From: Paulo Marques <pmarques@grupopie.com>
To: linux-os@analogic.com
Cc: "Patrick J. LoPresti" <patl@curl.com>,
Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: /dev/random vs. /dev/urandom
Date: Mon, 10 Jan 2005 13:03:37 +0000 [thread overview]
Message-ID: <41E27D29.2040001@grupopie.com> (raw)
In-Reply-To: <Pine.LNX.4.61.0501100735210.19253@chaos.analogic.com>
linux-os wrote:
> [...]
> One is free to use any number of samples. The short number of samples
> was DELIBERATELY used to exacerbate the problem although a number
> or nay-sayers jumped on this in an attempt to prove that I don't
> know what I'm talking about.
It seems to me that you actually don't.
Since this is a *uniform* distribution in the range [0..2^N[, than any
of those N bits must also show a uniform distribution, or the
distribution of the sum of the bits wouldn't be uniform. (isn't this
obvious?)
It would be different of course, if this was not a uniform distribution,
or the range was not a power of 2...
Of course, I agree that throwing away 5 bits in every byte of perfect
entropy that the kernel worked so hard to gather is just wrong, but the
randomness of the result is not the reason why.
> In the first place, the problem was to display the error of using
> an ANDing operation to truncate a random number. In the limit,
> one could AND with 0 and show that all randomness has been removed.
Not really.. you just get a perfect random uniform distribution if the
range [0..0] :)
--
Paulo Marques - www.grupopie.com
"A journey of a thousand miles begins with a single step."
Lao-tzu, The Way of Lao-tzu
next prev parent reply other threads:[~2005-01-10 13:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-01-07 19:05 /dev/random vs. /dev/urandom Ron Peterson
2005-01-07 19:16 ` Paulo Marques
2005-01-07 19:24 ` Chris Friesen
2005-01-07 19:26 ` Florian Weimer
2005-01-07 19:27 ` linux-os
2005-01-07 19:40 ` Robert Love
2005-01-07 20:50 ` Ron Peterson
2005-01-07 21:39 ` Andries Brouwer
2005-01-07 22:39 ` linux-os
2005-01-07 17:55 ` Michal Schmidt
2005-01-07 23:29 ` Andries Brouwer
2005-01-08 17:34 ` Patrick J. LoPresti
2005-01-10 12:41 ` linux-os
2005-01-10 13:03 ` Paulo Marques [this message]
2005-01-10 14:39 ` Felipe Alfaro Solana
2005-01-10 15:13 ` Patrick J. LoPresti
2005-01-10 19:24 ` David Schwartz
2005-01-11 14:38 ` Andrea Arcangeli
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