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RE: ACTION-319: Split DH Key agreement between new & legacy KDFs

From: Brian LaMacchia <bal@exchange.microsoft.com>
Date: Tue, 14 Jul 2009 12:36:42 +0000
To: Magnus Nyström <magnus@rsa.com>
CC: "public-xmlsec@w3.org" <public-xmlsec@w3.org>
Message-ID: <03703CBF081F9E4CA49CF5FF131362E60D67A1F0@DF-M14-05.exchange.corp.microsoft.com>
Hi Magnus,

I've got no problem changing "new" to "explicit".  I just came up with "new" and "legacy" because I needed something to distinguish the KDF that was in 1.0 from the new KDF format.  I'm certainly not wedded to those two words and have no objection to your proposed edits below.

                                        --bal

-----Original Message-----
From: Magnus Nyström [mailto:magnus@rsa.com]
Sent: Tuesday, July 14, 2009 12:17 PM
To: Brian LaMacchia
Cc: public-xmlsec@w3.org
Subject: Re: ACTION-319: Split DH Key agreement between new & legacy KDFs

Brian, all,

I had a look at this change and would like to make some minor (editorial) suggestions.

Section 5.6.2:

- Replace:

"Use of Diffie-Hellman with "new" KDFs is described in Section 5.6.1.1."

with:

"Use of Diffie-Hellman with explicit KDFs is described in Section 5.6.2.1."

(Note: I have already made the reference correction above; this is about replacing "new" with "explicit")

- Replace:

"However, if implemented, such implementations MUST support the Legacy Key Derviation Function and SHOULD support new Key Derivation Functions."

with:

"However, if implemented, such implementations MUST support the Legacy Key Derivation Function and SHOULD support use of explicit Key Derivation Functions."

Section 5.6.2.1:

- Replace title with:

Diffie-Hellman Key Agreement with explicit Key Derivation Functions

- I agree with you on the example, maybe we could use the ECDH with
   derived keys example in 5.6.4 as a basis?

-- Magnus

On Mon, 6 Jul 2009, Brian LaMacchia wrote:

> Folks,
>
> I've committed revision 1.30 of xmlenc-core-11\Overview.htm, which
> includes text to resolve ACTION-319 for Diffie-Hellman.  Specifically,
> Section 5.6.2, Diffie-Hellman Key Agreement, now has two subsections:
>
> 5.6.2.1. Diffie-Hellman Key Agreement with new Key Derivation
> Functions 5.6.2.2. Diffie-Hellman Key Agreement with Legacy Key
> Derivation Function
>
> 5.6.2.2 has the "legacy KDF" that was defined for DH in XMLENC 1.0, and 5.6.2.1 is for use with the new standard elements for Key Derivation that Magnus introduced.  I made 5.6.2.1 say that it is RECOMMENDED that implementations use a new KDF in the standard format if doing DH, but if you implement DH you're REQUIRED to support the legacy format since it was defined in 1.0.  Also, the best/only way I could come up with to distinguish between legacy and new for DH is to key off the absence or presence of the KA-Nonce element (absence == new, presence == legacy).
>
> I also put a placeholder in Section 5.6.2.1 for an example, since it
> seemed like a good idea to have one there.
Received on Tuesday, 14 July 2009 12:37:25 GMT

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