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Re: [TLS] ECDH_anon

"Blumenthal, Uri - 0553 - MITLL" <uri@ll.mit.edu> Wed, 27 January 2016 17:57 UTC

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From: "Blumenthal, Uri - 0553 - MITLL" <uri@ll.mit.edu>
To: Martin Thomson <martin.thomson@gmail.com>
Thread-Topic: [TLS] ECDH_anon
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Date: Wed, 27 Jan 2016 17:57:47 +0000
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Subject: Re: [TLS] ECDH_anon
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On 1/27/16, 12:47 , "Martin Thomson" <martin.thomson@gmail.com> wrote:

>On 28 January 2016 at 02:17, Blumenthal, Uri - 0553 - MITLL
><uri@ll.mit.edu> wrote:
>> Anon  ‎!= Ephemeral, despite some similarities.
>
>From a protocol perspective, they are the same.

If you mean that you cannot distinguish between the two on the wire - I
agree.

>The distinction at the protocol level between ECDH_RSA (for example) and
>ECDH_anon is
>that ECDH_anon requires a ServerKeyShare message in the same way that
>ECDHE_RSA does.

The distinction is in what you can do with the exchange.

>I agree that Nikos' point is a good one, but we've implementations of
>ECDHE_ that provide a stable value for their ephemeral key
>(unfortunately, that's the default mode in NSS).

But that is BAD (and it’s gotta change ;). It’s like implementations that
always generate random number “0” (no smileys - I’ve seen those).

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