NFC (Near Field Communication)

NFC, or near field communication, is the short-range radio technology behind contactless payment at a till. Hold a card or a phone close to a reader and the two talk for a moment. That short chat is what carries the payment data. The NFC Forum, which sets the specifications, describes NFC as contactless communication over a radio using a base frequency of 13.56 MHz, with a typical range of up to 2cm and data rates from 46kbit/s up to 1.7Mbit/s.

The very short range is a feature, not a flaw. A radio that reached a metre would let a reader talk to a card in a pocket, or to two cards at once. Keeping the working gap to a couple of centimetres means the user has to hold the card or phone close on purpose. It also makes listening in from a distance far harder. The Forum gives a certified range of 5mm, which is closer still than most people assume.

The Modes NFC Can Work In

The Forum lists several. Card emulation, where a phone acts like a card. Reader and writer mode, where a device reads a tag. Peer-to-peer, where two devices swap data. There is even wireless charging, which transfers up to 1W of power. Payments use card emulation. Knowing that helps explain why a phone can act like a card without holding one. The reader does not need to know the difference.

Where The Card Details Sit

There are two ways to do card emulation, and the split matters. With a secure element, the card is emulated by a dedicated chip inside the device. With host card emulation, an app in the device host does that work instead. The first keeps the sensitive stuff in hardware. The second is more flexible, and it shifts more of the trust onto software and the network behind it. Both are in wide use, so neither is the odd one out.

The Standards Underneath

NFC is not one standard but a stack that lines up with several. The Forum states compatibility with ISO/IEC 14443 Type A and Type B, ISO/IEC 15693, ISO/IEC 18092 and JIS-X 6319-4. Its specifications index adds that the Digital Protocol sits on top of 14443 and 18092 and covers bit rates of 106, 212 and 424 kbps. There are 5 tag types, each lined up with a different one of those base standards. Payments use only a slice of all this, but the slice rests on the whole stack. There is a shared data format too, called NDEF. That is how tags and devices agree on what they are sending each other.

How Payments Use It

The payments layer sits above the radio. EMVCo's contactless chip technology page describes consumers waving or tapping a device at a terminal, with a one-time security code generated for every payment to guard against fraud. It names two parts worth knowing. A contactless kernel is the software that lets the till handle these payments. A proximity coupling device is the hardware in the reader that runs the radio link at the point of sale. EMVCo published a fresh kernel spec in October 2022, a reminder that this layer keeps moving.

Why A One-Time Code Matters

This is the part that separates a tap from a magnetic stripe. A stripe carried the same static data every time, so a copy of it was as good as the card. A contactless payment generates a fresh code for each tap, which is designed to make a captured copy less use later. It is a strong design, though calling it unbreakable would go further than the proof does. The code is short-lived, not magic.

Tap Limits And Where They Come From

The cap on a contactless payment before a fuller check is needed is not set by NFC at all. It comes from local rules and scheme practice, and it differs by country and by card. That is why the same phone taps freely in one market and asks for a code in another. The tech is the same. The rules round it are not, so limits are worth checking market by market. A cap that has not moved in years is a common cause of taps that ask for a PIN when nobody expects it.

Cards, Phones And What Changes

A contactless card and a phone tap use the same radio, but not the same credential. A phone generally presents a network token rather than the card number, and it usually asks the user to unlock the device first. finera.'s look at Apple Pay against Google Pay covers how the two main wallets differ in practice, which matters more for a build than the shared radio does.

What This Means In A Shop

For a retailer the practical questions are mundane and worth asking anyway. Whether the readers handle the current kernel versions. Whether the tap limits in each market are set right. And whether staff know what to do when a tap fails and the customer needs another route. finera.'s piece on digital wallets in retail covers the counter-level detail, and its payment gateway sits behind the tap, where the payment is actually authorised.

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