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Open Source and information security mailing list archives
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Date: Tue, 4 Dec 2007 14:36:36 -0600 From: Matt Mackall <mpm@...enic.com> To: Theodore Tso <tytso@....edu>, Alan Cox <alan@...rguk.ukuu.org.uk>, Ray Lee <ray@...rabbit.org>, Adrian Bunk <bunk@...nel.org>, Marc Haber <mh+linux-kernel@...schlus.de>, linux-kernel@...r.kernel.org Subject: Re: Why does reading from /dev/urandom deplete entropy so much? On Tue, Dec 04, 2007 at 02:50:21PM -0500, Theodore Tso wrote: > On Tue, Dec 04, 2007 at 12:02:37PM -0600, Matt Mackall wrote: > > On Tue, Dec 04, 2007 at 04:55:02PM +0000, Alan Cox wrote: > > > > cryptographically strong stream it'll provide when /dev/random is > > > > tapped? In principle, this'd leave more entropy available for > > > > applications that really need it, especially on platforms that don't > > > > generate a lot of entropy in the first place (servers). > > > > > > > > > As reported about a month ago, the evidence is that the /dev/random > > > stream is not cryptographically strong. Collecting uuids generated from > > > the kernel uuid random generator from the random generator in the kernel > > > shows abnormal patterns of duplicates. > > > > Pointer, please. > > Alan, are you sure you're not talking about Helge Deller's attempt to > push a Time-based UUID generator into the kernel because you can get > duplicates from the current userspace library? > > I've not heard of *any* claim where the kernel uuid random generator > has been returning duplicates. Before we added proper locking, it could theoretically happen on SMP with readers in lockstep. That was early 2.6. The only serious critique I know of is the Gutterman-Pinkas-Reinman paper which was a year out of date before publication. Now that another year has passed, perhaps I should respond to it.. -- Mathematics is the supreme nostalgia of our time. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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