Re: [PATCH v5 0/4] Implement GCM ghash using Zbc and Zbkb extensions

[Eric Biggers]

Hi Heiko,

On Mon, Jun 12, 2023 at 11:04:38PM +0200, Heiko Stuebner wrote:
> From: Heiko Stuebner <heiko.stuebner@xxxxxxxx>
> 
> This was originally part of my vector crypto series, but was part
> of a separate openssl merge request implementing GCM ghash as using
> non-vector extensions.
> 
> As that pull-request
>     https://github.com/openssl/openssl/pull/20078
> got merged recently into openssl, we could also check if this could
> go into the kernel as well and provide a base for further accelerated
> cryptographic support.

I'm still a bit skeptical of the usefulness of a standalone "ghash"
implementation, when in practice it will only be used as part of "gcm(aes)".
Directly implementing "gcm(aes)" (instead of relying on crypto/gcm.c to compose
"ghash" and "ctr(aes)") also allows some performance optimizations.

I asked about this on v4
(https://lore.kernel.org/linux-crypto/ZCSG71bRuTzVutdm@xxxxxxxxx/),
but I didn't receive a response.

Any thoughts on this?

- Eric