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Re: [Lurk] WG Call for adoption of draft-rescorla-tls-subcerts

"Fossati, Thomas (Nokia - GB/Cambridge, UK)" <thomas.fossati@nokia.com> Sat, 22 April 2017 20:45 UTC

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From: "Fossati, Thomas (Nokia - GB/Cambridge, UK)" <thomas.fossati@nokia.com>
To: Sean Turner <sean@sn3rd.com>, "<tls@ietf.org>" <tls@ietf.org>
CC: "lurk@ietf.org" <lurk@ietf.org>, "Fossati, Thomas (Nokia - GB/Cambridge, UK)" <thomas.fossati@nokia.com>
Thread-Topic: [Lurk] WG Call for adoption of draft-rescorla-tls-subcerts
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Date: Sat, 22 Apr 2017 20:45:47 +0000
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Subject: Re: [Lurk] WG Call for adoption of draft-rescorla-tls-subcerts
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I've read draft-rescorla-tls-subcerts-01 and have a few comments.

It's a well written document and the low-level mechanics look ok.  However,
I think I have a couple of issues with the overall design.

First: it is not self-sufficient.  The fact that clients must opt-in implies
that servers must have a backup plan.  Since keeping the high-value key
material in the same node as the delegate credentials contradicts the basic
security goal, the only realistic fallback is to have a key-server / LURK box
at hand?  But this has the known and already discussed limitations --
complicated setup and operations, scaling issues, single point of failure,
etc. -- which make it inapplicable to some key use cases (CDN).

Second, we need to change the stack at the endpoints.  This might be OK for
browsers, but it's a bit more problematic when the UA is an STB or a
residential gateway, as these things tend to have much slower release and
upgrade cycles.

With regards to WG adoption, I guess I'm neutral.  I think it doesn't hurt
to have something like this, but for the reasons stated above, I'm not sure
it provides a solution to the LURK problem.

Cheers, t

PS: It'd be nice if the document discussed the implication of the "unregulated"
delegation mechanism especially with regards to its auditability.

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