Re: [TLS] Certificate keyUsage enforcement question (new in RFC8446 Appendix E.8)

Peter Gutmann <pgut001@cs.auckland.ac.nz> Thu, 08 November 2018 22:27 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: "Blumenthal, Uri - 0553 - MITLL" <uri@ll.mit.edu>, "<tls@ietf.org>" <tls@ietf.org>
Thread-Topic: [TLS] Certificate keyUsage enforcement question (new in RFC8446 Appendix E.8)
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Date: Thu, 8 Nov 2018 22:27:24 +0000
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Subject: Re: [TLS] Certificate keyUsage enforcement question (new in RFC8446 Appendix E.8)
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Blumenthal, Uri - 0553 - MITLL <uri@ll.mit.edu> writes:

>Always enforce peer certificate key usage (separation) for ECDSA. ECDSA keys
>are more brittle when misused.

Since ECDSA can only do signing, isn't this a bit redundant?  In other words
you can't really not enforce keyUsage for a signature-only algorithm.

Peter.