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Re: [TLS] draft-ietf-tls-exported-authenticator questions

Watson Ladd <watsonbladd@gmail.com> Sat, 22 July 2017 05:42 UTC

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From: Watson Ladd <watsonbladd@gmail.com>
Date: Fri, 21 Jul 2017 22:42:08 -0700
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To: Ilari Liusvaara <ilariliusvaara@welho.com>
Cc: Benjamin Kaduk <bkaduk@akamai.com>, "tls@ietf.org" <tls@ietf.org>
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Subject: Re: [TLS] draft-ietf-tls-exported-authenticator questions
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On Fri, Jul 21, 2017 at 10:34 PM, Ilari Liusvaara
<ilariliusvaara@welho.com> wrote:
> On Fri, Jul 21, 2017 at 10:17:08PM -0700, Watson Ladd wrote:
>> On Fri, Jul 21, 2017 at 12:55 PM, Benjamin Kaduk <bkaduk@akamai.com> wrote:
>> > Unrelated to Ilari's questions, I wonder if we want to say anything about
>> > certificate_request_context values being unique across both in-TLS
>> > post-handshake auth and exported authenticators.
>>
>> This context is not a security sensitive thing: it is for disambiguation.
>
> I'm not so sure about that.
>
> If crc is repeated within a connection, then the old certificate
> message can be replayed.
>
> If crc is guessed, then reply can be pregenerated anytime during
> connection.
>
> However, neither seems crticial, but might be of magnitude to note.

Yes, if we want  freshness then we need a challenge-response protocol.
I don't recall if the H2 draft does.

>
>
> -Ilari



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