31–39 of 39 posts
About a year ago when AI was getting really big, I was really interested in C2PA, since then I've come to the conclusion that actual artists don't care about any of that crap
You can probably build a rig to feed false data to the sensor, or take a photo of a sufficiently high-resolution display, or use side-channel power analysis to extract the cryptographic keys. I have serious doubts this kind of provenance metadata will actually work against a sophisticated attacker (someone willing to spend more than 100k on making fake images), but I'm sure it will be used as an excuse to further loc…
Then why not replace the sensor entirely and send fake sensor data? It would be difficult to fake depth of field changes in response to camera's focus motor moving. If I were a security researcher, I would really try to see if the camera is smart enough to tell if the sensor data is fake.
> take a photo of a sufficiently high-resolution display
A 60 MP display? (10000x6000 resolution? I want one!!!) That would still make pixels visible. I suspect a display at least 4x larger would be needed. And it needs to be curved, or the out-of-focus corners will ruin the illusion.
Earlier quoted context omitted.
Without any visible artifacts? I would imagine that to be quite difficult actually!
Cameras are used to scan analog film. I have used it in the past, it works perfectly and there is no way for you to tell it was scanned this way. But here is an alternative: You pass an image through a lens, you take photo from the camera. Now, having the input original AI-generated image and photo with the artifacts you calculate what changes your camera introduces. You reverse it to know what needs to be modified i…
Also, you would need a curved spherical display, or the camera won't be able to focus on it's center and corners at the same time.
What photographic analog film has at least a 60 MP resolution without any blur or dim colors? How would you transfer a digital fake image on that film? How would you take a picture of that film without losing even more resolution, color, sharpness?
Earlier quoted context omitted.
Cameras are used to scan analog film. I have used it in the past, it works perfectly and there is no way for you to tell it was scanned this way. But here is an alternative: You pass an image through a lens, you take photo from the camera. Now, having the input original AI-generated image and photo with the artifacts you calculate what changes your camera introduces. You reverse it to know what needs to be modified i…
How would you display the fake image in front of the camera? That camera has a 60 MP sensor. That about 10'000 x 6'000 pixels. Eight times higher than a 8K display! Also, you would need a curved spherical display, or the camera won't be able to focus on it's center and corners at the same time. What photographic analog film has at least a 60 MP resolution without any blur or dim colors? How would you transfer a digit…
Second, no you do not need a spherical display. Depth of field IS A PLANE. Also, photographing analog film is done from good enough distance to get rid of any curvature for the practical purposes.
Third, photographic analog films can have hundreds of MPs. But it does not matter, the choice of medium you present to the camera is yours and it does not have to be analog film. I am just giving analog film as an example because it is high resolution compared to even best prints or digital displays.
Fourth. Before you start saying something is not possible, would you mind to do an even most basic cursory search? Here is an example of people doing this professionally with a DSLR: https://www.youtube.com/watch?v=BVmIhwG0XfU
Earlier quoted context omitted.
How would you display the fake image in front of the camera? That camera has a 60 MP sensor. That about 10'000 x 6'000 pixels. Eight times higher than a 8K display! Also, you would need a curved spherical display, or the camera won't be able to focus on it's center and corners at the same time. What photographic analog film has at least a 60 MP resolution without any blur or dim colors? How would you transfer a digit…
First, you mistakenly assume every photo of note is sharp. That's absolutely not true. Second, no you do not need a spherical display. Depth of field IS A PLANE. Also, photographing analog film is done from good enough distance to get rid of any curvature for the practical purposes. Third, photographic analog films can have hundreds of MPs. But it does not matter, the choice of medium you present to the camera is you…
I still can't see how the digital fake could be transfered to analog film at that resolution or what other means of presenting the fake image in front of the camera might produce non-obvious-fake digital images.
You can probably build a rig to feed false data to the sensor, or take a photo of a sufficiently high-resolution display, or use side-channel power analysis to extract the cryptographic keys. I have serious doubts this kind of provenance metadata will actually work against a sophisticated attacker (someone willing to spend more than 100k on making fake images), but I'm sure it will be used as an excuse to further loc…
> feed false data to the sensor Then why not replace the sensor entirely and send fake sensor data? It would be difficult to fake depth of field changes in response to camera's focus motor moving. If I were a security researcher, I would really try to see if the camera is smart enough to tell if the sensor data is fake. > take a photo of a sufficiently high-resolution display A 60 MP display? (10000x6000 resolution?…
You can probably build a rig to feed false data to the sensor, or take a photo of a sufficiently high-resolution display, or use side-channel power analysis to extract the cryptographic keys. I have serious doubts this kind of provenance metadata will actually work against a sophisticated attacker (someone willing to spend more than 100k on making fake images), but I'm sure it will be used as an excuse to further loc…
There are probably many possible methods to detect a picture being of a display rather than the real world. The easiest clues are depth of field and focal length metadata mismatching (presumably a macro lens or similar would be needed, and also presuming lens metadata is not spoofable and included in the signed metadata). Color accuracy will be subtly off. Cameras can detect more dynamic range depth than most (any) s…
What DoF/focal length metadata?