Date: Tue, 11 Sep 2012 16:01:17 -0700 From: Xin Li <delphij@delphij.net> To: Arthur Mesh <arthurmesh@gmail.com> Cc: Doug Barton <dougb@FreeBSD.org>, freebsd-rc@freebsd.org, obrien@freebsd.org, freebsd-security@freebsd.org, RW <rwmaillists@googlemail.com>, Dag-Erling ??? <des@des.no>, d@delphij.net Subject: Re: svn commit: r239569 - head/etc/rc.d Message-ID: <504FC2BD.6070402@delphij.net> In-Reply-To: <20120911224855.GE14077@x96.org> References: <20120911061530.GA77399@dragon.NUXI.org> <504EDC67.9070700@FreeBSD.org> <86sjao7q8c.fsf@ds4.des.no> <20120911205302.27484fd6@gumby.homeunix.com> <20120911200925.GA88456@dragon.NUXI.org> <504FA76A.5000209@delphij.net> <20120911211730.GB89188@dragon.NUXI.org> <504FAB87.3020701@delphij.net> <20120911215212.GA89515@dragon.NUXI.org> <504FBD15.8040907@delphij.net> <20120911224855.GE14077@x96.org>
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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 On 09/11/12 15:48, Arthur Mesh wrote: > On Tue, Sep 11, 2012 at 03:37:09PM -0700, Xin Li wrote: >> Using gzip is better than not using it though, since 4k worth of >> compressed data is better than 4k worth of plain text because of >> higher entropy destiny (note that the FreeBSD gzip uses 64K of >> input/output buffer for compression by the way so maybe only the >> first 64K is meaningful if we take only 4k of output). > > Since there is 1:1 correspondence between compressed and > uncompressed data, entropy should be the same in both. I am not > sure it's better to use compression than not -- you do end up > seeding fewer bytes to yarrow, but you spend more CPU cycles > compressing it... Well, 1:1 correspondence is when we fed full text to /dev/random, which we don't, right? Only the first 4K gets consumed. So: Situation 1: we have 45K of plain text, and only first 4k is fed to /dev/random at about 5 bits of entropy per byte; Situation 2: we have 45K of plain text, compress to e.g. 25K and only first 4k is fed to /dev/random at more than 7.6 bits of entropy per byte; Therefore I think Situation 2 is better than situation 1. Cheers, - -- Xin LI <delphij@delphij.net> https://www.delphij.net/ FreeBSD - The Power to Serve! Live free or die -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBCAAGBQJQT8K9AAoJEG80Jeu8UPuzdpAH/0yoP6LUeBTufuRG21olIWf0 Z8fAaJHPOplhNsiD8SCvZn2nep/FvUH4MARqVWeZ0GqcM9Yqz669WMEyDohWvufo TxjSDw+CmAZie+7IpBsyWmOWzqiaOG4RhCRed4KlKnJYWaBfxUDIQMOhpNANKVJY kL1TwI5dhz8twCMQiGLq/y975Sn7MegdoNTTCjLWBDJN9bCrH/8PnqJoXtd4KClP Jzu+ywbM1CwF+TV+g1QnfhFqZp8Gke0CSpZTNko0Vsk9XGJvHe0XmVxvlg7YYwJm zoXixJSbpdQsBuwUkzsrYK0nDIRLEbEIdh20Vi5aW1a9MBNsVSP/3lguuyz0Ntc= =o47Q -----END PGP SIGNATURE-----
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