 Also, the very first 16 bytes contain the serial number of the card and certain other manufacturer data and are read only.That brings the net storage capacity of these cards down to 752 bytes for MIFARE Classic with 1K memory, 3,440 bytes for MIFARE Classic with 4K memory, and 224 bytes for MIFARE Mini.It uses an NXP proprietary security protocol (Crypto-1) for authentication and ciphering.