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Re: [TLS] Deprecating Obsolete Key Exchange Methods in TLS

"Blumenthal, Uri - 0553 - MITLL" <uri@ll.mit.edu> Wed, 02 March 2022 17:19 UTC

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From: "Blumenthal, Uri - 0553 - MITLL" <uri@ll.mit.edu>
To: "<tls@ietf.org>" <tls@ietf.org>
CC: Carrick Bartle <cbartle@apple.com>, Nimrod Aviram <nimrod.aviram@gmail.com>
Thread-Topic: [TLS] Deprecating Obsolete Key Exchange Methods in TLS
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Date: Wed, 02 Mar 2022 17:18:56 +0000
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Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/aOsRWeaIojZVHsvb1GJKUyGxsQA>
Subject: Re: [TLS] Deprecating Obsolete Key Exchange Methods in TLS
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Following the discussions around draft-bartle-tls-deprecate-ffdh and draft-aviram-tls-deprecate-obsolete-kex, and after consulting the chairs, we have merged the two drafts into draft-aviram-tls-deprecate-obsolete-kex.

 

The merged draft prescribes the following:

RSA key exchange is a MUST NOT.
 

NIST PQC API is Key Encapsulation – conceptually similar to RSA key exchange.

 

Non-ephemeral finite-field DH is a MUST NOT.
 

Overkill, and unnecessary. Should be SHOULD NOT.

 

Non-ephemeral ECDH is a SHOULD NOT.
 

OK.

 

Ephemeral finite-field DH (DHE) is a MAY, only when fully ephemeral, and only using a well-known group of size at least 2048 bits.
 

Overkill, though requiring sufficiently large group size is fine.

 

 

We added greater justification for point 3 above to address concerns previously raised on the list.

 

We'd love to hear your thoughts.

 

best wishes,

Carrick and Nimrod

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