Re: [TLS] Industry Concerns about TLS 1.3

Thijs van Dijk <schnabbel@inurbanus.nl> Fri, 23 September 2016 07:35 UTC

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From: Thijs van Dijk <schnabbel@inurbanus.nl>
Date: Fri, 23 Sep 2016 09:35:27 +0200
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To: =?UTF-8?Q?Colm_MacC=C3=A1rthaigh?= <colm@allcosts.net>
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Subject: Re: [TLS] Industry Concerns about TLS 1.3
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On 23 September 2016 at 04:04, Colm MacCárthaigh <colm@allcosts.net>; wrote:

> If the problem is the use of forward secrecy then there is a simple
>>>> solution, don't use it.
>>>> That is, you can, as a server, have a fixed key_share for which the
>>>> secret exponent becomes the private key exactly as in the RSA case. It does
>>>> require some careful analysis, though.
>>>>
>>>
>> The key_share contributed by the client is indeed ephemeral and it
>> replaces the random key chosen by the client in the RSA-based scheme.
>>
>
> Yep, you're right, now I get it. I also now wonder if clients should make
> a best effort of detecting duplicate parameters and rejecting them.
>

Regular clients, no.
But this would be a useful addition to debugging / scanning suites (e.g.
Qualys), or browser extensions for the security conscious (e.g. CertPatrol).

-Thijs