On paranoia and privacy “The main problem is that everything in the real world is unique, so a skillful observation can reveal a signature that you can trace back to the owner. For example, consider a mobile device with cellular communication and the ability to use strong encryption with rotating media access control addresses to hide identity. Despite considerable effort to ensure that privacy is protected by the protocol, a radio frequency expert could carefully analyze the RF signature and find characteristics in the baseband signal that would be unique to the device (probably traced back to imperfections in the transistors or the crystal oscillator at the heart of the system). As the device’s owner will probably go home at some point, you could trace the signal to a house address and use a simple Web search to determine a name. You could then link the owner to sightings at other locations, determine the time they were there, and determine the transactions that occurred.”
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On paranoia and privacy

 
“The main problem is that everything in the real world is unique, so a skillful observation can reveal a signature that you can trace back to the owner. For example, consider a mobile device with cellular communication and the ability to use strong encryption with rotating media access control addresses to hide identity. Despite considerable effort to ensure that privacy is protected by the protocol, a radio frequency expert could carefully analyze the RF signature and find characteristics in the baseband signal that would be unique to the device (probably traced back to imperfections in the transistors or the crystal oscillator at the heart of the system). As the device’s owner will probably go home at some point, you could trace the signal to a house address and use a simple Web search to determine a name. You could then link the owner to sightings at other locations, determine the time they were there, and determine the transactions that occurred.”