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

Eric Rescorla <ekr@rtfm.com> Thu, 27 August 2015 11:18 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 27 Aug 2015 04:18:08 -0700
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To: "Viktor S. Wold Eide" <viktor.s.wold.eide@gmail.com>
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Subject: Re: [TLS] Privacy considerations - identity hiding from eavesdropping in (D)TLS
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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.

-Ekr

Does something like this seem reasonable for TLS 1.3 or are there any other
> ways for providing protection of identities against an active attack?
>


> Best regards
> Viktor S. Wold Eide
>
>