Re: [TLS] draft-ietf-tls-curve25519-01: Is public key validation necessary or helpful?

Eric Rescorla <ekr@rtfm.com> Thu, 31 December 2015 20:55 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 31 Dec 2015 12:55:09 -0800
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To: Ilari Liusvaara <ilariliusvaara@welho.com>
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Subject: Re: [TLS] draft-ietf-tls-curve25519-01: Is public key validation necessary or helpful?
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On Thu, Dec 31, 2015 at 12:49 PM, Ilari Liusvaara <ilariliusvaara@welho.com>
wrote:

> On Thu, Dec 31, 2015 at 12:23:50PM -0800, Eric Rescorla wrote:
> > On Thu, Dec 31, 2015 at 12:20 PM, Ilari Liusvaara <
> ilariliusvaara@welho.com>
> > wrote:
> >
> > 2. Implementations which only do new algorithms can mandate EMS and not
> > implement old derivation at all, provided we make that a rule here.
>
> Well, the EMS spec already says that endpoints SHOULD abort if
> extension is not present if they don't want to interop with
> legacy implementations.


Correct. But as you say, that's a check that you can omit. However, if you
only
implement the EMS derivation than (unless I'm missing something) even if you
omit the check this should just result in a handshake failure.

-Ekr




>
> -Ilari
>