Date: Mon, 19 Aug 2013 08:13:53 +0100 From: Mark R V Murray <mark@grondar.org> To: Warner Losh <imp@bsdimp.com> Cc: Tim Kientzle <tim@kientzle.com>, FreeBSD-arch Arch <freebsd-arch@freebsd.org>, secteam@freebsd.org, =?iso-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no> Subject: Re: random(4) plugin infrastructure for mulitple RNG in a modular fashion Message-ID: <3513A465-AD8D-4DDC-9408-2F89F9B86404@grondar.org> In-Reply-To: <12B58C72-CFE3-4AD4-AD03-462A10E431D9@bsdimp.com> References: <20130807183112.GA79319@dragon.NUXI.org> <86pptfnu33.fsf@nine.des.no> <20130815231713.GD76666@x96.org> <20130816002625.GE76666@x96.org> <9B274F48-0C88-4117-BEAC-1A555772A3C5@grondar.org> <86a9kf733d.fsf@nine.des.no> <0C97B866-A169-4141-8368-AA7F5B5382F4@grondar.org> <861u5r71zi.fsf@nine.des.no> <892B11BD-396D-4F82-B97C-753F72CA494D@grondar.org> <86r4dr5j3p.fsf@nine.des.no> <4C1BD77C-8C6B-4044-9285-5978A3BC4B70@kientzle.com> <12B58C72-CFE3-4AD4-AD03-462A10E431D9@bsdimp.com>
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--Apple-Mail=_FB4B5D4A-A92B-46C9-B973-2C04BF738D45 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 On 19 Aug 2013, at 08:09, Warner Losh <imp@bsdimp.com> wrote: >> Besides Yarrow and Fortuna mixers, we could then >> offer a "null mixer" option that selected the single >> "best" entropy source and passed it directly through. >=20 > I'm still wondering why timecounters aren't the right model to follow = here, where you can have several compiled into the kernel and the one = with the best score wins. How would they get a score, and how would it be decided which is better? = How is the score "calibrated"? >> Users could compile the null mixer into the kernel >> and load a single HW RNG driver to have precise >> control over /dev/random. Interrupt harvesting would >> be the lowest-quality source as a fall back. >>=20 >> In particular, this has a reasonable failure mode if >> someone built a kernel with only a single HW entropy >> source and the null mixer: >> * On hardware with that source, they would get >> full-speed HW entropy. >> * On hardware without that source, they would get >> the old blocking /dev/random that we had before >> Yarrow, the one that used only interrupt harvesting. >=20 > Assuming there was enough interrupt entropy to generate bits=85 See Ferguson & Schneier on this (qv my follow-up). M --=20 Mark R V Murray --Apple-Mail=_FB4B5D4A-A92B-46C9-B973-2C04BF738D45 Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.20 (Darwin) Comment: GPGTools - http://gpgtools.org iQCVAwUBUhHFt958vKOKE6LNAQpttwP8DqaLAcLTQEWdfQCdrZkv+hdk/Rt5dPXT FIYqkknkPoLX6Ly6dyUmlOLtFAsyAkG428Y8gpN28pi/WkTIc5WHq/B2XMJsmDWN Zl2P0HeGH1IqrmwioKGBE92hASJ6x8hosmICFN7mkf5DVTUDs7NVkChHPPl31DG7 J9+w81Re2Xo= =zMFZ -----END PGP SIGNATURE----- --Apple-Mail=_FB4B5D4A-A92B-46C9-B973-2C04BF738D45--
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