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In-Reply-To: <79bb1e11-6176-6341-11f8-6bf32ed9f286@huitema.net>
From: Ben Schwartz <bemasc@google.com>
Date: Tue, 2 Jun 2020 17:26:02 -0400
Message-ID: <CAHbrMsA9dSsCki=zGkCKmx4690eaLvFsU7=UMTWiNHopkdT3xA@mail.gmail.com>
To: Christian Huitema <huitema@huitema.net>
Cc: "Salz, Rich" <rsalz@akamai.com>,
 Stephen Farrell <stephen.farrell@cs.tcd.ie>, 
 Christopher Wood <caw@heapingbits.net>, "TLS@ietf.org" <tls@ietf.org>
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/-oulFyx99eQ5i8GTVyJGIP5Ns5g>
Subject: Re: [TLS] I-D Action: draft-ietf-tls-esni-07.txt
Precedence: list

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On Tue, Jun 2, 2020 at 4:50 PM Christian Huitema <huitema@huitema.net>
wrote:

> On 6/2/2020 11:44 AM, Salz, Rich wrote:
>
> > Trial description scares me.  Perhaps that's not a rationale fear -- one
> of the points of CDN support is a large anonymity set -- but I worry about
> the DoS possibilities. Especially if QUIC picks this up (now trivial to
> fake "client IP") and if some large mobile manufacturers move to use this
> as the default as I've heard they are considering.
>
> I am looking at a very specific use case: mobile servers.


Presumably, connecting to a mobile server requires a rendezvous (a.k.a.
"signalling") channel, in order to learn its current IP address.


> Suppose that
> you use TLS to connect from a mobile client to a mobile server using an
> untrusted network, such as a Wi-Fi network in an airport. Neither the
> client not the server want to reveal their identity when using the
> network. When using TLS, they will use ECH to hide finger-printable data
> such as SNI, ALPN, or QUIC initial parameters. But the record digest in
> the ECH blob is also an unique identifier of the server.


For your use case, if the server's IP address is dynamic, and discovered
through a rendezvous channel, can its ECH blob also be dynamic, and
discovered through the same channel?

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Tue, Jun 2, 2020 at 4:50 PM Christ=
ian Huitema &lt;<a href=3D"mailto:huitema@huitema.net">huitema@huitema.net<=
/a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0=
px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">O=
n 6/2/2020 11:44 AM, Salz, Rich wrote:<br>
<br>
&gt; Trial description scares me.=C2=A0 Perhaps that&#39;s not a rationale =
fear -- one of the points of CDN support is a large anonymity set -- but I =
worry about the DoS possibilities. Especially if QUIC picks this up (now tr=
ivial to fake &quot;client IP&quot;) and if some large mobile manufacturers=
 move to use this as the default as I&#39;ve heard they are considering.<br=
>
<br>
I am looking at a very specific use case: mobile servers.</blockquote><div>=
<br></div><div>Presumably, connecting to a mobile server requires a rendezv=
ous (a.k.a. &quot;signalling&quot;) channel, in order to learn its current =
IP address.</div><div>=C2=A0</div><blockquote class=3D"gmail_quote" style=
=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding=
-left:1ex"> Suppose that<br>
you use TLS to connect from a mobile client to a mobile server using an<br>
untrusted network, such as a Wi-Fi network in an airport. Neither the<br>
client not the server want to reveal their identity when using the<br>
network. When using TLS, they will use ECH to hide finger-printable data<br=
>
such as SNI, ALPN, or QUIC initial parameters. But the record digest in<br>
the ECH blob is also an unique identifier of the server.</blockquote><div><=
br></div><div>For your use case, if the server&#39;s IP address is dynamic,=
 and discovered through a rendezvous channel, can its ECH blob also be dyna=
mic, and discovered through the same channel?</div></div></div>

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