[gnutls-help] ECDH internal functions and FIPS140-2 mode

[Daiki Ueno]

Hello,

Nicolas Mora <nicolas at babelouest.org> writes:

> I'd like to use ECDH key agreement with GnuTLS. As far as I can see,
> there is no public function to generate a shared secret with ECC keys.

I think this is a long wanted feature:
https://gitlab.com/gnutls/gnutls/-/issues/894

> In lib/nettle/pk.c [1], the ECDH functions are defined if
> ENABLE_FIPS140 is defined.
>
> According to thee documentation [2], FIPS140-2 mode is not available
> without adding configure option –enable-fips140-mode.
>
> In an old message on this ML [3], it was offered these functions to be
> exported in the normal API, but this message wasn't answered, and the
> ecdh functions are still private and available only with FIPS140-2
> mode.
>
> I'd like to make a feature request for the ECDH functions to be
> available in the normal API, even in non FIPS140-2 mode. Would it be
> possible in a future version?

Yes, that would be very useful.  What I am concerned with this is how it
would affect FIPS140-2 validation.  Once they become part of the public
API, we may need to add checks to meet the SP800-56A requirements when
they are called under FIPS140-2 mode.  Having said that, I guess the
implementation of such checks wouldn't be that hard.  Stephan (Cc'ed)
might have some opinion on that.

Regards,
-- 
Daiki Ueno