Re: [TLS] Refactoring client auth/re-key

Karthikeyan Bhargavan <karthik.bhargavan@gmail.com> Sun, 19 October 2014 09:58 UTC

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From: Karthikeyan Bhargavan <karthik.bhargavan@gmail.com>
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Subject: Re: [TLS] Refactoring client auth/re-key
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> Now, for non-PFS key exchanges, certificates can contain exchange keys.
> In practicular, RSA kex server certs do contain exchange key. And
> thus under "hash exchange keys", you need to hash it.

You’re right, including the peer identity applies mainly for non-PFS exchanges where
the peer’s keycard is closely linked to its identity (RSA, PSK, and Fixed DH/ECDH) 
For DHE/ECDHE, if the client/server negotiate a known good group/curve, agreeing
upon the DH params should be enough. Since, by default, the server can choose an
arbitrary group, it seems prudent to include its identity.