From owner-freebsd-current Sun Jul 23 18:25:36 2000 Delivered-To: freebsd-current@freebsd.org Received: from freefall.freebsd.org (freefall.FreeBSD.ORG [204.216.27.21]) by hub.freebsd.org (Postfix) with ESMTP id 77B3937B6CE; Sun, 23 Jul 2000 18:25:34 -0700 (PDT) (envelope-from kris@FreeBSD.org) Received: from localhost (kris@localhost) by freefall.freebsd.org (8.9.3/8.9.2) with ESMTP id SAA85568; Sun, 23 Jul 2000 18:25:34 -0700 (PDT) (envelope-from kris@FreeBSD.org) X-Authentication-Warning: freefall.freebsd.org: kris owned process doing -bs Date: Sun, 23 Jul 2000 18:25:34 -0700 (PDT) From: Kris Kennaway To: "Jeroen C. van Gelderen" Cc: Mark Murray , current@FreeBSD.ORG Subject: Re: randomdev entropy gathering is really weak In-Reply-To: <397B4090.6A15442E@vangelderen.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Sun, 23 Jul 2000, Jeroen C. van Gelderen wrote: > > Well, a simple scheme which doesn't seem to suffer from any of the > > vulnerabilities discussed in the schneier papers is to accumulate entropy > > in a pool, and only return output when the pool is full. i.e. the PRNG > > would either block or return 0 bytes of data, or a full pool's worth. > > And you can make Yarrow do just that. Not very practical but > you can do it. You effectively set Pg to 1/(2^(k/3)). Oh, I missed this - thanks. It does introduce an extra overhead, namely applying a generator gate with every output (since n < k and Pg < 1) and then the full reseed with every k bits of output. ITYM Pg = k 2^(-k/3) though - you want a maximum k bits of output, not 1. I'm not sure if the current implementation will let you do this (since Pg < 1 here). > Reseeds do not *have* to happen asynchronously as pointed out > above. Yeah, but they do in the current implementation (AFAICT). Kris -- In God we Trust -- all others must submit an X.509 certificate. -- Charles Forsythe To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message