Has this photo been de-stegoed?

[Tyler Durden]

OK...let's say I receive a photo that I expected to contain stegoed 
information on it,  but then find that there's nothing I can retrieve using 
the likely methods or software.

Is it possible to determine that the photo 'originally' (ie, when it was 
sent to me) contained stegoed information, but that it was intercepted in 
transit and the real message overwritten with noise or whatever?

Now I know pretty much nothing about this subject, but I would suppose that 
de-stegoing a photo must like some kind of spatial spectral fingerprint that 
should be visible after the photo is FFT'd (is there freeware software out 
there?).

Now I IMAGINE that a sophisticated interceptor could substitute 'believable' 
de-stego-ing noise so that it would look like the photo never had any stego 
in the first place. OR...is this actually 'impossible' to do perfectly?

And then, what if the interceptor tried to put an alternate message in there 
instead? Is there a way to tell that there was originallya different message 
there?

My assumption first of all is that nothing was done to prepare the photo 
against these possibilities. A simple stego message was placed without real 
thought about whether it might be intercepted and altered.

-TD

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