Blurring Images Not So Secure 166
An anonymous reader writes "Dheera Venkatraman explains in a webpage how an attacker might be able to extract personal information such as check or credit card numbers, from images blurred with a mosaic effect, potentially exposing the data behind hundreds of images of blurred checks found online, and provides a ficticious example.
While much needs to be developed to apply such an algorithm to real photographic images, he offers a simple, yet obvious solution: cover up the sensitive information, don't blur it."
Japanese porn (Score:5, Funny)
Re:Japanese porn (Score:5, Informative)
Now cue about 50 posts talkng about the "CSI Photoshop enhance plugin".
Re:Japanese porn (Score:4, Funny)
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Speaking of Slashdot memes, do GNAA trolls still show up? I haven't browsed below +4 in a year, so I'm not entirely sure.
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I always thought porn was for hiding Soviet spy messages. I suppose pictures could hide horse porn with steganography.
Re:Japanese porn (Score:5, Funny)
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Re:Japanese porn (Score:5, Funny)
Only if the number of possible cunts is fixed and known.
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Somehow, I feel like I'm not reading Slashdot. Did the channel get changed over to MTV's New Year's Countdown [youtube.com] (language NSFW)?
I hereby dub Tablizer the John Cleese of Slashdot. I've never seen anyone use that word here before (John Cleese said "fuck" during his eulogy of Graham Chapman at the televised funeral, and allegedly was the first to use the f-bomb on TV, or something like that).
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No really, I really did hook up with a Phillipino girl, but that was before I declared CS as my major.
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I'll just be careful to never tell that story so as to not screw it up again. Got lots more, though. Being an RA on a freshman floor sure did diversify the available and willing gene pool. Then I majored in CS and that pool evaporated.
and please... (Score:5, Funny)
And please, when you cover the information with black bars, use Adobe Acrobat. (this solution brought to you by the CIA)
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Sqinting Works (Score:5, Funny)
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Re:Sqinting Works (Score:4, Funny)
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-N
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-N
Re:Sqinting Works (Score:5, Funny)
Re:Squinting Works (Score:2, Funny)
old news - I see this on TV every day. (Score:5, Funny)
Re:old news - I see this on TV every day. (Score:5, Funny)
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Whichis why it uses the authentic photpenhance sound effect as the image appears in rows, like dot matrix printer. Us imaging professionals see that every day.
The weird thing is that they must have a whole staff of highly qualified computer geeks who do their effects who could tell them this was bullshit.
Re:old news - I see this on TV every day. (Score:4, Interesting)
You need to realize that CSI is science fiction masquerading as a cop show. Their impossible tricks with image processsing and the like are the show's equivalent of FTL travel. But despite having miraculous technology, they actually get the method and attidudes of science right, at least on the original series. They look at the evidence, and struggle to overcome their prejudices regarding what they would like to be true. Sometimes they follow false trails, and have to accomodate new facts by discarding the theory they've built up so far.
Gil Grissom may be the only character in TV history who actually behaves more-or-less like a real scientist.
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I suppose that's one way to look at it. For me, I gave up after the first season. The "false trails" thing just became a cliche; you KNOW that it's never the one or how who it seems to be first; that's always a red herring. And the complete unreality of the CSI geeks going around
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You obviously haven't watched it this season. The number of cases that roll over from one episode to the next has greatly increased this season. As a matter of fact, the one running plot (the miniature killer) that spanned, I believe, more than 4 or 5 episodes, which they neatly tied up a couple weeks ago, appears to have resurfaced in the season opener.
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Relief. Shadows. Focus of attention.
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Of course there is a problem with people taking it to extremes and wanting perfect photographic evidence, but overall I think Juries have been too lenient on what evidence they'll convict on.
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Impossible! (Score:2, Insightful)
Re:Impossible! (Score:5, Informative)
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So, if you blurred it, you must have edited the photo. So in no way does a photoshopped photo prove you won a million dollars. Completely blanking out (with pure white, pure black, a texture, etc) the image proves just as much as the blur. WTF is the point? By contrast, PDFs and DOC files requires un
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So, if you blurred it, you must have edited the photo. So in no way does a photoshopped photo prove you won a million dollars.
