At 08:09 PM 12/11/03 -0500, Tyler Durden wrote:

As for Variola's comment, you might be right. I just assumed there's

some

kind of relationship between LSB and those spatial freuencies wherein image information might be stored. Actually, I would still think there's a relationship, in which case an Echelon-like approach based on ffts and "noise templates" might be going on (hence the usefulness of jamming).

Anyone got a TLA Operative Handbook? ANy mention in there of what kind of photos are best for Stego? How about cloud photos? (particularly where

I'm not saying that you could never use FT to detect weaker kinds of stego. But if information is encoded as say the parity of 3 LSBits from different regions of the image, good luck. there

are clouds of many different shapes and sizes present in the photo simultaneously.)

The most important thing is not to put too much cargo in your carrier. Think in terms of signal to noise if you wish. Obviously a picture with truly uniform color fields ---like a digital cartoon-- won't be useful. But scanning a piece of paper does not have this problem, for say 8 bits per grayscale pixel. Because each analog scan of the same piece of paper gives different bits. TD, you surely have the background to look into this stuff (and stego detection) if you want. BTW Stego ~aka watermarking. And stego can be done in music, movies, ascii text, etc. Or you could work from first principles, if you are able to mentally switch between steganographer and stego-detecter. (This same playing-chess-with-yourself is vital to security analysis, crypto, etc.)