From: Pavel Machek Subject: Re: random(4) changes Date: Tue, 26 Apr 2016 21:41:55 +0200 Message-ID: <20160426194155.GB11111@amd> References: <20160426030735.GD28496@thunk.org> <20160426184439.GA8162@amd> <1948798.MKebf3xYm7@positron.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Theodore Ts'o , Sandy Harris , LKML , linux-crypto@vger.kernel.org, Jason Cooper , John Denker , "H. Peter Anvin" , Andi Kleen To: Stephan Mueller Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:46862 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752967AbcDZTl6 (ORCPT ); Tue, 26 Apr 2016 15:41:58 -0400 Content-Disposition: inline In-Reply-To: <1948798.MKebf3xYm7@positron.chronox.de> Sender: linux-crypto-owner@vger.kernel.org List-ID: Hi! > > > > When dropping the add_disk_randomness function in the legacy > > > > /dev/random, I > > > > would assume that without changes to add_input_randomness and > > > > add_interrupt_randomness, we become even more entropy-starved. > > > > > > Sure, but your system isn't doing anything magical here. The main > > > difference is that you assume you can get almost a full bit of entropy > > > out of each interrupt timing, where I'm much more conservative and > > > assume we can only get 1/64th of a bit out of each interrupt timing. > > > > Maybe 1/64th of a bit is a bit too conservative? I guess we really > > have more than one bit of entropy on any system with timestamp > > counter.... > > > > Making it 1/2 of bit (or something) should be very easy way to improve > > entropy early during boot... > > I can easily settle on 1/2 bit here. The LRNG currently uses 0.9 bits which > are based on measurements plus a safety margin. But I see no issue to even > lower it further to, say, 1/2. No, you don't need to change anything. But maybe mainline rng should change. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html