Nor does coming over to your house to show you the actual million dollar check prove that I won it either. For all you know, I might have printed that one myself on my new color laser printer. Of course, I could deposit it and show you my online bank balance. But maybe I've setup some kind of strange proxy which does a man-in-the-middle with the bank and replaces a deposit for $100.00 with one for $1000000.00 instead. Or I could take you with me to the bank and deposit it with the teller. But maybe th
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100 120 140
110 130 150
120 140 160
becomes
130 130 130
130 130 130
130 130 130
and there's no information here that can be recovered about the distribution. The only thing that happened here was that he conviently choose a block size and low-information data which essentially mapped 10 possible values (images of 0-9) to 256 shades of gray. Obviously, you can now find that there's one shade per number. In a photo t
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Dude was effectively talking about a dictionary attack on the blurred information; he was treating it as a one-way hash and was at no time attempting to decrypt the information. What he was doing was reencrypting (reblurring) every possible combination possible on the image in question and seeing which one was closest. For a mosaic effect like the one he described (which is used quite frequently), it seems to be pretty effective.
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Unless there are many frames? (Score:2)
an algorithm to "un-blur" a blurred image is a total waste of time
Maybe for a single image, but how about blurred or pixelated informants or (increasingly) logos on TV, with many closely correlated frames?
how about a big DUH..... (Score:3, Funny)
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He was parodying the massive level of ignorance this thread is displaying about Photoshop, and image processing in general.
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Blurring CAN be secure (Score:1)
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RTFA (Score:5, Informative)
The whole point of the article is that blurring and pixelating beyond recognition isn't enough. You don't need to see the original numbers, you just have to find numbers that blur to a similar blob. It's a dictionary attack with blur as a hash function.
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Please, RTFA. If you know these are numbers and the font (as on a credit card) that means you only have to get 10 levels of grey to have an excellent chance of working each digit out. You can't "see" it, but the information is there. Just use the eyedropper to select one colour, then paint over it.
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And cover it correctly... (Score:4, Interesting)
People who do not understand the technology they are working with should not have this kind of release authority. And that's the hard part--the higher up you are in the food chain, the less likely you are to understand the new tools your organization is working with.
There are very few users in government who could not do their jobs just fine using Windows 3.11, WordStar 3.x and an e-mail client on a fast but simple machine.
Slaved as the government is to Microsoft's development cycle, however, the government will always be at the cutting edge of compromised.
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I thought of the PDF thing too when I read the article!
Yeah, that's decidedly the exception to this rule.
Un-blurring photos (Score:2, Interesting)
While I acknowledge knowning little about different blurring algorithms could someone enlight a bit how much of "unblurring" can be done? I realize there are some "sharpen" filters in Photoshop and Gimp but AFAIK they all seem to be based on highlighting edges or something like that.
As in the TFA, the Bill Gates picture has a small part of it blurred (his face). Could it be possible to calcute all the possible variations that give the same bitmap as the original when filtered with gaussian blur? What I
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It's called Deconvolution (Score:2)
In short: "Blurring", as most image processing software does it is a convolution (i.e. a multiplication in Fourier-Space) of the original image with a Gaussian kernel. Since the resulting image is real but the multiplication takes place in the full complex Fourie
Summary of technique (Score:5, Insightful)
Interestingly enough, while he points out that most financial account numbers contain a degree of error detection and correction, he chooses to use that to reduce the match set, rather than the candidate set. I suppose this would matter if you wanted to prove a hypothesis (if the best match yields a valid number, you have a p=[valid/total]), but if you just want to steal someone's account info, you'd do better to reduce your processing time and just try the best few results in order.
You can actually go one step further with wavelets (Score:5, Insightful)
In contrast, wavelet based scaling can actually reconstruct phenomenal amounts of detail from a degraded image. For digital TV applications where you have DVDs or standard definition content displayed on a high-definition fixed-resolution display, wavelet-based scaling can actually make real details re-emerge where they weren't there before. The bottom line explanation is understanding and interpreting the influence of adjacent pixels with a minimum of error as the article's author demonstrates (although, as the parent post explains, he's going about it in a convoluted way). I've actually seen the preliminary results that some engineers had shown me that makes it look like something a government agency would use to enhance satellite or surveillance camera images. It makes DVDs look almost exactly like HD-DVD or Blu-Ray HD content. In fact, I expressed my concern that this scaling method could be used on digital TVs to actually "unmask" blurred or blocked faces on TV shows and introduce liability issues.
Nevertheless, it is possible to reconstruct a LOT of detail from blocked out or blurred faces or pretty much any content. Doing it in real time on HD resolution displays is a different matter altogether as it requires enormous computing power. But it is coming in the next 3-5 years. If you're really interesting in blocking out content on digital photos, use a solid black color over the part you don't want recognized.
