ISO/IEC 7816-4 Abbreviations and Notation for Smart Card Commands

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Smart Card Abbreviations and Notation

ISO 7816 Part 4: Interindustry Commands for Interchange

ISO 7816 part 4, section..1 2 3 4 5 6 7 8 9 annex.. A B C D E F

Abbreviations and notation used in smart-card work

Smart-card documentation is dense with three-letter abbreviations and a hexadecimal notation that is easy to misread. This page is Ambimat’s working reference for both.

Notation conventions

  • Hexadecimal values. Byte values are written in hexadecimal. Different documents mark this differently — '9000', 0x9000, and 9000h all appear in the field. Whichever convention you adopt, apply it consistently in your own specifications, because an unmarked 10 meaning sixteen has caused more than one defect.
  • Bit numbering. Within a byte, bits are conventionally numbered b8 (most significant) down to b1 (least significant). This is the opposite of the zero-based, LSB-first numbering common in general software work, and it is the single most frequent source of misread bit-field descriptions.
  • Concatenation. The symbol || denotes joining byte strings end to end.
  • Don’t-care bits. An x in a bit pattern means the value is not significant for that description.

Command and response fields

  • APDU — Application Protocol Data Unit; the command or response message at application level.
  • TPDU — Transmission Protocol Data Unit; what actually travels over T=0 or T=1 once framing is applied.
  • CLA — class byte. Carries the command class, logical channel number, and whether secure messaging is applied.
  • INS — instruction byte. Identifies the command.
  • P1, P2 — parameter bytes. Their meaning is defined per command; together they often carry an address, a reference, or an option selector.
  • Lc — length of the command data field, when data is sent to the card.
  • Le — expected length of the response data field. A value of zero conventionally means “the maximum available”.
  • SW1, SW2 — the two status bytes ending every response. Together they are the status word.

File system and data

  • MF — Master File, the root.
  • DF — Dedicated File, a directory.
  • EF — Elementary File, a data file.
  • FID — File Identifier, a two-byte reference.
  • SFI — Short EF Identifier, a compact five-bit reference letting a command name a file without a separate SELECT.
  • FCI, FCP, FMD — File Control Information and its two constituent templates, File Control Parameters and File Management Data, returned on selection.
  • AID — Application Identifier, up to 16 bytes, comprising a registered application provider identifier and a proprietary extension.
  • DIR — the directory file listing applications present on a card.
  • TLV / BER-TLV — Tag-Length-Value encoding, in the Basic Encoding Rules form used throughout Part 4.

Interface and protocol

  • ATR — Answer to Reset, the card’s opening byte string.
  • PPS — Protocol and Parameter Selection, the optional negotiation after the ATR.
  • IFD — Interface Device; the reader or terminal.
  • ICC — Integrated Circuit Card; the card itself.
  • T=0, T=1 — the byte-oriented and block-oriented transmission protocols.
  • IFS — Information Field Size, the negotiated maximum block payload under T=1.
  • NAD, PCB, LEN, EDC — the node address, protocol control byte, length and error detection code fields of a T=1 block.

Security

  • SM — Secure Messaging.
  • MAC — Message Authentication Code; in this context often called a cryptographic checksum.
  • CRT — Control Reference Template, describing which key and algorithm an operation should use.
  • PIN — Personal Identification Number, a form of reference data.

Authoritative source

For the normative list of abbreviations and the notation used in the standard itself, refer to ISO/IEC 7816-4:2020, published by ISO. The reference above is Ambimat’s own compilation for working use.