Subject: Re: CVS commit: syssrc/sys/dev/ic
To: Perry E. Metzger <>
From: Wolfgang Rupprecht <>
List: tech-kern
Date: 11/10/2001 10:27:17
Perry E. Metzger writes:
> Wolfgang Rupprecht <> writes:
> > Would pushing the "would-be entropy" through a crypto-system make it
> > non-predictable enough to prevent such attacks?
> Imagine that you have a system that can produce 800 possible
> outputs. We put the 800 possible outputs through a hash function in
> order to obscure them. How many possible outputs are there from the
> hash function? Still just 800. You can trivially generate all 800
> possible states, hash them, and search the output space.

I agree.  That wasn't the suggestion though.  My initial msg mentioned
(perhaps too briefly) running the crypto unit in "chained feedback
mode".  That is, the current output is a function of the current input
and the last output.  The set of covered output states is as large as

Wolfgang Rupprecht    <>
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