Pavol Rusnak #cypherpunk #hacker #openhw #privacy #bitcoin #newmediaart

NFC Tags in Prague Metro

Prague Metro is full of advertisements, which are posters put in frames like this:

nfc-metro

Have you noticed something interesting in the picture?

How about now?

nfc-metro-detail

Don’t worry, I haven’t notice it either at first, until my friend Sargon pointed that out.

So this white circle looks like a NFC tag (and yes, it is there even when there is a poster over it).

Let’s try it out!

I am using Nexus 5 phone with NFC TagInfo by NXP application installed.

This is how it looks when you approach the tag with this app running:

nfc-metro-a-reader1

nfc-metro-a-reader2

nfc-metro-a-reader3

nfc-metro-a-reader4

The most important thing on the last screen are dots that appear between the sector number and its contents. This means that the area is unlocked and writable (x means locked, . unlocked). Yay!

Why is the tag not locked and anyone can write to it? I can only speculate, but I think that’s because the advertisement company uses the tags to track which frame has which ad and they care only about the tag ID, which cannot be overwrittern.

Let’s try another application called NFC TagWriter by NXP.

nfc-metro-b-writer1

Select Write tags button.

nfc-metro-b-writer2

Select New dataset

nfc-metro-b-writer3

I will be creating a link so I choose Link.

nfc-metro-b-writer4

After filling in the details I click Save.

nfc-metro-b-writer5

Now I can select data from my list.

nfc-metro-b-writer6

Let’s write it by clicking on Write!

nfc-metro-b-writer7

Now we can touch the tag.

nfc-metro-b-writer8

Success!

Now when we approach the tag with the phone, Android will read the tag, interpret the URL and open browser with this address.

The information on the tag can be used to trigger lots of other events too. Call a number, send an email, launch an application, show plain text or send or receive bitcoins (when bitcoin:address URI scheme or Bitcoin private key is used).

When we use the TagInfo application now, it will look like this:

nfc-metro-c-reader1

nfc-metro-c-reader2

nfc-metro-c-reader3

nfc-metro-c-reader4

nfc-metro-c-reader5

When I was experimented with the tags, I haven’t found any which had any data stored in it.

I hope next time I try this, there will be some nice poems (106 chars maximum) or links to some nice pictures. Heck, someone could even create an interesting augmented reality game, capture the flag, check-in (who wants to be a mayor of this train?) or …

The only limit is your imagination. And slow (or none) internet in the metro. :-(