Re: [TLS] Privacy considerations - identity hiding from eavesdropping in (D)TLS

Viktor Dukhovni <ietf-dane@dukhovni.org> Tue, 25 August 2015 01:19 UTC

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Date: Tue, 25 Aug 2015 01:19:14 +0000
From: Viktor Dukhovni <ietf-dane@dukhovni.org>
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Subject: Re: [TLS] Privacy considerations - identity hiding from eavesdropping in (D)TLS
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On Mon, Aug 24, 2015 at 05:33:18PM -0400, Paul Wouters wrote:

> On Mon, 24 Aug 2015, Eric Rescorla wrote:
> 
> >TLS 1.3 encrypts both the client's and server's certificates already.
> >The server's certificate is secure only against passive attack.
> 
> Not having read the TLS 1.3 draft, in IKE parties can send a hash of the
> CAs they trust, so unless you receive a hash of a known CA to you, you
> can withold your own certificate from being sent.
> 
> Is a similar mechanism not planned for TLS 1.3?

This would break DANE, unless the mechanism also allowed the client
to send a TLSA RRset instead, with the server then needing code to
figure out which chains match which TLSA RRs.  This is I think too
complex.  

If the client is willing to live without any certificate at all,
it can include anon-(EC)DH ciphersuites in its cipherlist at a
higher preference than any ciphersuites that use certificates..
Otherwise, the server sends a suitable chain per SNI and
closest match to supported signature algorithms.

-- 
	Viktor.