I'm fascinated by these smart card readers implemented into the public transport systems in my country (its the same technology in all countries that use it). I often buy these 5 day bus passes which are made of cardboard
you just hold hold them up to the scanner
for a second and it makes a bleeping sound to give the bus driver the go ahead to let you on the bus. From what I've gathered, this is just internationally standardised smart card technology. In my city you can also buy these plastic cards which work for the train and tram too, these ones don't expire, you just top them up when you need more credit and I think you need ID to buy them. If you dissolve these plastic cards in acetone, you'll be left with just the circuitry.
Some people do this so they can attach the circuitry to their watch as an alternative to carrying a card around with them. http://boingboing.net/2008/05/05/paying-for-the-londo.html
This is the same technology as Dublin smart cards, in London they're called Oyster cards.
Since this forums about hacking, I'll dedicate this thread to the intellectual challenge of figuring out how to hack this system. How can one hack this system? As we all know, to be able to hack a system we must first understand it. Heres what I've gathered so far. The circuitry in the card contains a coil that powers the circuit when EM radiation induces currrent in it (in this case its radio waves from the scanner). I also heard that it contains a capacitor, what it would need that for I have no idea. The circuitry contains non volatile RAM for storing its info. The circuitry will only interact with the external EM field if it receives the correct encryption key. This encryption key is modulated into the radio waves emitted by every one of these smart card scanners. I'm not too sure if everything I said there is accurate, I only started researching this but if this is how it works then it would be in the hackers interest to be able to replicate this encryption key. The device to record this encryption key emitted by the scanner would be a handheld spectrum analyser but I don't know how much a device up to this task would cost. I know nothing about cryptography and I'm a layman when it comes to electronics but I'm fairly sure the combined knowledge of people on this forum is more than enough to figure out how to hack this smart card technology system.