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Re: [TLS] Final nail in the coffin for cleartext SNI/ALPN in TLS 1.3

Geoffrey Keating <geoffk@geoffk.org> Thu, 28 November 2013 21:56 UTC

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To: Ralf Skyper Kaiser <skyper@thc.org>
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From: Geoffrey Keating <geoffk@geoffk.org>
Date: Thu, 28 Nov 2013 13:56:24 -0800
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Subject: Re: [TLS] Final nail in the coffin for cleartext SNI/ALPN in TLS 1.3
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Ralf Skyper Kaiser <skyper@thc.org> writes:

> "HTTP keepalives and session resumption mean that most requests do
> not require a full handshake, so handshake operations do not
> dominate our CPU usage."
> 
> This is great news for encrypted SNI and ALPN.

To take advantage of this, a server using encrypted SNI and/or ALPN
must be able to determine the SNI/ALPN information from the session
resumption data.  I guess this is not too much of a problem, since the
usual reason you can't do this is that you have some kind of front-end
'server NAT' or load balancer which redirects connections to back-end
servers based on SNI/ALPN without doing any cryptography, and this
would be impossible with encrypted SNI/ALPN anyway.

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