ISO/IEC 14443-4

ISO/IEC 14443-4 defines the transmission protocol layer for proximity contactless cards, establishing the half-duplex block exchange mechanism used by NFC Forum Type 4 tags. This protocol enables APDU (Application Protocol Data Unit) command exchange as defined in ISO 7816-4, supporting multi-application file systems, access control lists, and cryptographic operations. It is the foundation for MIFARE DESFire, NTAG 424, and all contactless payment card communication.