Researchers have proven it’s possible to train a special-purpose deep-learning algorithm that can guess 4-digit card PINs 41% of the time, even if the victim is covering the pad with their hands.

… By using three tries, which is typically the maximum allowed number of attempts before the card is withheld, the researchers reconstructed the correct sequence for 5-digit PINs 30% of the time, and reached 41% for 4-digit PINs.  Read More