Messages in this thread |  | | Date | Mon, 16 Sep 2002 20:18:34 -0500 | From | Oliver Xymoron <> | Subject | Re: [PATCH] (0/4) Entropy accounting fixes |
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On Mon, Sep 16, 2002 at 03:51:56PM -0700, dean gaudet wrote: > 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.
If you're the compiler, it's pretty damn easy. If you're the CPU watching the instruction stream generated by an unknown compiler for a lengthy piece of code with context switches and interrupts going on, it's back to being nontrivial again. It's simply much easier to backdoor the RNG..
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