RFID/NFC FAQ

Practical answers for common RFID/NFC lab questions, from “why won’t this read?” to “why doesn’t cloning work?”

What is the difference between 125 kHz and 13.56 MHz?

They are different ecosystems with different protocols and security properties. Treating all cards as “NFC” causes many troubleshooting mistakes.

Why does card reading fail intermittently?

• Coil alignment and distance issues
• Metal or shielding near the card/reader
• Wrong band mode selected in your tool
• Weak field coupling due to antenna geometry

Can every card be cloned?

No. Modern secure cards may expose identifiers but keep protected data behind cryptographic authentication. In defensive systems, backend checks make naive cloning attempts fail even if a UID is copied.

What is a common defender mistake?

Relying only on a static identifier without challenge-response, revocation, and policy controls.

How should I troubleshoot a badge system in a lab?

1. Identify band and protocol family first.
2. Verify stable read geometry and remove interference variables.
3. Document what is public vs protected on-card.
4. Test backend enforcement (revocation, anti-passback, policy).
5. Record evidence and remediation recommendations.