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Detecting Faked Photographs Gets Easier
nusratt writes "Some years ago, an issue of 'Whole Earth' had a convincing cover-photo of a flying saucer cruising low over downtown San Francisco in broad daylight. The accompanying feature article proclaimed that photographs can no longer be trusted as evidence of anything, because of the ease of doctoring images digitally and undetectably. Now, Dartmouth Professor Hany Farid and graduate student Alin Popescu 'have developed a mathematical technique to tell the difference between a "real" image and one that's been fiddled with.' Farid says, 'as more authentication tools are developed it will become increasingly more difficult to create convincing digital forgeries'." There's also an NYT story.
While an equation to make sure that a photo is not forged is all well and good, it is self deafeating. Just like simple encryption, which is good for people with simple problems, exploring the equation will yield a way to fool it. If you have someone who truely wants to forge a photo, they probably could still defeat the check.
Farid and his students have built a statistical model that captures the mathematical regularities inherent in natural images.
I wonder if they've considered the potential applications in image compression?
While this might not be a problem for gross manipulations (the faked John Kerry/Jane Fonda photo being a recent example) I can imagine a class of images where subtle manipulations caused great effects and were not readily distinguishable from compression artifacts.
cheap labor conservatives - they want to keep you hungry enough to be thankful for minimum wage.
The article says the research is founded by the Department of Homeland Security. That means that despite the many useful possible aspects of this technology, it will probably never see the light of day. If the DHS is going to be using this technology to identify faked photos, it would be greatly in their interest for the full algorithm and its implementations to not be made available to the public-- since after all if people know what the DHS is using to determine faked photos, they can target the algorithm.
Now that I have written that, looking around, it appears I am actually wrong. If you look at Mr. Farid's personal page, it appears he will be publically presenting a paper covering the fakeness-detection algorithm. I hope the full algorithm will be presented to the academic community.
People making fakes of UFOs and breasts on the Olsen twins will discover new techniques to overcome the detection. It will always continue in a spammer/spam-filter fashion. I'm sure that we'll soon see tools to automatically take the mathematical principles into account and automatically correct fakes that can be detected.
But hey, I'm pretty sure this one pic of the Olsen twins I got from Kazaa is real anyway.
put the what in the where?
So if it detects digitally altered images, why can't we just 1) Alter the image to our heart's content 2) Print it on a high quality printer ($500- $2K at CDW) 3) Scan it back in with a nice scanner
"The object of war is not to die for your country, but to make the other bastard die for his." - Patton
I gotta say, while the first half of your comment was certainly insightful, that was one of the most blatant attempts to force your pet project into an unrelated comment I've ever seen!
You, sir, have balls!
Farid and his students have built a statistical model that captures the mathematical regularities inherent in natural images. Because these statistics fundamentally change when images are altered, the model can be used to detect digital tampering.
That's pretty much all the detail on the method to detect image altering. Seems reasonable, but:
1) How many real photos deviate how far from the statistical "norm" (i.e., how likely are false positives when checking for alteration?)
2) How long before there are tools that can inject the proper (expected) statistical characteristics into a faked image?
These are not addressed in the article. Anyone have more info?
everything in moderation
My first thought on the article was the same. The mathematical tests to determine fake photos will have value only until the fake photo industry builds the tests into their software. For that matter, I suspect that the main use of the Hany Falid method will be to make your fake photos even more realistic.
The most interesting line in the article was:
One could read into these lines that the ability to fake photographs was great until anyone could do it. Now that we know how easy it is to fake photographs, we no longer implicitly trust messages...but we will trust mathematically authenticated fake photographs because math is infallable.
One could read into these lines that the ability to fake photographs was great until anyone could do it. Now that we know how easy it is to fake photographs, we no longer implicitly trust messages...but we will trust mathematically authenticated fake photographs because math is infallable.
Or you could read into them that when it was rare and difficult to fake photographys, most of the photographs you saw were genuine, so you could place a decent amount of trust in what you were seeing. Now that faking photos is easy and commonplace, you can no longer place much trust in photos. With mathematically verified photos, you can place more (though not complete) trust back in the photo. It isn't foolproof but the level of assurance is significantly higher.
"The legitimate powers of government extend only to such acts as are injurious to others." Thomas Jefferson.
To me this strikes me as the same sort of "solution" as DRM is, sure it stops Joe Six-Pack from putting Britney Spears' head onto a porn stars body, but it will not stop anyone who knows what they are doing when it comes to digital image manipulation.
If you are one in a million, then there are six thousand people who are just like you.
I realize it isn't as simple as flipping 0's & 1's but you get the general picture.
[Fuck Beta]
o0t!
"Seems as though it would be a computationally intensive but a logically easy task."
Probably. Consider this, though: Fingerprints are common knowledge. We ALL know that if we commit a crime, fingerprints will be lifted to try to catch us. There are well known ways to defeat this, but remarkably, LOTS of people are still leaving fingerprints as clues at a crime.
I hope you can forgive me for reading a little more into your post than you actually said. I don't know for sure if you were going the "this could easily be defeated, thus it is ineffective" route. But I thought this would be as good of time as any to mention this.
"Derp de derp."
Most of the early photos you come across were staged. Taking a photograph was a big deal. People dressed up in their best outfits and the photographer would construct the scene. Often the photographer colored or otherwise enhanced the image. Photography has always been an art form. As an art form, people choose the message to convey.
Using photographs as evidence has always been problematic. The struggle is for lawyers to keep enough faith in photos to be able to use them in court. Personally, I think having a method to declare a photography mathematically correct immediately creates a problem where people with sufficient resources to fake mathematically correct fake photos will have the ability to manipulate the courts.
There never was that much faith in photographic evidence. I think we are better of having doubts about photographic evidence than we will be if we sanctify any photos as mathematically correct. The methods will have some value in quickly identifying tampered evidence, but will not have value in verifying it.
OK, if we're going to have this conversation, we need to define what we mean by "fake photograph." Yes, many photos were staged, particularly when taking photos was significantly more difficult than "point and shoot." But a staged photograph is not a fake photograph - it's still a reasonably accurate representation of reality as it existed at the time the photo was taken.
You're also quite correct that photos are routinely manipulated in the dark room. However, manipulating the color and otherwise enhancing the image is not at all what most people mean by a "fake photograph." There's a fundamental difference in those types of manipulations and putting Sarah Michelle Gellar's head on a porn star's body or putting John Kerry and Jane Fonda on the same podium together. This type of thing was possible before, but it was much, much more difficult and much less common.
"The legitimate powers of government extend only to such acts as are injurious to others." Thomas Jefferson.