From owner-freebsd-current Wed Jul 19 10:42:43 2000 Delivered-To: freebsd-current@freebsd.org Received: from rover.village.org (rover.village.org [204.144.255.49]) by hub.freebsd.org (Postfix) with ESMTP id 21A3937B689; Wed, 19 Jul 2000 10:42:39 -0700 (PDT) (envelope-from imp@harmony.village.org) Received: from harmony.village.org (harmony.village.org [10.0.0.6]) by rover.village.org (8.9.3/8.9.3) with ESMTP id LAA93088; Wed, 19 Jul 2000 11:42:37 -0600 (MDT) (envelope-from imp@harmony.village.org) Received: from harmony.village.org (localhost.village.org [127.0.0.1]) by harmony.village.org (8.9.3/8.8.3) with ESMTP id LAA82840; Wed, 19 Jul 2000 11:42:35 -0600 (MDT) Message-Id: <200007191742.LAA82840@harmony.village.org> To: Alexander Leidinger Subject: Re: randomdev entropy gathering is really weak Cc: mark@grondar.za, current@FreeBSD.ORG, phk@FreeBSD.ORG In-reply-to: Your message of "Tue, 18 Jul 2000 18:01:00 +0200." <200007181601.SAA02045@Magelan.Leidinger.net> References: <200007181601.SAA02045@Magelan.Leidinger.net> Date: Wed, 19 Jul 2000 11:42:35 -0600 From: Warner Losh Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In message <200007181601.SAA02045@Magelan.Leidinger.net> Alexander Leidinger writes: : systems which have a more or less precise clock attached (e.g. GPS or : atomic clocks which sync the system clock via nptd)? And what are the : numbers for this solution (for those people which are interested in : numbers to be their own judge)? I can tell you right now that the variation between GPS and a good cesium clock is on the order of +- 25ns. With nanosecond resolution, this gives you about 5 bits. The variation of the system clock when synchronized to the GPS receiver is on the order of +-10us as measured with a parallel port interrupt and a pps line from the gps receiver. The pps interrupt is measured using a fast interrupt (we hacked ppc to do fast interrupts for this), so the latency is fairly small and fairly constant. I don't have datasets that I can point people at, however. Warner To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message