<nettime> "Pirate Utopia," FEED, February 20, 2001

[Ray Dillinger]

On Mon, 24 Sep 2001, Nomen Nescio wrote:

>The Stegdetect paper proceeded to further analyze the 20000+ images by
>looking for passwords that would produce meaningful messages from the
>hypothesized hidden content, via dictionary attack.  No valid passwords
>were found, and the authors concluded therefore that these were all
>false positives.  This does not seem to be a fully supported conclusion.

Actually, dictionary attacks reveal about sixty percent of passwords, 
so for every six passwords you find on a dictionary attack, you can 
infer ten actual stegotexts times the ratio between your analyzed and 
discovered (possibly-false) positives.  

While he has analyzed only two percent of his sample, that's a sufficient 
number that if even even a tenth of one percent of his positives were 
real he'd have discovered at least a few passwords. 

The paper is solid statistical methods; lack of any dictionary-yeilding 
passwords in that big a sample is very strong evidence that the sample 
is overwhelmingly made up of false positives.

				Bear




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