MIFARE 4K​ (also known as MIFARE Classic 4K) is a widely used contactless memory card IC​ from NXP Semiconductors, based on the ISO/IEC 14443 Type A​ standard. It is one of the most recognized RFID chips for medium-security applications.

Key Technical Features

Security Model (Legacy Status)

The MIFARE 4K uses a sector-based security​ model:

• Each sector has two keys (Key A and Key B)​ for access control (Read/Write/Increment/Decrement).
• It relies on the MIFARE Crypto1​ algorithm, which has known vulnerabilities and is not recommended for high-security applications​ today.
• It is susceptible to cloning and replay attacks if physical access is possible.

Common Applications

Despite its security limitations, it remains popular due to its low cost and high compatibility:

• Access Control Systems​ (older building entry systems)
• Public Transportation​ (metro cards, bus passes)
• Loyalty & Membership Cards
• Library Management

Comparison with MIFARE DESFire

Unlike the MIFARE DESFire​ series (which has a secure microcontroller and file system), the MIFARE 4K is a simple memory card​ with limited processing logic.

Summary

The MIFARE 4K​ is a legacy workhorse​ of the RFID world. It is suitable for low-to-medium risk applications​ where cost and reader compatibility are critical, but should be avoided for payment or high-security access​ in favor of MIFARE DESFire​ or MIFARE Plus.