Date: Thu, 20 Sep 2012 11:20:56 +0200 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: RW <rwmaillists@googlemail.com> Cc: freebsd-security@freebsd.org, Jonathan Anderson <jonathan.anderson@cl.cam.ac.uk>, Pawel Jakub Dawidek <pjd@FreeBSD.org>, Mariusz Gromada <mariusz.gromada@gmail.com> Subject: Re: Collecting entropy from device_attach() times. Message-ID: <86ipb9t5hj.fsf@ds4.des.no> In-Reply-To: <20120919231051.4bc5335b@gumby.homeunix.com> (RW's message of "Wed, 19 Sep 2012 23:10:51 %2B0100") References: <20120918211422.GA1400@garage.freebsd.pl> <A8FD98DD94774D00B4E5F78D3174C1B4@gmail.com> <20120919192923.GA1416@garage.freebsd.pl> <20120919205331.GE1416@garage.freebsd.pl> <20120919231051.4bc5335b@gumby.homeunix.com>
next in thread | previous in thread | raw e-mail | index | archive | help
RW <rwmaillists@googlemail.com> writes: > You're basing a model for all devices on a single sound card, that > doesn't seem safe to me. Isn't it possible that a device could take a > long and well defined time? Please understand that the timers used here have a resolution of around 1e-8 to 1e-10 seconds. You may be able to predict the first six digits with reasonable accuracy - in fact, the first four or five will almost always be 0, except for devices with moving parts - but anything beyond that is a crapshoot, even in a virtual machine. (I am speaking, of course, of decimal digits - multiply by 3.322 for the corresponding number of bits) DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?86ipb9t5hj.fsf>