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Re: [TLS] HKDF

Ilari Liusvaara <ilari.liusvaara@elisanet.fi> Thu, 26 March 2015 16:44 UTC

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Date: Thu, 26 Mar 2015 18:44:27 +0200
From: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
To: Michael StJohns <msj@nthpermutation.com>
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Subject: Re: [TLS] HKDF
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On Thu, Mar 26, 2015 at 10:55:48AM -0400, Michael StJohns wrote:
> On 3/26/2015 3:24 AM, Ilari Liusvaara wrote:
> >Turns out you can't even implement TLS fully in design that does not
> >know about TLS,
> 
> This is true for TLS1.2 and before, mainly because of the master secret
> expansion and the PRF.  Everything else is bog standard crypto.
> 
> >nor does it seem one can even change TLS so that
> >would be possible (at least without introducing gaping security holes).
> 
> I don't know that I believe that.  TLS is a protocol wrapped around a set of
> cryptographic constructs.  There are ways to use standard constructs in TLS
> to build a secure protocol.   It will require some surgery on TLS1.2, but I
> think that's well underway.

The problem is that TLS includes values that are potentially:

- Exportable
- Channel Binding
- Secret

All at the same time. Such value needs to chain to MS, and is exportable.


-Ilari

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