From: tomw@orac.engr.sgi.com (Tom Weinstein)
To: cypherpunks@toad.com
Message Hash: e4c6db642f0ef423322fe1be0a699ac43ea56ca8a9125f0c72e2afd5064abf29
Message ID: <199510311648.IAA05877@orac.engr.sgi.com>
Reply To: <DHAMpE.34y@sgi.sgi.com>
UTC Datetime: 1995-11-01 00:41:50 UTC
Raw Date: Wed, 1 Nov 1995 08:41:50 +0800
From: tomw@orac.engr.sgi.com (Tom Weinstein)
Date: Wed, 1 Nov 1995 08:41:50 +0800
To: cypherpunks@toad.com
Subject: Re: /dev/random for FreeBSD [was: Re: /dev/random for Linux]
In-Reply-To: <DHAMpE.34y@sgi.sgi.com>
Message-ID: <199510311648.IAA05877@orac.engr.sgi.com>
MIME-Version: 1.0
Content-Type: text/plain
In article <DHAMpE.34y@sgi.sgi.com>, "Theodore Ts'o" <tytso@MIT.EDU> writes:
> Date: Mon, 30 Oct 1995 21:59:14 -0500
> From: "Josh M. Osborne" <stripes@va.pubnix.com>
> When /dev/random doesn't have "enough" enthropy left does reading
> from it return an error, or block? I would strongly suggest
> blocking, as the non-blocking behavur is not really all that useful.
> It acts like many character devices and named pipes in that if there is
> no entropy available at all, it blocks. If there is some entropy
> available, but not enough, it returns what is available. (A subsequent
> read will then block, since no entropy will then be available.)
> Actually, what's currently in Linux doesn't work precisely like this,
> but it will soon. After talking a number of people on both sides of the
> block vs. non-blocking camp, this seemed to be a suitable compromise.
> At least one Major Workstation Vendor is planning on using this behavior
> for their /dev/random, to appear in a future OS release. If we all can
> standardize on this behavior, it'll make application writer's jobs that
> much easier.
One problem with this scheme is that if multiple processes have
/dev/random open you can block unexpectedly. If I try to avoid blocking
by first checking if entropy is available there's a race condition if
another process reads from the device. Is there another way to avoid
blocking?
--
Sure we spend a lot of money, but that doesn't mean | Tom Weinstein
we *do* anything. -- Washington DC motto | tomw@engr.sgi.com
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