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Re: [TLS] Possible blocking of Encrypted SNI extension in China

Rob Sayre <sayrer@gmail.com> Tue, 11 August 2020 05:42 UTC

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From: Rob Sayre <sayrer@gmail.com>
Date: Mon, 10 Aug 2020 22:41:50 -0700
Message-ID: <CAChr6SzzuyB7sxXJQ4gNJwa3iaQcC5jGPE3-sgfY_EkB7DoykA@mail.gmail.com>
To: Peter Gutmann <pgut001@cs.auckland.ac.nz>
Cc: Christian Huitema <huitema@huitema.net>, Christopher Wood <caw@heapingbits.net>, "TLS@ietf.org" <tls@ietf.org>
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Subject: Re: [TLS] Possible blocking of Encrypted SNI extension in China
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On Mon, Aug 10, 2020 at 10:33 PM Peter Gutmann <pgut001@cs.auckland.ac.nz>
wrote:

> Christian Huitema <huitema@huitema.net> writes:
>
> >Fingerprinting is a real issue but from the reports, this is not what is
> >happening here.
>
> Sure, I was just pointing out that they're using the brute-force approach
> now
> but presumably at some point will stop blocking when they've implemented a
> way
> to bypass it.  My guess is that since the GFW uses blocklisting (of known
> sites/pages) all they'll need to do is fingerprint the sites they want to
> block and take it from there.
>

Do you think this fingerprinting will work with the newer ECH design, if
the client can add arbitrary content to the encrypted payload?

Another technique to use here: deploy servers that refuse unencrypted
ClientHello messages.

thanks,
Rob

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