Passwords are not safe because if someone steals it they can access your online account. Imagine you could withdraw money at an ATM by just entering a PIN code. No ATM card required. Would you trust that? That would mean that if someone could get your PIN code, say by filming you at a grocery store checkout, they could clean out your checking account. But that is exactly what we have protecting most desktops and network access today—reliance only on passwords to identify you. Once someone has your user name and password, they can pretend to be you online, and this has become an unbearable threat to the digital world.