Re: [perpass] privacy implications of UUIDs for IoT devices

George Michaelson <> Thu, 06 October 2016 00:30 UTC

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From: George Michaelson <>
Date: Thu, 6 Oct 2016 10:29:57 +1000
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To: Dave Thaler <>
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Cc: "" <>, Peter Saint-Andre - Filament <>
Subject: Re: [perpass] privacy implications of UUIDs for IoT devices
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btw, my primary goal was illustrative not specific. persistent ID
threats are not exactly like MAC threats, but they probably lie in a
similar space. I have no major concern with the desire to be
deterministically both unique and known, I have this concern that the
mechanisms a manufacturer can use there, tend to processes (IEEE
Registry) which construct higher state (vendor-specific blocks) which
have side effects.

On Thu, Oct 6, 2016 at 10:09 AM, Dave Thaler <> wrote:
> The issue with IEEE MAC's is that it's sent to untrusted observers, not that it is a stable identifier per se.
> It just so happens that you typically don't have a choice but to send it in packets such that it can be observed
> by untrusted observers, hence the need to use randomized MACs.
> -----Original Message-----
> From: George Michaelson []
> Sent: Wednesday, October 5, 2016 5:01 PM
> To: Peter Saint-Andre - Filament <>
> Cc:; Dave Thaler <>
> Subject: Re: [perpass] privacy implications of UUIDs for IoT devices
> As an example the IEEE MAC registry is really only to provide uniqueness, but its been demonstrated to act as a passive-capture mechanism to identify probable host architecture from on-the-wire sniffs. This then leads directly to: "If its a Dell, then I know the iDrac default password so I can attempt to see if this is a badly configured Dell which has iDrac IPMI on the host address" and like attacks.
> Unique identifiers are being used by the cellular provider to offer price differentiated service to people on the same basic substrate.
> Which is a poshed-up way of saying you can get a SIM which is dataplan for an iPad but if you put it in your phone you are in breach of contract over the use of that SIM. I am not personally a fan of this legalism, but it is legal, and it is an ism.
> I think there is a fundamental tension between baked in uniqueness, probabalistic uniqueness (think ULA) and non-unique state in Layer-2 and Layer-3
> -G
> On Thu, Oct 6, 2016 at 9:54 AM, Peter Saint-Andre - Filament <> wrote:
>> Over on the CORE WG list, we've had a little discussion about the
>> desirability (or not) of unique identifiers for devices in the
>> Internet of Things. The message below provides some context.
>> I'd be curious to learn more about the attack surface lurking behind
>> Stephen Farrell's comment that having long-term stable identifiers for
>> IoT devices is a privacy-unfriendly practice because people will abuse such identifiers.
>> To be clear, the scenarios I have in mind are not specific to CoAP and
>> don't always involve IP-based networking (the technology I'm working
>> on these days enables mesh networking over long-range radio), but they
>> do involve discovery and eventual communication that is both
>> end-to-end encrypted and as close to metadata-hiding as possible.
>> Thanks!
>> Peter
>> -------- Forwarded Message --------
>> Subject: Re: [core] Implications of IP address / port changes for CoAP
>> & Co
>> Date: Thu, 6 Oct 2016 00:11:26 +0100
>> From: Stephen Farrell
>> To: <>
>> Hi Peter,
>> On 06/10/16 00:03, Peter Saint-Andre - Filament wrote:
>>> On 10/5/16 4:28 PM, Stephen Farrell wrote:
>>>> On 05/10/16 23:22, Dave Thaler wrote:
>>>>> It is important that every device have a unique UUID that is
>>>>> endpoint-address-agnostic and protocol-agnostic.
>>>> Considering the privacy implications I'm not at all sure I'd accept
>>>> that argument. In fact I'd argue we ought encourage that devices not
>>>> have globally unique long-term identifiers at all unless there is a
>>>> real need for those, and unless we understand how to control their
>>>> (ab)use.
>>> By "identifier" do we necessarily mean "network identifier"? It seems
>>> to me that it is useful to have a unique long-term identifier for
>>> every device, based on its public key. Whether you can obtain a
>>> network connection to that device based on such information is another story.
>> It is undoubtedly useful to have long term stable identifiers of
>> various kinds. I'd include key IDs and public keys as such.
>> Turns out that it's also fairly universally privacy unfriendly as
>> people will abuse such identifiers for good and bad reasons.
>> So I think we need to get much better at analysing when such things
>> are really needed and in what scope. My bet is that a lot of the time
>> a locally or probabilistically unique more transient identifier would
>> be just fine.
>> But yeah, I can't prove that. OTOH there is a hint in the term "IMSI
>> catcher" isn't there?
>> Cheers,
>> S.
>>> Peter
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