06 · 14 min
NFC at 13.56 MHz
ISO 14443, NDEF records, and why MIFARE Classic's age is a history lesson — not a license to copy badges.
NFC is 13.56 MHz RFID with a pile of standards on top: ISO 14443 A/B for most phones and bank cards, ISO 15693 for longer-range 'vicinity' tags, FeliCa in some transit. NFC Forum Types 1–5 describe how those chips store NDEF — the URL / text / vCard format your phone already understands.
Work at the right layer
| Layer | Question it answers | Own-gear example |
|---|---|---|
| UID | Which chip did I hear? | Logging a blank NTAG's serial |
| NDEF | What user data is in the user area? | A URL you wrote to a tag on your keyring |
| Sector keys / crypto | Am I allowed to read this memory? | Out of scope unless the tag is a blank you own |
| Secure element / DESFire / bank | Can I pretend to be a payment or transit app? | Never — not in this bench, not as a 'test' |
NDEF is the friendly lab
Buy a pack of NTAG213 or NTAG215 blanks. They are cheap, meant to be written, and they speak NFC Forum Type 2. Write a URL to your own site or a note to yourself. Confirm a phone taps it. Lock the tag only if you understand that lock bits are often permanent. That loop — read, write, verify — is the skill.
MIFARE Classic, as history
MIFARE Classic 1K/4K still shows up on older access systems. Its cipher, Crypto-1, was broken in the academic literature around 2008. The chip is organized into sectors with Key A / Key B. A public UID is not that key. Knowing the history is useful so you can explain to a building owner why Classic is the wrong tool in 2026. Recovering keys from a live access system you do not own is not a lab; it is an attack on an access device.
What stock Flipper is for here
- Read UID and try to parse NDEF on a tag you own.
- Write NDEF to a blank NTAG.
- See that a bank card is detected and then leave it alone.
- Understand that 'the UID showed up' is not authentication.
DESFire, Plus, and secure-element designs exist because Classic failed. When a vendor still ships Classic on a door, the fix is to replace the door system — not to practice on it in the wild.
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