Re: [TLS] Privacy considerations - identity hiding from eavesdropping in (D)TLS

"Viktor S. Wold Eide" <viktor.s.wold.eide@gmail.com> Fri, 28 August 2015 14:28 UTC

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From: "Viktor S. Wold Eide" <viktor.s.wold.eide@gmail.com>
Date: Fri, 28 Aug 2015 16:27:28 +0200
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To: Eric Rescorla <ekr@rtfm.com>
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Cc: "tls@ietf.org" <TLS@ietf.org>
Subject: Re: [TLS] Privacy considerations - identity hiding from eavesdropping in (D)TLS
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On Thu, Aug 27, 2015 at 1:18 PM, Eric Rescorla <ekr@rtfm.com>; wrote:

>
>
> On Thu, Aug 27, 2015 at 2:14 AM, Viktor S. Wold Eide <
> viktor.s.wold.eide@gmail.com>; wrote:
>
>> On Mon, Aug 24, 2015 at 11:17 PM, Eric Rescorla <ekr@rtfm.com>; wrote:
>>
>>>
>>>
>>> TLS 1.3 encrypts both the client's and server's certificates already.
>>> The server's certificate is secure only against passive attack. The
>>> client's is encrypted with a key that the client can authenticate as
>>> belonging to the server.
>>>
>>>
>>
>> It's good to see that both the client's and the server's certificates are
>> encrypted in TLS 1.3, providing protection against passive eavesdropping.
>>
>> For some use cases it might be worthwhile to reduce the information made
>> available to an active attacker also. Are there any suggestions in this
>> direction for TLS 1.3?
>>
>> One might think of a multi stage approach, something like:
>> - Anonymous connection establishment, resulting in a secure channel.
>> - Authentication by means of group certificate.
>> - Authentication by means of a host specific certificate.
>>
>> The purpose of the second step above is to first only provide the group
>> identity to an active attacker, and then to reveal the host identities
>> (certificate information) only after group membership has been mutually
>> authenticated
>>
>
> I don't think this matches most TLS use cases very well, since the client
> generally isn't authenticated at all, so there's no point in the server
> progressively
> revealing more.
>
>
Although the client generally is not authenticated currently, TLS 1.3 and
DTLS 1.3 are likely to stay for a long time and then to be used for lots of
different use cases, including more peer-to-peer interaction. For some
use-cases, including peer-to-peer interaction, being able to progressively
reveal more information would improve protection. Whether this is a
worthwhile tradeoff or not, depends on many different factors. I think it
is both relevant and interesting to see to what extent (D)TLS 1.3 would
support such use cases.

Best regards
Viktor S. Wold Eide