Re: [RFC][PATCH] Make cryptoapi non-optional?

Andries Brouwer
2003-08-15T17:04:15Z

On Fri, Aug 15, 2003 at 10:03:24AM -0500, Matt Mackall wrote:
> On Fri, Aug 15, 2003 at 09:30:03AM +0200, Andries Brouwer wrote:
> > On Thu, Aug 14, 2003 at 06:17:13PM -0600, Val Henson wrote:
> >
> > > See Matt Mackall's earlier post on correlation, excerpted at the end
> > > of this message. Basically, with two strings x and y, the entropy of
> > > x alone or y alone is always greater than or equal to the entropy of x
> > > xored with y.
> > >
> > > entropy(x) >= entropy(x xor y)
> > > entropy(y) >= entropy(x xor y)
> >
> > Is this trolling? Are you serious?
> > Try to put z = x xor y and apply your insight to the strings x and z.
>
> Val left out the assumption that x and y are already perfectly
> distributed, in and of themselves.

I see. "Perfectly distributed" does not sound like a good technical term.
Surely you do not mean "uniformly distributed".
Maybe you mean: "of maximal possible entropy?".

Then the statement has nothing to do with the xor and is just
entropy(x) >= entropy(a)
assuming that x has maximal possible entropy.

Well, yes, indeed.