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

Stefan Metzmacher metze at
Wed Nov 22 21:05:08 UTC 2023

Am 22.11.23 um 21:26 schrieb Andrew Bartlett via samba-technical:
> On Wed, 2023-11-22 at 12:07 +0100, Andreas Schneider wrote:
>> 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
>>> 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 (
>>>   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.
> The main issue is the time to get the changes into the distributions so
> we can get them into master, but yes, it has been an awesome
> collaboration.
>> They implemented all the features we needed for Samba so far.
>> Example:
>> They also fixed performance issues we discovered ...
> Thanks.  It looks like we won't need the DH stuff, thankfully, but we
> might need an alternate key derivation function: SP800-108.

Isn't that what have in smb2_key_derivation()?


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