linux-kernel - Re: x86/random: Speculation to the rescue

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Message-ID: <20191002120115.GA13880@mit.edu>
Date:   Wed, 2 Oct 2019 08:01:15 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     "Ahmed S. Darwish" <darwish.07@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>, a.darwish@...utronix.de,
        LKML <linux-kernel@...r.kernel.org>,
        Nicholas Mc Guire <hofrat@...ntech.at>,
        the arch/x86 maintainers <x86@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: x86/random: Speculation to the rescue

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