Re: [TLS] A la carte handshake negotiation

Dave Garrett <> Wed, 17 June 2015 04:42 UTC

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From: Dave Garrett <>
To: Nico Williams <>
Date: Wed, 17 Jun 2015 00:41:30 -0400
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Subject: Re: [TLS] A la carte handshake negotiation
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On Tuesday, June 16, 2015 11:59:52 pm Nico Williams wrote:
> PSK with a fixed key is a pointless complexity.  We already have an
> unauthenticated mode; there's no need to replace it with another more
> complicated one.
> > deprecate these suites is that this feature is under-maintained in the
> > spec. There are currently no ECDHE AEAD anon suites. [...]
> We've noted this and asked for them to be registered.  The missing
> assignments does not mean that the feature is unmaintained as
> implemented (it's in use), as as to the spec: we're maintaining it now,
> and a la carte negotiation effectively fixes the missing cipher suite
> assignment issue.

I'm trying to reduce the number of valid prefixes. The anon options are essentially:

1) Merge (EC)DH_anon into ECDHE_PSK & drop all (EC)DH_anon
2) Define all ECDHE_anon & drop all DH_anon

I moved towards #1 in the last revision of the draft because some seemed interested in dropping the feature to reduce overall spec complexity. There's notable disagreement on this list over whether or not the anon suites are worthwhile, so I wrote up what would be needed for it. (e.g. wasn't sure if ChaChaPoly would get an anon assignment)

> Why do even that?

The idea was to get rid of an entire class of suites as a simplification. There seemed to be a desire on list for dropping them. (was brought up by a few)

I think I'll set the anon deprecation part aside and go back to #2, if defining the new suites isn't an issue. I still think they should be actively discouraged in favor of trust on first use.

I'll change the WIP in a bit.