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which can give the subjective impression of improving detail, but only because that is what our brains expect to see in a sharp image.
Does anyone have a l
Re:You can actually go one step further with wavel (Score:2)
> solid black color over the part you don't want recognized.
No need for black. Just replace the part you don't want recognized with something else rather than blurring it (or better yet replace it and then blur it. Let them waste their computing power).
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Multiple passes? (Score:2)
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MaxEnt (Score:5, Informative)
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I did read the article, and I wanted to point out that what they are doing is not entirely new. Their approach is somewhat different than what you usually see, but the idea is basically the same.
I also know that convolution isn't always reversible, but in many cases it is. I've made professional use of deconvolution to cancel motion blur in a well-defined system. In less defined systems you need to use stuff like MaxEnt, but it also assumes that there is some unknown, well-defined convolving function.
maximum entropy (Score:5, Informative)
In the real world, data is imperfect and noisy, so the article is thus far correct. What is not correct is simply to pick the data with the nearest match, because it's a best match to the noise also. Maximum entropy is one algorithm which gives you a probabilistic answer, i.e. "the chances that this particular combination is the right one is [whatever] percent". You then pick the most likely one. Astronomers use this technique all the time for removing the blur and diffraction on their images. I personally use it regularly for nuclear spectroscopy, and it's absolutely solid if you use it carefully.
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I personally use it regularly for nuclear spectroscopy
Yeah, who doesn't?
Hand Written Checks (Score:2, Funny)
Fragment-based image completion/reconstruction (Score:2, Informative)
There's quite a few more impressive papers on his page, for those interested in graphics.
PDF Files (Score:2)
If you read it on screen or printed it out, it worked as they expected. But when you selected the text and copy and pasted it somewhere else, you could read every bit, including the names and details they thought were obscured.
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Not a company, 'The Company'. They were declassified CIA documents if I remember rightly.
Dont waste time bluring stuff, erase it. (Score:2)
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Mathematically speaking, a blurred image... (Score:2)
Now perform a simple blur by averaging each pixel withh its neighbors (padding with zero at edges):
Suppose we lose the original. Note that we have still have 6 values and we know the equation that generated each one. So we have 6 equations in 6 unknowns, and we can solve. (In real life blurs are more complex, but in practice they are still linear, including blur fr
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"But, really..." (Score:4, Insightful)
So yes, I used an image against itself and designed it to work here. But the algorithem can surely be improved to work on real stuff. I don't have the time nor desire to improve this any further, though, because I'm not the one after your information.
Yeah, like: surely someone else can make it work - I've only described a fantasy in an article that'll work only under fabricated examples and circumstances and I don't want to put myself in a position of proving it unworkable in general use.
This would only work if you know the exact setting (Score:2)
You'll find it here:
http://www.dslreports.com/r0/download/800075~433b 0 c31ec1520970b77229393b7d713/vonage.png [dslreports.com]
Now, unless you know what mosaic settings I used, I don't see anyone cracking these numbers anytime soon. I think this sounds good in theory, but no good in practice unless everyone is using the exact same software to do the mosaic modification.
Not blur, pixelation (Score:2)
First, this isn't blur, it's pixelation, with big pixels. That's not the same as blur. True blur, like Gaussian blur in Photoshop, doesn't actually destroy that much information. After Gaussian blurring, each pixel has a unique value, but it's a linear combination of values from nearby pixels. There's almost as much information as before blurring; the only true losses are from rounding. That's a reversible process. [nist.gov]
Pixelation, though, substantially reduces the amount of information in the image. Bef
Blur is sketchy. (Score:2)
I agree that blur is not a great idea, but "black bar" is tacky. Either get the area to match the surrounding area, via copy-and-paste (and then blur or something), or match the color and paint over.
If those techniques make it look obvious, I've used Noise and Scatter in the past. Since Scatter is presumably
Just use black (Score:2)
I don't care what algorithm you're using, you can't reverse a black paint stroke to discover what is underneath, those pixels are gone. (short of using code that exploits the multi-layers aspect of some image formats - but paint is not susceptable to this
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That isn't 'lazy programmers'. That's people trying to up their search engine rank without bothering their customers with a ton of pointless text.
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You're new here, aren't you? (Score:5, Funny)
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http://digg.com/offbeat_news/How_much_was_this_ch
Google image search will give you tons more examples... not just of checks but people block all kinds of things. Scanned bills, paystubs, etc. and mosaic parts of images.