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Date: Fri, 16 Dec 2016 22:15:23 +0100
From: Hannes Frederic Sowa <hannes@...essinduktion.org>
To: "Jason A. Donenfeld" <Jason@...c4.com>,
 kernel-hardening@...ts.openwall.com, "Theodore Ts'o" <tytso@....edu>,
 George Spelvin <linux@...encehorizons.net>,
 Andi Kleen <ak@...ux.intel.com>, David Miller <davem@...emloft.net>,
 David Laight <David.Laight@...lab.com>,
 "Daniel J . Bernstein" <djb@...yp.to>,
 Eric Biggers <ebiggers3@...il.com>,
 "Jean-Philippe Aumasson" <jeanphilippe.aumasson@...il.com>,
 Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>,
 Andy Lutomirski <luto@...capital.net>, Netdev <netdev@...r.kernel.org>,
 Tom Herbert <tom@...bertland.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Vegard Nossum <vegard.nossum@...il.com>
Subject: Re: Re: [PATCH v5 1/4] siphash: add cryptographically
 secure PRF

On Fri, Dec 16, 2016, at 22:01, Jason A. Donenfeld wrote:
> Yes, on x86-64. But on i386 chacha20 incurs nearly the same kind of
> slowdown as siphash, so I expect the comparison to be more or less
> equal. There's another thing I really didn't like about your chacha20
> approach which is that it uses the /dev/urandom pool, which means
> various things need to kick in in the background to refill this.
> Additionally, having to refill the buffered chacha output every 32 or
> so longs isn't nice. These things together make for inconsistent and
> hard to understand general operating system performance, because
> get_random_long is called at every process startup for ASLR. So, in
> the end, I believe there's another reason for going with the siphash
> approach: deterministic performance.

*Hust*, so from where do you generate your key for siphash if called
early from ASLR?

Bye,
Hannes

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