Safe as in "will it fry my brain?"...or do you mean safe as in "can anybody detect my SSN, DNA, etc?"
I work for an RFID company. The technology they're describing is called "Passive RFID" which means there's a circuit embedded within your passport
card, but that circuit has no battery or other power source of it's own. It's essentially the same exact system used for toll roads. So what happens
is that as you get within 30' of the RFID hardware you enter a field of energy produced by a passive RFID "interrogator". I believe the maximum
energy allowed for the interrogator is 4 watts so it won't fry your brain very quickly...but it's risky to your health to stand near the interrogator
for long periods of time like the border crossing workers do.
The energy field powers the circuits in your passport card and your card starts wildly transmitting a unique number that identifies you in the INS
database. The transmission does not include anything but this number...no SSN etc.. So, what does this mean for privacy? Well, the hardware to
activate your card and to read the transmission it sends is cheap and relatively easy to configure. You can get it on eBay for <$100. On the
other hand, the ID number your card transmits is useless unless you have information to tie it to...so you either have to have a copy of the INS
database if your goal is to pull personal information. On the other hand, if you're a bad seed and you want to track an individual person for
whatever reason, then you can get close to them once, read the ID number their card sends out and record it. Then you can track an individual by
placing readers and antennas at various places and you can know whenever that individual goes near that place.
Of course, this whole system can be thwarted by wrapping your passport card in a single layer of tin foil.
