Seems that I have missed one of the most interesting speeches at 24C3.
Henryk Plötz and Karsten Nohl presented the recent developments in reverse engineering the Mifare RFID card. What they basically did is polishing away the different layers of the chip in the Mifare card and then visually analyze the layers, trying to find the cryptographic relevant parts. The security of the low-end Mifare Classic cards is to be concerned as broken. “Start migrating!” 😉 This does not have an impact on the high-end Mifare DESFire card. Check out the video!
Torrent of the video recording in Matroska / Vorbis / H.264
Torrent of the video recording in MPEG-4 / AAC-LC / H.264