Identification
SUN
Secure Unique NFC
The standard NXP scheme by which an authentication-grade NFC chip appends a per-tap signature to the URL it serves.
A SUN URL looks like an ordinary HTTPS link but carries extra query parameters — typically a UID, a monotonically increasing tap counter and a CMAC signature derived from a secret AES key burned into the chip.
The server holding the matching key can verify each tap is fresh and authentic. Anything missing, repeated or tampered is rejected — collapsing entire classes of clone and replay attack to a back-end check.
SUN is supported by NTAG 424 DNA and a handful of other authentication-grade chips.