This message generated a parse failure. Raw output follows here. Please use 'back' to navigate. From devnull@lkml.org Fri May 31 10:26:56 2024 Received: from entropy.muc.muohio.edu (IDENT:root@entropy.muc.muohio.edu [134.53.213.10]) by herbie.ucs.indiana.edu (8.9.3/8.9.3) with ESMTP id JAA16091 for ; Mon, 31 May 1999 09:15:25 -0500 (EST) Received: from vger.rutgers.edu (vger.rutgers.edu [128.6.190.2]) by entropy.muc.muohio.edu (8.8.7/8.8.7) with ESMTP id KAA02698; Mon, 31 May 1999 10:15:20 -0400 Received: by vger.rutgers.edu via listexpand id ; Mon, 31 May 1999 07:49:45 -0400 Received: by vger.rutgers.edu id ; Mon, 31 May 1999 06:03:34 -0400 Received: from lesser-magoo.lcs.mit.edu ([18.111.0.112]:24668 "EHLO lesser-magoo.lcs.mit.edu") by vger.rutgers.edu with ESMTP id ; Mon, 31 May 1999 04:03:11 -0400 Received: from miris.lcs.mit.edu (cananian@miris.lcs.mit.edu [18.111.0.89]) by lesser-magoo.lcs.mit.edu (8.8.7/8.8.7) with ESMTP id FAA01208; Mon, 31 May 1999 05:07:32 -0400 Date: Mon, 31 May 1999 05:07:31 -0400 (EDT) From: "C. Scott Ananian" X-Sender: cananian@miris.lcs.mit.edu To: Florian Weimer Cc: linux-kernel@vger.rutgers.edu Subject: Re: /dev/random and /dev/psaux: too much entropy assumed? In-Reply-To: Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-kernel@vger.rutgers.edu Precedence: bulk X-Loop: majordomo@vger.rutgers.edu X-Orcpt: rfc822;linux-kernel-outgoing-dig On 30 May 1999, Florian Weimer wrote: > After subtracting the timer interrupts, we get an average of over > nine bits added on each /dev/psaux interrupt to the /dev/random pool. > I don't think that there is that much entropy involved to justify this > high value. How many bits would you propose? Remember you've got several sources of randomness here: 1) time between mouse events (in processor cycles, usually) 2) x delta 3) y delta 4) button status Nine bits doesn't seem all that unreasonable to me. And if you care, why not distill it further. The techniques used to make very random numbers out of partially random numbers are well known. Speaking personally, I would like to see much more analysis of the sources of mouse randomness and the number of bits you think we can "reasonably" extract from these before you start throwing stones. Note that the kernel sources are open, so all the algorithms are in plain view. In particular, the algorithm used to calculate how many bits of 'true' randomness we're getting for each parcel of information added to the pot is in linux/drivers/char/random.c, and takes into account first and second order deltas to more accurately respond to how 'random' your input source currently is. I suspect during your test you were tossing the mouse around quite randomly, leading to a greater amount of entropy added to the pot than if you observed more 'natural' conditions with smaller mouse movements. --s @ @ =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-oOO-(_)-OOo-=-=-=-=-= C. Scott Ananian: cananian@lcs.mit.edu / Declare the Truth boldly and Laboratory for Computer Science/Crypto / without hindrance. Massachusetts Institute of Technology /META-PARRESIAS AKOLUTOS:Acts 28:31 -.-. .-.. .. ..-. ..-. --- .-. -.. ... -.-. --- - - .- -. .- -. .. .- -. PGP key available via finger and from http://www.pdos.lcs.mit.edu/~cananian SEAL Team 6 quiche struggle cracking assassination Sudan Noriega KGB Ft. Bragg Ortega Honduras Serbian Hawk DES nuclear fissionable UKUSA - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/