Bluetagging - friend or foe?

I'll highlight this interesting point from a recent Flickr uploader review article by Chris Heathcote.

The most controversial feature of them all is storing and publishing Bluetooth IDs. Are these personal information? Are you allowed to store this data (particularly in the EU)? It’s, well, illuminating from a privacy angle, but my take on it is that metadata is always useful. Already in Helsinki, with probably a few tens of users of both Meaning and Context Watcher, we’re seeing intersections between Bluetooth device IDs on photos: this means that a particular device/individual was nearby both ekurvine and myself when we took the pictures. The obvious benefits are that you could search for your own Bluetooth ID to get photos taken around you – such as at events, down the pub or at parties (could also be done similarly using a combination of cell ID and time).

To put it in another way: if you have your Bluetooth on, and someone snaps a picture with a camera phone near by, you might get "caught on the image", even if you don't appear in the picture at all. This is because every Bluetooth device has an unique identifier, and it announces it to about a 10-20 m radius, and this ID can be captured in the image, thus giving the viewer of the image information about who was present at the time.

A Bluetooth ID consists of 12 digits (like 01:02:03:04:05:06), so it's difficult to say who it is. But you can also ask for the Bluetooth friendly name (like "Janne's phone"), and one does need to be a datamining guru to figure out your BT address, if there is enough data available. To paint a nasty scenario: your jealous boyfriend checks out your BT address, and then goes online to find out where you have been moving lately to check up on you. This may become even more problematic, if any of the pictures is tagged with GPS data.

Now, here's the interesting question: does collecting the Bluetooth IDs which are present constitute collecting an person registry - and do you commit a violation of the Finnish law by posting an image with Bluetooth IDs onto a public website?

And regardless of whether it is illegal or not, should it be controlled, and how on Earth could you possibly control it, even if you wanted to? Perhaps the transparent society will happen completely accidentally and spontaneously, brought on us by teenagers who just want to have a bit of fun?

And, if private citizens are allowed to breach everyone's privacy and in the process collect huge databases on foreign soil, then would it not be hypocritical to say that governments and corporations can't do it too? What is the real difference between surveillance and sousveillance, in the end?

Anyway, if you're worried about your privacy, you might want to consider turning your Bluetooth to "non-discoverable mode", i.e. turn off the visibility to all devices... (Finnish Nokia S60 phones: Bluetooth->"Puhelimen näkyvyys" -> "Piilotettu").


"Does collecting the Bluetooth IDs which are present constitute collecting an person registry"

IANAL, I would argue that Bluetooth address by itself is not regarded as an inherent property of a person ("personal characteristics") - at least not yet, so Bluetooth MAC addresses themselves will probably not constitute a person registry, as they cannot by itself be connected to a person. The law says: "personal data means any information on a private individual and any information on his/her personal characteristics or personal circumstances, where these are identifiable as concerning him/her or the members of his/her family or household". However, if and when there is an image that shows the person whose phone's BT address is included in the picture, most probably this will be a personal data registry as then it will be "identifiable as concerning him/her".

Because "personal data file means a set of personal data, connected by a common use and processed fully or partially automatically or sorted into a card index, directory or other manually accessible form so that the data pertaining to a given person can be retrieved easily and at reasonable cost", just having information of nearby BT MACs does not constitute a personal data registry unless the database contains information that connects these BT MACs to physical persons.

"- and do you commit a violation of the Finnish law by posting an image with Bluetooth IDs onto a public website?"

Again, IANAL. A single image with the depicted person's Bluetooth ID is not a person registry as such but it definitely is personal data. Also, a photography (and publication of photos) taken in public space is lawful. However, the uploader is working as an agent of the Controller of the database, and hence would probably ensure that the basic requirements are satisfied for processing personal data. I do not think that the requirements would be satisfied in this case, if the image of the person contains the person's BT ID.

Moreover, "personal data may be transferred to outside the European Union or the European Economic Area only if the country in question guarantees an adequate level of data protection" so the company that runs the public website, if located outside EU/EEC, needs to subscribe to the Safe Harbour principles ( in order for the uploader not to break the law in this respect as well.

If the website is within EU/EEC, then it is supposed to have a directive-compliant privacy policy in place.

(English translations from FINLEX)

--avs, 22-Apr-2006

yikes. good post.

--PhilWilson, 23-Apr-2006

Thanks, avs and Phil.

Just in case you don't know, IANAL means "I Am Not A Lawyer", but I do trust avs's opinion on this, even if he isn't officially certified ;-)

--JanneJalkanen, 23-Apr-2006

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"Main_blogentry_210406_1" last changed on 21-Apr-2006 18:10:44 EEST by JanneJalkanen.

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