Re: [TLS] Encrypting record headers: practical for TLS 1.3 after all?

Eric Rescorla <ekr@rtfm.com> Wed, 02 December 2015 18:02 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Wed, 02 Dec 2015 10:01:42 -0800
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To: "Salz, Rich" <rsalz@akamai.com>
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Subject: Re: [TLS] Encrypting record headers: practical for TLS 1.3 after all?
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On Wed, Dec 2, 2015 at 10:00 AM, Salz, Rich <rsalz@akamai.com> wrote:

> > I think that is false. One could easily use the "cleartext" SNI field
> and insert an encrypted value. A hash of the name would be a simple example
> but not a secure example, of course.
>
> Encrypted SNI doesn't give you the kind of protection you think that it
> does.  We (me and a colleague) did a pretty thorough analysis that showed
> this.  It was not a conclusion we expected, or wanted, to reach.   It was
> presented at the TLS Interim before the IETF in Toronto.  Slides should be
> online.  (For example, the adversary will know the IP address or might not
> care about false positives, etc.)
>
> In spite of this, another colleague (Brian Sniffen) came up with a way to
> do it at the tail end of the Seattle interim.  Encrypt the "true" SNI in
> the semi-static DH key of a "fronting" site.  And then the front decrypts
> the true SNI and forwards to the obscured site. Ekr and dkg presented it in
> Yokohama, but not very well. :)  They're presumably working on something
> better.


Yes, expect an email with a summary of our current thinking in the next
day or so.

-Ekr

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