In the context of

smart card A smart card, chip card, or integrated circuit card (ICC or IC card) is a physical electronic authentication device, used to control access to a resource. It is typically a plastic credit card-sized card with an embedded integrated circuit (IC) c ...

s, an application protocol data unit (APDU) is the communication unit between a smart card reader and a smart card. The structure of the APDU is defined by

ISO/IEC 7816 ISO/IEC 7816 is an international standard related to electronic identification cards with contacts, especially smart cards, and more recently, contactless mobile devices, managed jointly by the International Organization for Standardization (ISO) ...

-4 ''Organization, security and commands for interchange''.

APDU message command-response pair

There are two categories of APDUs: command APDUs and response APDUs. A command APDU is sent by the reader to the card – it contains a mandatory 4-

byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...

header (CLA, INS, P1, P2) and from 0 to 65 535 bytes of data. A response APDU is sent by the card to the reader – it contains from 0 to 65 536 bytes of data, and 2 mandatory status bytes (SW1, SW2).

References

{{reflist

External links

Smartcard ISOs, contents

Selected list of smartcard APDU commands

Selected list of SW1 SW2 Status bytes

Smart cards ISO standards IEC standards