Suggested crypto libs for Diffie-Hellman and Eliptic Curve Diffie-Hellman

[Andreas Schneider]

On Thursday, 16 November 2023 07:08:59 CET Andrew Bartlett via samba-technical 
wrote:
> For Group Managed service accounts, which we are working on, for
> reasons around RODCs and a few other things, Microsoft has decided to
> internally use a key-agreement between a 'root key' and a 'service
> key', both held in AD.
> 
> The password comes, as I understand it, from the key agreement derived
> out of a Diffie-Hellman or Eliptic Curve Diffie-Hellman exchanges.
> 
> This is all in MS-GKDI, referenced from
> https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-adts/9cd2fc
> 5e-7305-4fb8-b233-2a60bc3eec68
> 
> I just wanted to check if there are particularly cryptographic
> libraries we should consider for this work.
> 
> In the past we have looked to libnettle when gnutls didn't provide the
> functions we wanted, but that was backed out fairly fast as another
> method was found (https://bugzilla.samba.org/show_bug.cgi?id=13276 0784
> 4a9a13506b4ca9181cfde05d9e4170208f88).
> 
> Even so, for this case is libnettle still the best first place to look?

If something is missing in GnuTLS you need, open tickets at GnuTLS. They are 
fairly quick implementing the stuff we need.

They implemented all the features we needed for Samba so far. Example:

https://gitlab.com/gnutls/gnutls/-/merge_requests/1611/

Also AES-GMAC, AES-CCM, AES-CBF8 ...

They also fixed performance issues we discovered ...


Best regards


	Andreas


-- 
Andreas Schneider                      asn at samba.org
Samba Team                             www.samba.org
GPG-ID:     8DFF53E18F2ABC8D8F3C92237EE0FC4DCC014E3D