3 ms·
How would an adversary break this? My first idea would be to rotate it by something that's halfway between the steps used. Say, 360/32 degrees. How does that c
by TheLoneWolfling 12y ago
How would an adversary break this?
My first idea would be to rotate it by something that's halfway between the steps used. Say, 360/32 degrees. How does that compare?
Also: because it discards the high frequency data one should be able to construct something like this: http://cvcl.mit.edu/hybrid/CatDogHybrid.jpg http://cvcl.mit.edu/hybrid/CatDogHybrid.jpg - where to us at a close distance it looks like one thing but to this it looks like something else.
- bcoates 12y agoIt would be pretty easy to assign any image an arbitrary value. Compare the image's current (unquantized) DCT values to the desired ones, find the value that differs from the target but is closest to being quantized as the desired bit, and apply a filter that just barely flips it. Each time you do this you reduce the Hamming distance score between the image and the target by 1. If getting close enough results in unsightly blotches on the image, reduce the power of the low frequency luminance channel across the board, which will mask the changes by making the unmodified high frequency components more noticeable. That looks like what's being done in the catdog image, at least. You could increase the saturation as well, as this fingerprinting system ignores color.