On Jul 24, 2017, at 8:59 PM, Christopher Morrow <morrowc.li...@gmail.com> wrote:
> and at the cache->auth layer it's potentially the case that the provider can 
> say: "use precision of /24" or "use precision of /17" ? So, there's really 
> not much "pii" that can be worried over at the provider-cache-resolver (they 
> already know who you are...) and they (provider) can decide how much 
> granularity is "important" to release to the upstream authoritative cache.

There is no such thing as an upstream authoritative cache.   The filtering is 
being done at the cache.   This is not client subnet: this is client ID.   So 
the cache, which is not authoritative, is receiving PII about a specific client 
machine.   Being able to filter the PII at the CPE would indeed improve privacy 
in this case; the problem is that the CPE has to have a UI or API that allows 
that to happen, and they don't.

The reason DNS filtering is useful is not that it is forced upon the end user, 
but that it allows devices that use the default cache to get filtering in a way 
that does not depend on the software installed on them.   So e.g. your IoT 
device can be infected by a worm but not actually exfiltrate any private 
information to the attacker, because the attacker's DNS is blocked.

Being able to know that a particular device is a particular device is actually 
quite useful in this context; unfortunately, there is no way to distinguish 
"useful" and "personally-identifying".   Even if you only identify the IoT 
devices in your home, by doing so you reduce the search space for identifying 
the other devices.

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