Re: [PATCH] (0/4) Entropy accounting fixes

[dean gaudet]

On Mon, 9 Sep 2002, Oliver Xymoron wrote:

> making the RNG guessable is relatively easy. On the other hand
> determining whether a given snippet of code is doing RSA, etc. is
> equivalent to solving the halting problem, so it's seems to me pretty
> damn hard to usefully put this sort of back door into a CPU without
> sacrificing general-purpose functionality.

while the general problem is certainly halting-problem level of
complexity, there's a much more simple problem which amounts to string
matching.  the simple problem is "is this a specific portion of openssl /
cryptoapi / whatever?"

if you consider a technology like transmeta's which only has to
compile/translate code infrequently (rather than a traditional technology
with decoders running all the time) then it's pretty easy to see how you
could use a few cycles to do the string matching.

people have been doing this in compilers for years, where the string
matching question is "is this part of SPECCPU?"

-dean