From: Thomas Gleixner Subject: Re: [PATCH 4/5] tsc: wire up entropy generation function Date: Fri, 17 Jun 2011 22:58:42 +0200 (CEST) Message-ID: References: <1308002818-27802-1-git-send-email-jarod@redhat.com> <1308002818-27802-5-git-send-email-jarod@redhat.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Jarod Wilson , linux-crypto@vger.kernel.org, Matt Mackall , Ingo Molnar , John Stultz , Herbert Xu , "David S. Miller" , "H. Peter Anvin" , Suresh Siddha To: Venkatesh Pallipadi Return-path: Received: from www.linutronix.de ([62.245.132.108]:60134 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755809Ab1FQU6t (ORCPT ); Fri, 17 Jun 2011 16:58:49 -0400 In-Reply-To: Sender: linux-crypto-owner@vger.kernel.org List-ID: On Mon, 13 Jun 2011, Venkatesh Pallipadi wrote: > On Mon, Jun 13, 2011 at 3:06 PM, Jarod Wilson wrote: > > TSC is high enough resolution that we can use its low-order byte to > > stir new data into the random number generator entropy pool. > > >From what I vaguely remember from years past, rdtsc, especially last > few bits of it are not very good as random number source. As they are > based on lower bus frequency and a multiplier. May be things have > changed these days. Adding Peter and Suresh for comments. Recommended reading: https://www.osadl.org/fileadmin/dam/rtlws/12/Okech.pdf Thanks, tglx