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Re: [TLS] issues with DTLS + PSK

Martin Thomson <martin.thomson@gmail.com> Mon, 05 January 2015 17:42 UTC

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Date: Mon, 05 Jan 2015 09:42:55 -0800
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From: Martin Thomson <martin.thomson@gmail.com>
To: Nikos Mavrogiannopoulos <nmav@redhat.com>
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Cc: IETF TLS <tls@ietf.org>
Subject: Re: [TLS] issues with DTLS + PSK
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On 5 January 2015 at 08:08, Nikos Mavrogiannopoulos <nmav@redhat.com> wrote:
> A solution would be, on a revision of the PSK ciphersuites, to define
> PSK ciphersuites which will authenticate (e.g., with a MAC), an (EC)DH
> key exchange. That would allow a graceful failure in case of a mismatch
> of keys. In addition it will allow the usage of hardware security
> modules with PSK (something that is very hard to impossible with the
> current ECDHE/DHE PSK ciphersuites).

If the same general formulation we've been using for TLS 1.3 is
consistently applied to PSK, then key derivation will be based on the
(EC)DH exchange and the PSK will only be used to authenticate, exactly
as you describe.  I think that would be a pretty good answer.

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