NFC ACR122U

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This page is for “NFC ACR122U” - USB NFC/RFID reader for card analysis and programming.

Commentary

The NFC ACR122U is a USB-based NFC/RFID reader that serves as an essential tool for exploring and working with various NFC card types. Based on my experience documented in Playing with NFC Cards , this device enables analysis of different card types including MiFare Classic, UltraLight, and NTAG variants.

Primary Use Cases: Card identification, sector analysis, key recovery, and card reprogramming for educational and authorized testing purposes. The device works well with various software tools for both reading existing cards and writing new data to formatted cards.

Technical Specs

Interface: USB 2.0
Supported Cards: ISO 14443 Type A/B, ISO 15693, Mifare Classic/Plus/Ultralight
Operating Frequency: 13.56 MHz
Communication: PC/SC compliant
Power: USB bus powered
Operating System: Windows, macOS, Linux
Dimensions: 85 x 54 x 5 mm

Supported Card Types

MiFare Classic 1K - 1KB memory, 16 sectors, 4 blocks each
MiFare UltraLight - Basic NFC functionality
MiFare NTAG216 - High capacity NFC tags
MiFare UltraLight EV1 - Enhanced UltraLight variant

Useful Applications

Card Analysis and Reading

NFC Tools - Android app for card identification and basic operations
MiFare Classic Tool - Comprehensive MiFare Classic card analysis
MCT-bruteforce-key - Fork with enhanced key recovery capabilities
PC/SC - Standard card reader interface
libnfc - Open source NFC library

Key Recovery and Security Testing

mfoc - Nested attack automation for MiFare Classic cards
mfcuk - Dark-side attack automation
MiFare Classic Tool - Sector analysis and key recovery
NFC ReTag - Alternative approach using unique card IDs

Card Programming

NFC Tools - Write data to formatted cards
Factory Formatting - Reset cards to original state
Custom Data Writing - Program cards with personal information
Contact Information - Create NFC business cards

Tips and Tricks

Card Analysis Workflow

Card Identification: Use NFC Tools to identify card types (MiFare Classic 1K, UltraLight, NTAG216, etc.)
Sector Analysis: Use MiFare Classic Tool to read all sectors with standard keys
Key Recovery: Use MCT-bruteforce-key for enhanced key recovery capabilities
Factory Formatting: Format cards to original state before reprogramming

Security Testing

Nested Attacks: Use mfoc for automated nested attacks on MiFare Classic cards
Dark-side Attacks: Use mfcuk for dark-side attack automation
Write Protection: Check for write locks before attempting to modify cards
Access Conditions: Understand sector access conditions and permissions

Card Reprogramming

Data Writing: Use NFC Tools to write custom data to formatted cards
Contact Cards: Create NFC business cards with contact information
URL Redirection: Program cards to redirect to specific URLs
Alternative Approach: Use NFC ReTag for unique ID-based card interactions

Best Practices

Educational Use: Use only for educational and authorized testing purposes
Card Handling: Handle cards properly to avoid damage
Driver Installation: Install proper drivers for your operating system
Cross-platform: Use libnfc for cross-platform compatibility

Reference material

Playing with NFC Cards