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Date: Wed, 11 Oct 2017 14:29:09 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: "Tobin C. Harding" <me@...in.cc>, 
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, KVM list <kvm@...r.kernel.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Kees Cook <keescook@...omium.org>, 
	Paolo Bonzini <pbonzini@...hat.com>, Tycho Andersen <tycho@...ker.com>, 
	"Roberts, William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, 
	Jordan Glover <Golden_Miller83@...tonmail.ch>, Greg KH <gregkh@...uxfoundation.org>, 
	Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>, Ian Campbell <ijc@...lion.org.uk>, 
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will.deacon@....com>, Steven Rostedt <rostedt@...dmis.org>, 
	Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>, 
	Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>
Subject: Re: [PATCH 0/3] add %pX specifier

On Wed, Oct 11, 2017 at 1:11 PM, Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> Indeed the correct functions to use would be siphash_1u32 or
> siphash_1u64, depending. Depending on the popularity of that, we might
> even consider making a siphash_1ulong helper, I suppose.

Yeah, siphash is probably the sanest thing to use.

How bad would it be to use HalfSipHash on 32-bit architectures?

On a 32-bit machine, the full siphash is pretty expensive - big
constants, and lots of 64-bit shifts. And 32-bit machines also tend to
mean "slow machines" these days.

I suspect there's little point in worrying a ton about the 64-bit key,
considering that I think the *input* is generally more guessable than
the output or the key.

           Linus

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