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Re: [TLS] Version in record MAC

Eric Rescorla <ekr@rtfm.com> Mon, 19 October 2015 18:18 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Mon, 19 Oct 2015 11:17:40 -0700
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To: Martin Thomson <martin.thomson@gmail.com>
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Cc: "tls@ietf.org" <tls@ietf.org>
Subject: Re: [TLS] Version in record MAC
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On Mon, Oct 19, 2015 at 11:13 AM, Martin Thomson <martin.thomson@gmail.com>
wrote:

> On 19 October 2015 at 11:12, Eric Rescorla <ekr@rtfm.com> wrote:
> >
> >
> > On Mon, Oct 19, 2015 at 11:06 AM, Martin Thomson <
> martin.thomson@gmail.com>
> > wrote:
> >>
> >> On 19 October 2015 at 09:28, Eric Rescorla <ekr@rtfm.com> wrote:
> >> >      1. Don't MAC the version at all.
> >> >      2. MAC the negotiated version (which should be clear at
> >> >         this point).
> >>
> >>
> >> 3. Nothing
> >>
> >> The version is implicit in the key derivation (yeah, there are lots of
> >> rounds of HMAC between, but it's there.
> >>
> >> The sequence number is fed into the nonce.
> >
> >
> > How is this different from #1?
>
> #1 implies the sequence number is covered by the MAC.
>

Yeah, I think that's riding the nonce far too hard.

-Ekr

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