RFID Tech: Credit cards tap into radio tags

From BBC - Technology, Apr 1, 2004 ... A leading professor at the Massachusetts Institute of Technology has suggested using radio tags in credit cards as a kind of virtual signature. Professor Ted Selker said the way someone moved their finger over the card would alter the radio transmission producing a signal unique to that person. I could have some gesture and that would be my signature he said it would be like a personal handshake.