[PATCH 42/43] Introduce negotiation for Diffie--Hellman groups.

Mark Wooding mdw at distorted.org.uk
Mon May 1 02:26:43 BST 2017

Ian Jackson <ijackson at chiark.greenend.org.uk> writes:

> EXPLICIT does not need to be early.  The new dh bits (apart from the
> trad Zp one) need to be early.  EXPLICIT should not be early, so that
> a new secnet can be configured to be compatible with ones that predate
> the capability machinery (by telling it not to advertise new dh
> groups).

EXPLICIT and TRADZP need to be early /if/ they're accompanying
non-default DH group caps.  The caps sent in MSG1 are the early caps and
anything else that may be convenient.  But, for correct DH-group
negotiation, if I'm sending a non-default group, I /must/ also send
EXPLICIT, and -- if it's a group I permit -- TRADZP.  So those bits are
early in this context.

More in the ECDH etc. thread.

-- [mdw]

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