm surprised such algorithms are not in use in existing software. And the detection would be able to ignore image resizing...
Of course, this kind of detection can be evaded by someone who understands the compression algorithms and knows how to work around it... but at least it could flag images modified by amateurs. After all, the TFA has the same goal, just it wants to make the "flag" be user-visible, not just rely on a program for detecting and flagging it.
As even the summary mentions, the technique applies to jpeg-compressed images.
Completely irrelevant tech. I've seen a few photoshops in my time, and I can tell by the pixels whether it's photoshopped or not....
Why, we'll make Rock Ridge think it was a chicken that got caught in a tractor's nuts!
I think you'll find that when it comes to Drunken Sex Party Photos, most of us who are going out of our way to look at them really don't care whether or not they have been edited.
---don't make me break out my red pen.
Knowing whether a photo or video has been digitally altered is important for images used as legal evidence. I would not be surprised to see makers of digital cameras and editing software embed a digital signature that can be used to detect alteration. Perhaps with software like Photoshop, it might even record what types of modification were done. There would be little reason to mistrust a photo that was merely rescaled, for example.
Keep in mind that some digital technology already embeds data to prevent counterfeiting.
They where not kidding about the specific quality settings. I tried it with the demo image and and The Gimp to reveal the message. I was only able to have it appear only remotely recognizable at 3 of the 101 quality setting
"The days of wondering whether those drunken sex party photos are indeed the Olsen Twins, or if they are just the Mary-Kate and Ashley's faces photo-shopped on the bodies of Lindsay Lohan and Amy Winehouse are OVER!"
You mean that poster next to my Olsen Twin poster is a fake? (Rushes off, and rips a poster off the wall).
I bet you can't guess which poster I removed!
Who would win this election: Andrew Weiner vs Andrew Weiner's weiner.
If you read the article, they are depending on the JPEG compression artifacts for the watermark display. Resizing should not cause this because you are deling with the uncompressed image data.
Resizing and then saving as a JPEG will result in re-compression and the watermark appearing. Saving as anything else bypasses this completely.
This is only useful when you know what conditions will be applied. The example they give near the end, uploading to youtube, will apply only as long as youtube does not change their settings. Then you have to change your thresholds and all of your protected videos in the wold are unprotected.
Our algorithm works by adding a high-frequency pattern to the image with an amplitude carefully selected to cause maximum quantization error on recompression at a chosen target JPEG quality factor.
The key here is JPEG quality factor. This only works on a specific quality factor. Just pick a different one. I just tried it using their example image. At some quality factors you can see somthing funny going on (spots on image). But, at any factor you would use to actually compress a photo (above 90) the image looks fine.
This could work for the bandwith-saving proxy mentioned in the article since they will have low quality factors. But what would be the point then? Mangling images when viewed on a cellphone?
I want my secretary to use a one-time pad for transcriptions.
Gif may be technically lossless, but only if you only want 256-colours. These days "lossless" means on 24-bit colour.
I-Swear-It-Is-Real.PNG
"In prison you just have to shut your eyes and take it. Here you have to shut your eyes and give it."
Through it all, at least Lindsay knows how to spell straits.
Well saving it in a lossless format is always going to be a way around any re-compressing artifacts. No "Print Screen" needed. Just load up the jpg in photoshop, do editing and then save as png.
Image sites that wish to deter fake images could force jpeg encoding, or make a jpeg available, maybe going as far as using something like tineye.com does to help find the original and flag the picture if they differ too much.
Olsen Twins, or if they are just the Mary-Kate and Ashley's faces photo-shopped on the bodies of Lindsay Lohan and Amy Winehouse
It would be more amusing to really transform the heads of Arnold Schwartenegger's and Martin Sheen's onto bodies Lindsay Lohan and Amy Winehouse.
Plastic surgeons in California can do that with Botox, can't they?
The cops would be too afraid to arrest a Arnold Schwartenegger headed Lindsay Lohoan. Poor Martin Sheen headed Amy Winehouse would hear from the traffic cops:
"I'm sorry Mr. Sheen, but are those two and a half double D's on your chest?"
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
jpeg also comes in lossless flavors
1. See interesting but slightly too small pic on web page
2. scroll wheel to zoom the page
3. IMAGE NO LONGER VIEWABLE BECAUSE ASSHATS ARE AFRAID YOU'LL COPY IT.
This thread is useless without pictures.
Nice try at getting fast karma from a first post, but that's not going to work. The screen shot will already be of the compressed image, and will still show signs of re-compressing it.
