So, the iPhone 5S has a fingerprint scanner built into the Home button. Pretty secure, am I right? Nooo! You can steal someone's fingerprint. For all Apple haters everywhere.
Or, you can go for putty. Over at Putty World they have yet another way to steal someone's fingerprint:
Tsutomu Matsumoto of Yokohama National University in Japan got the ball rolling in the cruelty-to-finger-scanners area with his study on the foolability of different scanners when presented with "fingers" made from silicone (the base substance in Thinking Putty) and gelatine (like Jell-O).
Matsumoto, in brief, fooled various sensors with fake fingers. Gelatine fingers worked better, because gelatine behaves, electrically, quite like real flesh; sensors that care about conductivity, which capacitive sensors do, aren't terribly likely to be faked out by a putty finger.
This scanner is optical and probably wouldn't know the difference, but I nonetheless decided to see if I could fool it with a gelatine finger.
The easiest way to make a fake fingertip is by taking a mold of a real finger, mixing up some gelatine solution, and then pouring it into the mold. Of course in real life this would require you to say, "Excuse me sir but I'd like to steal your fingerprint. Yes, just put your finger there and press!"
Image courtesy of Billdrastal.