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From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: "Ahmed S. Darwish" <darwish.07@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	a.darwish@linutronix.de, LKML <linux-kernel@vger.kernel.org>,
	Nicholas Mc Guire <hofrat@opentech.at>,
	the arch/x86 maintainers <x86@kernel.org>,
	Andy Lutomirski <luto@kernel.org>,
	Kees Cook <keescook@chromium.org>
Subject: Re: x86/random: Speculation to the rescue
Date: Wed, 2 Oct 2019 08:01:15 -0400
Message-ID: <20191002120115.GA13880@mit.edu> (raw)
In-Reply-To: <20191001161448.GA1918@darwi-home-pc>

On Tue, Oct 01, 2019 at 06:15:02PM +0200, Ahmed S. Darwish wrote:
> 
> Using the "ent" tool, [2] also used to test randomness in the Stephen
> Müller LRNG paper, on a 500000-byte file, produced the following
> results:

The "ent" tool is really, really useless.  If you take any CRNG, even
intialized with a known seed, "ent" will say that it's *GREAT*!

If you don't believe me, disable all entropy inputs into the CRNG,
initialize it with "THE NSA IS OUR LORD AND MASTER", and then run it.
You'll get substantially the same results.  (And if we didn't the Cha
Cha 20 encryption algorithm would be totally broken).

       		  	    	     	     - Ted

  parent reply index

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-28 22:24 Thomas Gleixner
2019-09-28 23:53 ` Linus Torvalds
2019-09-29  7:40   ` Thomas Gleixner
2019-09-29  8:05   ` Alexander E. Patrakov
2019-09-30  1:16   ` Linus Torvalds
2019-09-30  2:59     ` Linus Torvalds
2019-09-30  6:10       ` Borislav Petkov
2019-09-30 16:06         ` Linus Torvalds
2019-10-01 13:51           ` Borislav Petkov
2019-10-01 17:14             ` Linus Torvalds
2019-10-01 17:50               ` [PATCH] char/random: Add a newline at the end of the file Borislav Petkov
2019-09-30 18:05         ` x86/random: Speculation to the rescue Kees Cook
2019-09-30  3:37     ` Theodore Y. Ts'o
2019-09-30 13:16       ` Theodore Y. Ts'o
2019-09-30 16:15         ` Linus Torvalds
2019-09-30 16:32           ` Peter Zijlstra
2019-09-30 17:03             ` Linus Torvalds
2019-10-01 10:28           ` David Laight
2019-10-15 21:50             ` Thomas Gleixner
2019-10-01 16:15   ` Ahmed S. Darwish
2019-10-01 16:37     ` Kees Cook
2019-10-01 17:18       ` Ahmed S. Darwish
2019-10-01 17:25     ` Linus Torvalds
2019-10-06 12:07       ` Pavel Machek
2019-10-02 12:01     ` Theodore Y. Ts'o [this message]
2019-10-06 11:41   ` Pavel Machek
2019-10-06 17:26     ` Linus Torvalds
2019-10-06 17:35       ` Pavel Machek
2019-10-06 18:06         ` Linus Torvalds
2019-10-06 18:21           ` Pavel Machek
2019-10-06 18:26             ` Linus Torvalds
2019-10-07 11:47             ` Theodore Y. Ts'o
2019-10-07 22:18               ` Pavel Machek
2019-10-08 11:33                 ` David Laight
2019-10-09  8:02                   ` Pavel Machek
2019-10-09  9:37                     ` David Laight
2019-10-01  2:14 hgntkwis

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