Nice try at getting fast karma from a first post correction, but I'm still going to correct you.
Anyone copying an image will have no problems. Copy-evident my ass, the file is 100% the same if I grab it and throw it in a torrent.
As for editing to remove watermarks / logos, the recompression will only show the message if your quality is below a certain threshold.
If you edit an image to remove the owner's information, and you see a "THIS IMAGE COPIED FROM SITE.COM" message, just save it at a higher quality.
Inserting the message will be a balance between visibility on the original (you want this low) and sensitivity to recompression (you want this high).
And if someone is insistent on using a low quality jpeg after editing an image you own, they can still easily defeat the scheme by doing an extremely slight blur on the entire image.
So the bottom line is that no, this isn't a copy-evident feature, it's an edit-evident feature, and one that is trivial to circumvent.
As even the summary mentions, the technique applies to jpeg-compressed images.
As even the post you replied to mentions, he grabbed a messaged-jpeg via print screen, and recompressed it via jpeg at "60" quality (I'm assuming that's photoshop's "60").
The screenshot provided is in two halves: The top half is the original uncompressed image, and the bottom half is the recomrpessed image. The file format png was chosen for the combined view specifically to avoid compressing the top half and compressing the bottom half a second time.
Actually, after playing with it a little bit, it becomes readily apparent that resizing (at least in Opera) affects this the exact same way that re-compressing the data as a jpeg does. As I run through the compression qualities in paint.net, I see the exact same patterns of compression artifacts in the images that I do when scrolling through zoom levels in my browser. Really, image scaling and compression are very similar problems, so this shouldn't surprise anyone.
This means two things. First, this technique currently only works at very specific jpeg compression levels (and on this particular image, it only works at qualities way lower than what I'd ever use for even a 10 minute cheesy photoshop hack job, which means it is probably just the default for MS Paint), so circumventing the protection is even easier than switching formats (just slide the quality bar over to the right when saving in any real image editing software). Second, and more importantly, even if they could make this technique universal, it would have the exact problem with resizing that GP mentioned.
Well, one of those palette entries can be transparent, so if you just stack enough GIF images on top of each other...
Okay... I keed...
Sort of...
Their sample image is here: http://www.cl.cam.ac.uk/~abl26/copy-background.jpg
Their sample image after recompressing is here: http://www.cl.cam.ac.uk/~abl26/copy-background-recomp.jpg
According to them, the sample recompressed image is saved "with particular quality settings".
So I opened the original image file in GIMP, went to save it as a JPEG, made sure the preview was turned on, and saw nothing.
Of course, this is because I save every jpeg at 1x1, floating point, 100 quality.
So I reduced the quality. After a while, the image appears. A change of 1% (from "82" to "83", for example) can render the message completely visible, and another change can render it completely invisible.
I did a low strength blur (imperceptible to my eyes) on the image, and went through the same experiment, and the message was rendered completely gone.
I suspect that same could be done by adding a small amount of noise, etc.
Yawn.
No joke, I've noticed a trend where more and more sites have these javascript or some other such crap to display the image. They begin with a insy tinsy image, when you click it shows enlargement but resolution is not great (and of course the right button and various commands are disabled). It is not that I will pirate images but it pains me to no end when I find a fantastic photo of i.e. Gina Lollobrigida (in one her beautiful dresses from "Beautiful But Dangerous" or "Fast and Sexy") and I want to save it because most likely that website has a limited lifespan! So far screen grabs (i.e. PrtScn or cmd-shift-3) still work.... but I wonder how much longer. Will it come a time when having to use a camera like what they did for "screen grabs" in the 20th century?
Regarding non-viewable images, if concerned of someone stealing an image, don't have images. Believe it our not, there are people with this kind of mentality. Like someone who takes a lot of photos at a convention or a fair but doesn't release the images out of fear someone will "steal" their photos. They argue that some of these photos may become pulitzer prize photos or incredible money shots. But hey, if they expect to get high monetary value photos at usual public events of various ordinary people, they are in the wrong place. Need to be with paparazzi types following Madonna or Britney Spears.
mfwright@batnet.com
If you know the watermark technique, then you can erase the original watermark and write a new unified watermark.
In fakes (including Tron 2), the main issue is that the lighting is never right.
In reality, the mouse cable is reflecting dark grey light at you. Each key on the keyboard is reflecting a mixture of black and and white at you. The screen is shining orange, green, blue, large masses of white, and grey on you.
