A Practical Attack on the MIFARE Classic

The MIFARE Classic is the most widely used contactless smart card in the market. Its design and implementation details are kept secret by its manufacturer. This paper studies the architecture of the card and the communication protocol between card and reader. It reveals command codes and structure that so far were unknown. It also gives a practical, low-cost attack that recovers secret information from the memory of the card. Due to a weakness in the pseudo-random generator we are able to recover the keystream generated by the CRYPTO1 stream cipher. Finally, we exploit the malleability of the stream cipher to read all memory blocks of the first sector of the card. Moreover, we are able to read any sector of the memory of the card, provided that we know one memory block within this sector.