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Re: [openscreenprotocol] Describes how TLS and certificates are used by agents. (#212)

From: nigelcearnshaw via GitHub <sysbot+gh@w3.org>
Date: Fri, 13 Sep 2019 11:12:40 +0000
To: public-webscreens@w3.org
Message-ID: <issue_comment.created-531197493-1568373158-sysbot+gh@w3.org>
A comment on key_share TLS extension.
"The key_share extension must be set to the cryptographic parameters for the negotiated signature algoirithm"

Note that Key_share is associated with the group and public keys by which the parties derive their shared keys for traffic encryption etc, not the signature public keys (which are in the certificates)

This seems to be  saying that both the signature and DH key exchange parameters must use the same groups? I can't see why that should be the case. Even if they were, the ephemeral keys should be fresh.

More typically this should be (from rfc8446)

The key_share extension must be set to the cryptographic parameters. 

We could more helpfully say

The key_share extension must be set to the cryptographic parameters for the TLS key exchange as per RFC 8446 Section 4.2.8 consistent with the supported_groups extension.



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Received on Friday, 13 September 2019 11:12:41 UTC

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