Scientists at the University of Newcastle have discovered a way to turn the inherent randomness caused by the manufacturing of paper into a security feature, per The Economist.
The technique: Light is shined through the paper and a picture is taken with a normal digital camera. That image then has a special filter applied to it, which produces two long numbers that serve as the paper's unique "fingerprint." The whole process only takes just over a second.
A use: Instead of bulky and easily-damaged RFID chips, this technique could be used to ensure passport security around the world.