svn commit: r239569 - head/etc/rc.d

[David O'Brien]

On Tue, Sep 11, 2012 at 03:01:25PM -0600, Ian Lepore wrote:
> On Tue, 2012-09-11 at 13:09 -0700, David O'Brien wrote:
> > Good to see someone have thoughts on this.  I've only seen it stated
> > that entropy passes thru mostly "untouched" thru a cryptographic hash
> > in the literature.
...
> Whether the same might be true of a hash is an interesting question,
> since it discards information rather than just changing the way it's
> encoded.

Ian,
This is a key point of Yarrow's design.

See http://www.schneier.com/paper-yarrow.ps.gz
in 5 'The Generic Yarrow Design an Yarrow-160'

    The reason is if you take an 'm' bit random value and apply a hash
    function that produces 'm' bits of output, the result has less than
    'm' bits of entropy due to the collisions that occur.  This is a very
    minor effect, and overall results in the loss of at most a few bits
    of entropy.

-- 
-- David  (obrien at FreeBSD.org)