A personal digital security device needs to be even stronger than an ATM card to protect PCs and network security.  ATMs are trusted devices, but PCs have many security flaws requiring a stronger key than what a standard magnetic stripe ATM card can offer.  Network security devices use smart card technology.  This is a small computer with its own software in a credit card-sized plastic card or USB token.  If it is a card, it has a gold contact on it.  You either insert this into a smart card-ready keyboard or laptop, or into a reader.  USB devices work like Flash drives, just plug it into a USB connector.