For contactless payments on point-of-sale machines, which technology is commonly used?

The technology most commonly used for contactless payments on point-of-sale (POS) machines is Near Field Communication (NFC). NFC enables devices to communicate wirelessly when they are in proximity to each other, typically within a few centimeters. This capability is essential for contactless payment systems, allowing users to tap their smartphones, smart cards, or other NFC-enabled devices against a terminal to complete a transaction quickly and securely.

NFC facilitates the transmission of payment information between the customer’s device and the POS terminal without the need for physical contact, which not only speeds up the payment process but also enhances convenience and hygiene—especially relevant in today's context.

In contrast, while Bluetooth is a wireless technology that allows devices to connect over greater distances, it is not typically utilized for contactless payments directly due to its broader range and different communication protocols. Simultaneous Authentication of Equals (SAE) is primarily a security protocol and not associated directly with contactless payments. Galois Counter Mode Protocol (GCMP) is a cryptographic protocol used primarily for secure communications rather than payment processing itself.

Overall, NFC's design specifically for short-range communication makes it the ideal choice for secure and efficient contactless payment systems.