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Smart card application protocol data unit

In the context of smart cards, 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 7816-4 Organization, security and commands for interchange.[1]

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 header (CLA, INS, P1, P2)[2] 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

  1. ^ ISO/IEC JTC 1/SC 17 (2005). "ISO/IEC 7816-4". International Organization for Standardization.{{cite web}}: CS1 maint: numeric names: authors list (link)
  2. ^ a b Celer, Victor (2021-12-25). "Using the SIMcard as a Security Module (HSM)". CelerSMS. 1 (2): 13–17. ISSN 2745-2336. OCLC 1295467772.

See also

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