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Re: [MLS] Key confirmation - Extra MAC needed?

"Katriel Cohn-Gordon" <me@katriel.co.uk> Tue, 23 October 2018 15:22 UTC

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From: Katriel Cohn-Gordon <me@katriel.co.uk>
To: Richard Barnes <rlb@ipv.sx>
Cc: mls@ietf.org
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Date: Tue, 23 Oct 2018 16:22:26 +0100
Archived-At: <https://mailarchive.ietf.org/arch/msg/mls/e9WwmYe47mzxHDqTMYFfVphDPI0>
Subject: Re: [MLS] Key confirmation - Extra MAC needed?
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"Publish a MAC with a secret key" seems like a safe-ish operation
in general.
"Publish a secret key from the key schedule" seems like a dangerous
operation in general.
The fact that the key schedule happens to derive keys in a sensible
enough way that publishing one key doesn't affect security of the others
is a very good feature, but in my head it seems a bit funny to conclude
that it's safe to publish keys. IOW, the cleanness I am thinking of is
the separation between how the key schedule works and what the protocol
does with the derived keys.
k

On Tue, 23 Oct 2018, at 4:14 PM, Richard Barnes wrote:
> Can you say more about how MAC'ing over "" makes things cleaner?

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