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From: Eric Biggers <ebiggers@kernel.org>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
	<linux-crypto@vger.kernel.org>,
	linux-fscrypt@vger.kernel.org,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Paul Crowley <paulcrowley@google.com>,
	Greg Kaiser <gkaiser@google.com>,
	Michael Halcrow <mhalcrow@google.com>,
	"Jason A . Donenfeld" <Jason@zx2c4.com>,
	Samuel Neves <samuel.c.p.neves@gmail.com>,
	Tomer Ashur <tomer.ashur@esat.kuleuven.be>
Subject: Re: [RFC PATCH v2 09/12] crypto: nhpoly1305 - add NHPoly1305 support
Date: Mon, 22 Oct 2018 15:40:10 -0700	[thread overview]
Message-ID: <20181022224008.GB59695@gmail.com> (raw)
In-Reply-To: <CAKv+Gu_vXmfNQT8j=G_Zz5C3-zDPPEQ2ne6ZZQw8mD0rifO8qA@mail.gmail.com>

Hi Ard,

On Mon, Oct 22, 2018 at 07:25:27PM -0300, Ard Biesheuvel wrote:
> >
> > Hmm, I'm actually leaning towards the following instead.  Unrolling multiple
> > strides to try to reduce loads of the keys doesn't seem worthwhile in the C
> > implementation; for one, it bloats the code size a lot
> > (412 => 2332 bytes on arm32).
> >
> > static void nh_generic(const u32 *key, const u8 *message, size_t message_len,
> >                        __le64 hash[NH_NUM_PASSES])
> > {
> >         u64 sums[4] = { 0, 0, 0, 0 };
> >
> >         BUILD_BUG_ON(NH_PAIR_STRIDE != 2);
> >         BUILD_BUG_ON(NH_NUM_PASSES != 4);
> >
> >         while (message_len) {
> >                 u32 m0 = get_unaligned_le32(message + 0);
> >                 u32 m1 = get_unaligned_le32(message + 4);
> >                 u32 m2 = get_unaligned_le32(message + 8);
> >                 u32 m3 = get_unaligned_le32(message + 12);
> >
> >                 sums[0] += (u64)(u32)(m0 + key[ 0]) * (u32)(m2 + key[ 2]);
> >                 sums[1] += (u64)(u32)(m0 + key[ 4]) * (u32)(m2 + key[ 6]);
> >                 sums[2] += (u64)(u32)(m0 + key[ 8]) * (u32)(m2 + key[10]);
> >                 sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
> >                 sums[0] += (u64)(u32)(m1 + key[ 1]) * (u32)(m3 + key[ 3]);
> >                 sums[1] += (u64)(u32)(m1 + key[ 5]) * (u32)(m3 + key[ 7]);
> >                 sums[2] += (u64)(u32)(m1 + key[ 9]) * (u32)(m3 + key[11]);
> >                 sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
> 
> Are these (u32) casts really necessary? All the addends are u32 types,
> so I'd expect each (x + y) subexpression to have a u32 type already as
> well. Or am I missing something?
> 

The (u32) casts are only necessary when sizeof(int) > sizeof(u32), as then the
addends will be promoted to 'int'.  Of course, that's never the case for the
Linux kernel.  But I prefer it to be as robust and well-defined as possible,
since people might use this as a reference when coding other implementations,
which could end up finding their way into unusual and/or future platforms.

- Eric

  reply	other threads:[~2018-10-22 22:40 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-15 17:54 [RFC PATCH v2 00/12] crypto: Adiantum support Eric Biggers
2018-10-15 17:54 ` [RFC PATCH v2 01/12] crypto: chacha20-generic - add HChaCha20 library function Eric Biggers
2018-10-19 14:13   ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 02/12] crypto: chacha20-generic - add XChaCha20 support Eric Biggers
2018-10-19 14:24   ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 03/12] crypto: chacha20-generic - refactor to allow varying number of rounds Eric Biggers
2018-10-19 14:25   ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 04/12] crypto: chacha - add XChaCha12 support Eric Biggers
2018-10-19 14:34   ` Ard Biesheuvel
2018-10-19 18:28     ` Eric Biggers
2018-10-15 17:54 ` [RFC PATCH v2 05/12] crypto: arm/chacha20 - add XChaCha20 support Eric Biggers
2018-10-20  2:29   ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 06/12] crypto: arm/chacha20 - refactor to allow varying number of rounds Eric Biggers
2018-10-20  3:35   ` Ard Biesheuvel
2018-10-20  5:26     ` Eric Biggers
2018-10-15 17:54 ` [RFC PATCH v2 07/12] crypto: arm/chacha - add XChaCha12 support Eric Biggers
2018-10-20  3:36   ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 08/12] crypto: poly1305 - add Poly1305 core API Eric Biggers
2018-10-20  3:45   ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 09/12] crypto: nhpoly1305 - add NHPoly1305 support Eric Biggers
2018-10-20  4:00   ` Ard Biesheuvel
2018-10-20  5:38     ` Eric Biggers
2018-10-20 15:06       ` Ard Biesheuvel
2018-10-22 18:42         ` Eric Biggers
2018-10-22 22:25           ` Ard Biesheuvel
2018-10-22 22:40             ` Eric Biggers [this message]
2018-10-22 22:43               ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 10/12] crypto: arm/nhpoly1305 - add NEON-accelerated NHPoly1305 Eric Biggers
2018-10-20  4:12   ` Ard Biesheuvel
2018-10-20  5:51     ` Eric Biggers
2018-10-20 15:00       ` Ard Biesheuvel
2018-10-15 17:54 ` [RFC PATCH v2 11/12] crypto: adiantum - add Adiantum support Eric Biggers
2018-10-20  4:17   ` Ard Biesheuvel
2018-10-20  7:12     ` Eric Biggers
2018-10-23 10:40       ` Ard Biesheuvel
2018-10-24 22:06         ` Eric Biggers
2018-10-30  8:17           ` Herbert Xu
2018-10-15 17:54 ` [RFC PATCH v2 12/12] fscrypt: " Eric Biggers
2018-10-19 15:58 ` [RFC PATCH v2 00/12] crypto: " Jason A. Donenfeld
2018-10-19 18:19   ` Paul Crowley
2018-10-20  3:24     ` Ard Biesheuvel
2018-10-20  5:22       ` Eric Biggers
     [not found]     ` <2395454e-a0dc-408f-4138-9d15ab5f20b8@esat.kuleuven.be>
2018-10-22 11:20       ` Tomer Ashur
2018-10-19 19:04   ` Eric Biggers
2018-10-20 10:26     ` Milan Broz
2018-10-20 13:47       ` Jason A. Donenfeld
2018-11-16 21:52       ` Eric Biggers
2018-11-17 10:29         ` Milan Broz
2018-11-19 19:28           ` Eric Biggers
2018-11-19 20:05             ` Milan Broz
2018-11-19 20:30               ` Jason A. Donenfeld
2018-10-21 22:23     ` Eric Biggers
2018-10-21 22:51       ` Jason A. Donenfeld
2018-10-22 17:17         ` Paul Crowley

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