Re: [TLS] I-D Action: draft-ietf-tls-curve25519-00.txt

Eric Rescorla <ekr@rtfm.com> Fri, 12 June 2015 20:05 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Fri, 12 Jun 2015 16:04:48 -0400
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To: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
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Subject: Re: [TLS] I-D Action: draft-ietf-tls-curve25519-00.txt
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On Fri, Jun 12, 2015 at 3:56 PM, Ilari Liusvaara <
ilari.liusvaara@elisanet.fi> wrote:

> On Fri, Jun 12, 2015 at 11:02:30AM -0700, internet-drafts@ietf.org wrote:
> >       Filename        : draft-ietf-tls-curve25519-00.txt
>
> "Servers MUST NOT select an ECDHE_ECDSA ciphersuite if there are no
> common curves suitable for ECDSA."
>
> You mean MUST NOT select ECDSA certificate? Because TLS 1.2 rules
> seemingly allow selecting ECDHE_RSA ciphersuite with ECDSA
> certificate.
>
> "This section defines a new point format suitable to encode Curve25519
> public keys, as well as an identifier to negotiate this new format in
> TLS, and includes guidance on their use."
>
> Is this format going to be the chosen one for TLS 1.3? Because TLS 1.3
> can't negotiate point formats for ECDHE.
>
> Also, I don't see the value of trying to negotiate the point format,
> and I think that the negotiation will act as an implementation error
> source.


I would suggest claiming that this point format is "uncompressed" and the
only point format for Curve25519.

-Ekr


>
> -Ilari
>
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