 The full description of this latest and fastest attack to date can also be found in the IACR preprint archive.The new attack improves by a factor of more than 10 all previous card-only attacks on MIFARE Classic, has instant running time, and it does not require a costly precomputation.The new attack allows to recover the secret key of any sector of MIFARE Classic card via wireless interaction, within about 300 queries to the card.