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Re: [TLS] ESNI: Tracking and blocking via record_digest

Rob Sayre <sayrer@gmail.com> Mon, 25 November 2019 20:38 UTC

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From: Rob Sayre <sayrer@gmail.com>
Date: Mon, 25 Nov 2019 12:37:56 -0800
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To: Ben Schwartz <bemasc@google.com>
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Subject: Re: [TLS] ESNI: Tracking and blocking via record_digest
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You're right, this is all there in the draft. It's just scattered around a
bit, and "anonymity set" is used only once and not defined.

I filed an issue https://github.com/tlswg/draft-ietf-tls-esni/issues/204 in
case the editors want to consolidate text on this concern.

thanks,
Rob


On Mon, Nov 25, 2019 at 11:25 AM Ben Schwartz <bemasc@google.com> wrote:

> The record_digest, like the ESNIConfig itself, is intended to be constant
> across all domains that form an anonymity set (i.e. O(1) ESNIConfigs per
> CDN).  Thus, the record_digest reveals no additional information to an
> onlooker who can observe the server IP.
>
> On Mon, Nov 25, 2019 at 2:03 PM Rob Sayre <sayrer@gmail.com> wrote:
>
>> Hi,
>>
>> I see the issue of tracking and blocking via record_digest has come up a
>> few times in the github repository, but I don't understand the resolution.
>>
>> If someone wanted to observe or block traffic to "example.com", couldn't
>> they retrieve the ESNI keys, calculate the record_digest themselves, and
>> then use that to spot traffic to "example.com"?
>>
>> Is the idea that DNS providers will vary the shared keys?
>>
>> thanks,
>> Rob
>>
>> _______________________________________________
>> TLS mailing list
>> TLS@ietf.org
>> https://www.ietf.org/mailman/listinfo/tls
>>
>

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