[free-sklyarov] Bruce Perens on Dmitry

Paul Callahan callahanpb at yahoo.com
Thu Aug 2 08:23:47 PDT 2001

The zdnet article has a link to David Touretzky's web
where you can find Dmitry's slides.  Here is the link
in gif/html format:


I had mentioned that I was curious to see what exactly
Sklyarov had done to decrypt Adobe eBooks, and I can
see that it was indeed a very weak system. 

The part I found confusing in the zdnet article was
the part about XORing the text with the word 
"encrypted". It's more clear from the slide. 
you'd XOR each character in succession with the
next letter of the keyword (which is already easily
breakable).  I.e.

   This is some coded text.
Instead each letter is XOR'd with all the characters
in "encrypted". This is identical to forming one
byte as the XOR of these characters and applying it
to every character.  So the code is arguably
weaker than a newspaper cryptogram, which is also
a simple substitution cipher but without such an
obvious pattern.

It sounds to me like Adobe ought to be suing its
outsourcers if it really must take legal action
against someone.


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