[coyotos-dev] Some comments on Coyotos Microkernel Specification
Jonathan S. Shapiro
shap at eros-os.org
Mon Dec 5 17:22:27 EST 2005
On Mon, 2005-12-05 at 14:53 -0700, Christopher Nelson wrote:
> > Christopher Nelson wrote:
> > >I fail to see how this disproves what I said.
> > >
> > Odds of 4294967296 to 1 are not "astronimical", they are
> > squarely in the realm of possible for someone with some time
> > on their hands and a spare computer.
> I guess I don't understand your point. What I'm saying is that
> SHA-1 is "sufficiently unique" for interface id generation. What
> are you saying?
> I also don't see where the 42949...96 number enters. A 64-bit number is
> much larger than 4gigs of address.
That isn't relevant. Let's back up and do this right.
First, as Dominique said, SHA-1 generates a 160 bit hash, so forget the
64 bit thing entirely.
Given a 160 bit cryptographic hash, you get about 2^80 reliably
non-colliding values. Yes, this is quite a lot.
But in any case the entire discussion is moot, because the *input* to
the hash is not taken from a non-colliding space, and the hash output is
a deterministic function of its input.
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