Re: [PATCH v2 2/2] crypto: arm64/ghash - add NEON accelerated fallback for 64-bit PMULL

On 18 July 2017 at 10:49, Herbert Xu [off-list ref] wrote:

On Wed, Jul 05, 2017 at 12:43:19AM +0100, Ard Biesheuvel wrote:

quoted

Implement a NEON fallback for systems that do support NEON but have
no support for the optional 64x64->128 polynomial multiplication
instruction that is part of the ARMv8 Crypto Extensions. It is based
on the paper "Fast Software Polynomial Multiplication on ARM Processors
Using the NEON Engine" by Danilo Camara, Conrado Gouvea, Julio Lopez and
Ricardo Dahab (https://hal.inria.fr/hal-01506572), but has been reworked
extensively for the AArch64 ISA.

On a low-end core such as the Cortex-A53 found in the Raspberry Pi3, the
NEON based implementation is 4x faster than the table based one, and
is time invariant as well, making it less vulnerable to timing attacks.
When combined with the bit-sliced NEON implementation of AES-CTR, the
AES-GCM performance increases by ~2x (from 58 to 30 cycles per byte).

Signed-off-by: Ard Biesheuvel <redacted>

This patch does not apply against cryptodev.

Yeah, it implements a non-SIMD fallback which depends on the AES
refactor series.