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Re: [TLS] Encrypt content type (#51) + Remove TLSCiphertext.version (#144)

Dave Garrett <davemgarrett@gmail.com> Sun, 17 May 2015 01:04 UTC

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From: Dave Garrett <davemgarrett@gmail.com>
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Date: Sat, 16 May 2015 21:04:28 -0400
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Subject: Re: [TLS] Encrypt content type (#51) + Remove TLSCiphertext.version (#144)
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On Saturday, May 16, 2015 08:23:19 pm Eric Rescorla wrote:
> On Sat, May 16, 2015 at 4:54 PM, Dave Garrett <davemgarrett@gmail.com>
> wrote:
> > Is there enough agreement on list for consensus on:
> > https://github.com/tlswg/tls13-spec/pull/51/files
> > &
> > https://github.com/tlswg/tls13-spec/issues/144
> > ?
> >
> > This would get us to the point of no AD for AEAD, as noted by Martin
> > Thomson.
> > https://www.ietf.org/mail-archive/web/tls/current/msg15490.html
> 
> No. I believe that the present consensus is to retain the existing version
> bytes in place but just leave them fixed.

To be clear, the proposal would be to drop TLSCiphertext.version, but NOT
TLSPlaintext.version. The latter needs to stay in place for compatibility,
but the former is after version negotiation and provides no useful info. Just a
waste of 2 bytes for every record at that point. The version number is
currently in the context string for the certificate verification signatures, and
Martin suggested mixing it into the PRF/HKDF info string to make the keying
material dependent on the version number. (see quoted mailing list URL)


Dave

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