Re: [TLS] About encrypting SNI

"Sniffen, Brian" <bsniffen@akamai.com> Thu, 17 April 2014 20:26 UTC

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From: "Sniffen, Brian" <bsniffen@akamai.com>
To: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 17 Apr 2014 16:26:35 -0400
Thread-Topic: [TLS] About encrypting SNI
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Cc: "tls@ietf.org" <tls@ietf.org>, Andy Lutomirski <luto@amacapital.net>
Subject: Re: [TLS] About encrypting SNI
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On Apr 17, 2014, at 3:20 PM, "Eric Rescorla" <ekr@rtfm.com> wrote:
> 
> One concern I would have is whether we understand the problem well
> enough to actually specify this. I'm not an expert in this area, but weren't
> there a bunch of concerns about designing puzzles that were effective
> without being prohibitively expensive for mobile devices?

Oh, I expect to deny service to users whose computational power is swamped by an adversary node's. I don't have a way to fix that. But conventional puzzles are enough to convert an adversary who could deny service to everybody---by overloading the server---to one who can only deny service to computationally weak clients, or when they overwhelmingly outnumber normal clients. 

And if we ever do come to terms on session resumption, that can help mobile clients a good bit. I understand most mobile clients keep sessions in persistent storage to keep them alive as long as possible for this reason.