# Identify card type using nfc-list (libnfc) nfc-list
A MIFARE Classic 1K card contains 16 sectors, each with 4 blocks of 16 bytes (64 blocks total). The 4K variant contains 40 sectors—sectors 0-31 have 4 blocks each, while sectors 32-39 have 16 blocks each.
If you have a standard commercial USB RFID reader, you can turn your PC into a recovery station using open-source libraries. : ACR122U or PN532-based USB readers. mifare classic card recovery tool
: Before editing any hex values or keys, save a clean .mct or .bin dump of the card.
The fourth block of every sector is the "Sector Trailer." This block stores two secret cryptographic keys (Key A and Key B) alongside access conditions for that specific sector. The Crypto1 Weakness # Identify card type using nfc-list (libnfc) nfc-list
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Recovery tools use three primary types of attacks to crack these keys: : ACR122U or PN532-based USB readers
> FF 00 00 00 01 D4 40 01 60 01 FF < D5 41 00 ... (encrypted response)
Run a quick diagnostic to ensure the reader recognizes the card and can view its Unique Identifier (UID): nfc-list Use code with caution. Step 3: Executing a Dictionary Attack