Re: [TLS] How ALPN makes the http2-tls-relaxed option less secure, compared to NPN (was Re: ALPN concerns)

Martin Thomson <> Mon, 09 December 2013 17:17 UTC

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Date: Mon, 9 Dec 2013 09:16:55 -0800
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From: Martin Thomson <>
To: Brian Smith <>
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Cc: Peter Gutmann <>, "<>" <>
Subject: Re: [TLS] How ALPN makes the http2-tls-relaxed option less secure, compared to NPN (was Re: ALPN concerns)
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On 9 December 2013 05:56, Brian Smith <> wrote:
> Please see
> (read the whole document, but section 2.1 is especially interesting).
> That document defines a mechanism wherein, through protocol
> negotiation, a web browser and server can agree on a "relaxed" form of
> TLS for HTTP where the client does not authenticate the server's
> certificate. The goal is to enable a form of opportunistic encryption
> to HTTP.

My feedback to Mark on this point was that this negotiation was
completely unnecessary.

A server already has a way to signal that it doesn't care about
certain security properties of a resource.  It does that by omitting
the 's' in the resource URL.

A client is then left to decide whether it cares about those
properties.  What requirements are then placed on the subsequent
interactions are up to the client.