Re: [PATCH v2 3/6] crypto: lib/sha256 - Clear W[] in sha256_update() instead of sha256_transform()

Eric Biggers
2020-10-22T04:59:53Z

On Tue, Oct 20, 2020 at 04:39:54PM -0400, Arvind Sankar wrote:
> The temporary W[] array is currently zeroed out once every call to
> sha256_transform(), i.e. once every 64 bytes of input data. Moving it to
> sha256_update() instead so that it is cleared only once per update can
> save about 2-3% of the total time taken to compute the digest, with a
> reasonable memset() implementation, and considerably more (~20%) with a
> bad one (eg the x86 purgatory currently uses a memset() coded in C).
>
> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>

Looks good,

Reviewed-by: Eric Biggers <ebiggers@google.com>