If the person next to you has a blue dress, that blue is reflecting off you.
It's unholy ridiculously complicated and all they can do is "model" it and get close.
But it looks fake.
I was thinking for Tron 2, they should have had the young actor standing in for bridges (who had dots on his face) should have had white face makeup which would pick up the real room lighting and that could be used to adjust the lighting on the simulated young jeff face.
She was like chocolate when she drank... semi-sweet at first and then increasingly bitter.
I can tell from some of the pixels and from seeing a few shops in my time. What, are they borrowing an algorithm from 4chan?
Sometimes I doubt your commitment to Sparkle Motion.
It sounds like it would be relatively easy to detect this willful corruption and counter it... not a 100% inverse transformation, but it should be pretty damn easy to run a mock recompression, make note of the spots where it clips hard, and apply some kind of smoothing. Or, you know, I could smudge your evil pixels into oblivion.
It's an interesting piece of academia, but its reliance on what is effectively a glitch in the common JPEG algorithm means this technique will be trivially neutered by the very people it tries to affect. Heck, some guy will put up a single-serving website that uncripples your images, and that bastard will make a (small) mint on ad revenue.
-Billco, Fnarg.com
1. Fake Celebrity nude
2. Fake Watermark
3. Celebrity porn website with "real watermarked legit photos"
4. Profit
I've seen something very similar to this done to create a 65536-color GIF. Yes, the GIF palette is limited to 256 colors, but an animated GIF can have a different palette for each frame. With non-overlapping frames or careful use of transparency, you can get a true-color GIF.
"They redundantly repeated themselves over and over again incessantly without end ad infinitum" -- ibid.
Isn't the whole point of the format that it knocks back the color pallet to ~256 colors?
Actually, no. GIFs can contain multiple image blocks, each with its own palette. Ever seen a GIF with just under 16-bit color? Check this shit out.
FC Closer
an animated GIF can have a different palette for each frame
Well, that opens a whole new can of worms. I didn't know that, thanks!
How would one make such a GIF in GIMP, I wonder... brb 4chan...
At least based on the "VOID" test image they released, I did a bit of analysis and found that the pixels in the word "VOID" were only off by one compared to the rest of the image (whether light or dark pixels). This suggests that this technique (at least in its current form) may be defeated easily (while still recompressing as JPG) if you are willing to quantize each RGB value to either the nearest even or odd value (such that these small variations can be removed). While this reduces the color space quite a bit (it would basically be the equivalent of 21-bit RGB instead of 24-bit), for most photographic imagery, this will be virtually imperceptible. I await further results of this technique to see how it can be improved for photographs (since that does seem to be the primary intended use).
FC Closer
Adobe will have a tool to fix that on PS.
Bryan
Whoosh, my fellow AC, whoosh.
my guess is if you upsample the image by a large amount, then blur it at the upsampled size, then sownsample again you will strip the signal out. high frequency signals like that are going to be rather fragile because they have to hide in a complessed image and there isn't much excess data space to hide in with a compressed image
Snowden and Manning are heroes.
What you're commenting about is the reverse implant phenomenon. What it does is make a woman's breasts appear smaller when she has her clothes on.
"while democracy seeks equality in liberty, socialism seeks equality in restraint and servitude." de Tocqueville
Gif may be technically lossless, but only if you only want 256-colours. These days "lossless" means on 24-bit colour.
No 24 bit color gif you say?
I dream of a nation where a man is not judged by his skin color but by an number assigned by a credit rating agency.
Our algorithm works by adding a high-frequency pattern to the image with an amplitude carefully selected to cause maximum quantization error on recompression at a chosen target JPEG quality factor.
So...if I compress it as a TIF, a JPEG-2000, PNG, GIF, or BMP or else run a blur filter, resize, upsample, downsample, any image effects, or cropping 1 pixel off the top row/column (thereby ruining JPEG block alignment) then I can still edit images to my heart's content? Okay...so this is good for catching stupid people?
Also commonly referred to as a sports bra.
Then you just have the site enforce a size limit - jpeg compression is inherently lossy, so lossless jpeg images have very bad compression ratios.
Funny, I'm using Opera and can't make these images do this at all. Neither zooming nor Opera Turbo manage to make this watermark show up.
I see tongue-in-cheek commentary never gets to the point where you can digest it.... ;)
"while democracy seeks equality in liberty, socialism seeks equality in restraint and servitude." de Tocqueville
i think your page is slashdotted.
Wealth is the gift that keeps on giving.