RFID and NFC Security

Contactless tags control physical access, payments, transit, inventory, and identity. RFID (Radio Frequency Identification) and NFC (Near Field Communication) power building badges, hotel keys, transit cards, and tap-to-pay.

Because these systems gate physical security, weaknesses translate directly into doors that open and payments that move. Many deployments still rely on technology with known, decade-old breaks that organizations never replaced.

• Cloning a badge can grant full building access.
• A weak hotel lock system can be opened with a cheap reader.

Understanding the frequency and chip type is the foundation of any assessment.

Contactless tags split into two main frequency families with very different security:

• Low Frequency (125 kHz) — older proximity cards like HID Prox and EM4100. Short range, no cryptography; they simply broadcast a fixed ID.
• High Frequency (13.56 MHz) — NFC, MIFARE, transit, and payment cards. Supports memory, sectors, and in better chips, cryptography.

The 125 kHz cards are trivially cloned because they have no authentication at all. The 13.56 MHz family ranges from broken (MIFARE Classic) to robust (DESFire EV2/EV3).