Re: [TLS] TLS@IETF101 Agenda Posted

Russ Housley <housley@vigilsec.com> Tue, 13 March 2018 22:28 UTC

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From: Russ Housley <housley@vigilsec.com>
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Date: Tue, 13 Mar 2018 18:28:09 -0400
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To: Andrei Popov <Andrei.Popov@microsoft.com>
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Subject: Re: [TLS] TLS@IETF101 Agenda Posted
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> On Mar 13, 2018, at 6:21 PM, Andrei Popov <Andrei.Popov@microsoft.com>; wrote:
> 
> If the client were to exclusively offer DHE-based ciphersuites, then the visibility techniques that have been used in the past are thwarted.
> TLS1.3-visibility will be equally thwarted if the client does not send the empty “tls_visibility” extension, right?
> (Assuming the server chooses to play by the rules, of course.)

Two points:

1) Yes, the server cannot use the "tls_visibility" extension unless the client offers it.  This is to enable client opt-in.

2) If the server sends the "tls_visibility" extension without the client first offering it, by the normal TLS extension processing rules, the client MUST close the connection.

Russ