The EMV (Chip & PIN) protocol requires ATMs and point-of-sale terminals to generate a random number. If this number (known in EMV terminology as the "unpredictable number") isn't random, Chip & PIN is left vulnerable to the "pre-play" attack, which is indistinguishable
from card cloning to the bank which issued the card. In the course of investigating a fraudulent transaction, for which the bank had refused to reimburse the victim, we discovered that ATM random number generators, across some of the biggest brands, have serious
By modifying a Chip & PIN card, and by reverse engineering ATM firmware, we analysed random number generators, finding a variety of different types of failures. The results of the survey can be found in our
blog post and
academic paper, announced at
CHES 2012 today.
See also coverage in the