دراسة معمقة في ISO 14443
{# Answer-first lead — frontend-gold-standard §1.1. Expects `lead` (plain text, already resolved by apps.content.leads). Rendered directly under the h1 so the self-contained answer is the first prose a reader, a SERP snippet, or an AI extractor meets. No curated-data gate: the view always supplies either curated content_summary or a computed fallback. #}Contactless smart card communication protocol. It covers ISO 14443 Deep Dive, Type A vs Type B Physical Layer, Anticollision and Card Activation, APDU over Contactless, and NFC and ISO 14443. The guide is part of the Standards & Protocols series and about 4 minutes of reading.
ISO 14443 Deep Dive
ISO 14443 is the international standard for contactless smart card communication at 13.56 MHz. It defines the physical layer, the initialisation and anticollision sequences, and the transmission protocol used by transit cards, passports, banking cards, and access badges worldwide.
Use the ATR Parser to decode the ATS (Answer To Select) returned by ISO 14443-4 cards, and the Card Type Identifier to distinguish card families from UID and ATS data.
Type A vs Type B Physical Layer
ISO 14443 Part 2 defines two physical layer variants operating at 13.56 MHz carrier with a base bit rate of 106 kbps. Parts 3 and 4 layer initialisation and protocol on top.
| Property | Type A | Type B |
|---|---|---|
| Modulation (reader→card) | 100% ASK (amplitude shift) | 10% ASK |
| Encoding (reader→card) | Modified Miller | NRZ-L |
| Modulation (card→reader) | OOK load modulation | BPSK load modulation |
| Encoding (card→reader) | Manchester | NRZ-L |
| Anticollision scheme | Bit-oriented slot loop | Time-slot with AFI |
| Unique identifier | UID (4, 7, or 10 bytes) | PUPI (4 bytes, may be random) |
| Card examples | MIFARE, NTAG, DESFire | Calypso, SIM (contactless mode), some passports |
Both types support higher bit rates of 212, 424, and 848 kbps through the PCD (proximity coupling device, i.e., reader) sending a rate selection command after successful activation.
Anticollision and Card Activation
When multiple cards are within reader range, the reader must resolve which card to communicate with. The process differs by type:
Type A uses a bit-oriented loop: the reader sends a SELECT command with a known UID prefix; cards whose UID matches respond with the next bit. Collisions are resolved bit by bit, isolating one card per loop cycle.
Type B uses a probabilistic time-slot scheme: the reader broadcasts a REQB with a number-of-slots field (1, 2, 4, 8, or 16). Each card picks a random slot and responds with its ATQB if not already in HALT state. A successful ATTRIB command then dedicates the channel to one card.
After selection, both types optionally enter the ISO 14443-4 protocol layer (T=CL — contactless transport). Cards that support only Part 3 (MIFARE Classic, NTAG) terminate at anticollision and use proprietary commands. Cards that respond to RATS (Request for Answer To Select) with an ATS response support the full ISO 14443-4 command transport.
APDU over Contactless
ISO 14443-4 wraps APDU messages in I-blocks (information blocks) with sequence numbers, R-blocks (receive-ready/not-ready), and S-blocks (supervisory: WTX, DESELECT, PARAMETERS). This block structure provides the same error-recovery semantics as ISO 7816 T=1 over the contactless channel.
The APDU payload itself is identical to contact-mode APDUs as defined in ISO 7816-4. The SELECT AID command uses the same AID format, and responses carry the same SW1 SW2 status words. This design means a dual-interface card can expose the same applet logic to both contact and contactless readers.
NFC and ISO 14443
The NFC Forum's NFC-A (ISO 14443-3 Type A) and NFC-B (ISO 14443-3 Type B) modes map directly onto the underlying standard. A smartphone acting as an NFC reader follows the same anticollision and activation procedure as a dedicated smart card terminal, making smartphone-based card emulation (HCE — Host Card Emulation) or embedded secure element transactions possible with the same card-side APDU logic.
Key Metrics for Reader Design
| Parameter | Specification |
|---|---|
| Carrier frequency | 13.56 MHz ± 7 kHz |
| Operating field | 1.5–7.5 A/m (H-field) |
| Maximum card power | ~10 mW (harvested) |
| Minimum read distance (near-field) | 0 cm (touch) |
| Maximum read distance (spec) | 10 cm |
Antenna design is critical: coil geometry, tuning capacitance, and quality factor Q determine both maximum range and susceptibility to detuning by nearby metal surfaces.
Continue to EMV Payment Architecture for how EMV builds a payment transaction layer on top of ISO 14443 and ISO 7816.
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Frequently Asked Questions
What is the difference between ISO 14443 Type A and Type B?
Type A modulates reader-to-card traffic with 100 percent ASK using modified Miller encoding and returns OOK load modulation with Manchester encoding; Type B uses 10 percent ASK with NRZ-L in both directions and BPSK load modulation on the return path. Type A identifies cards by a 4, 7, or 10-byte UID and resolves collisions with a bit-oriented slot loop; Type B uses a 4-byte PUPI, which may be random, with time-slot anticollision and an AFI.
Which cards use Type A and which use Type B?
MIFARE, NTAG, and DESFire products are Type A. Calypso, contactless SIM operation, and several passport implementations use Type B. Both variants operate on the same 13.56 MHz carrier.
Can ISO 14443 run faster than 106 kbps?
Yes. The base bit rate is 106 kbps, and both types support 212, 424, and 848 kbps once the proximity coupling device — the reader — sends a rate selection command after successful card activation.
Who are the smart card guides written for?
Our guides cover a range of experience levels. Getting Started guides introduce smart card fundamentals. Security guides address Common Criteria certification and key management. Programming guides target developers working with APDU commands, JavaCard applets, and GlobalPlatform card management.
Frequently Asked Questions
What is the difference between ISO 14443 Type A and Type B?
Type A modulates reader-to-card traffic with 100 percent ASK using modified Miller encoding and returns OOK load modulation with Manchester encoding; Type B uses 10 percent ASK with NRZ-L in both directions and BPSK load modulation on the return path. Type A identifies cards by a 4, 7, or 10-byte UID and resolves collisions with a bit-oriented slot loop; Type B uses a 4-byte PUPI, which may be random, with time-slot anticollision and an AFI.
Which cards use Type A and which use Type B?
MIFARE, NTAG, and DESFire products are Type A. Calypso, contactless SIM operation, and several passport implementations use Type B. Both variants operate on the same 13.56 MHz carrier.
Can ISO 14443 run faster than 106 kbps?
Yes. The base bit rate is 106 kbps, and both types support 212, 424, and 848 kbps once the proximity coupling device — the reader — sends a rate selection command after successful card activation.
Who are the smart card guides written for?
Our guides cover a range of experience levels. Getting Started guides introduce smart card fundamentals. Security guides address Common Criteria certification and key management. Programming guides target developers working with APDU commands, JavaCard applets, and GlobalPlatform card management.