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Proxmark 3

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Attacking RFID Systems with Proxmark3

The first thing you need to do is to have a Proxmark3 and install the software and it's dependencies.

Attacking MIFARE Classic 1KB

It has 16 sectors, each of them has 4 blocks and each block contains 16B. The UID is in sector 0 block 0 (and can't be altered). To access each sector you need 2 keys (A and B) which are stored in block 3 of each sector (sector trailer). The sector trailer also stores the access bits that give the read and write permissions on each block using the 2 keys. 2 keys are useful to give permissions to read if you know the first one and write if you know the second one (for example).

Several attacks can be performed

proxmark3> hf mf #List attacks

proxmark3> hf mf chk *1 ? t ./client/default_keys.dic #Keys bruteforce
proxmark3> hf mf fchk 1 t # Improved keys BF

proxmark3> hf mf rdbl 0 A FFFFFFFFFFFF # Read block 0 with the key
proxmark3> hf mf rdsc 0 A FFFFFFFFFFFF # Read sector 0 with the key

proxmark3> hf mf dump 1 # Dump the information of the card (using creds inside dumpkeys.bin)
proxmark3> hf mf restore # Copy data to a new card
proxmark3> hf mf eload hf-mf-B46F6F79-data # Simulate card using dump
proxmark3> hf mf sim *1 u 8c61b5b4 # Simulate card using memory

proxmark3> hf mf eset 01 000102030405060708090a0b0c0d0e0f # Write those bytes to block 1
proxmark3> hf mf eget 01 # Read block 1
proxmark3> hf mf wrbl 01 B FFFFFFFFFFFF 000102030405060708090a0b0c0d0e0f # Write to the card

The Proxmark3 allows to perform other actions like eavesdropping a Tag to Reader communication to try to find sensitive data. In this card you could just sniff the communication with and calculate the used key because the cryptographic operations used are weak and knowing the plain and cipher text you can calculate it (mfkey64 tool).

Raw Commands

IoT systems sometimes use nonbranded or noncommercial tags. In this case, you can use Proxmark3 to send custom raw commands to the tags.

proxmark3> hf search UID : 80 55 4b 6c ATQA : 00 04
SAK : 08 [2]
TYPE : NXP MIFARE CLASSIC 1k | Plus 2k SL1
  proprietary non iso14443-4 card found, RATS not supported
  No chinese magic backdoor command detected
  Prng detection: WEAK
  Valid ISO14443A Tag Found - Quiting Search

With this information you could try to search information about the card and about the way to communicate with it. Proxmark3 allows to send raw commands like: hf 14a raw -p -b 7 26

Scripts

The Proxmark3 software comes with a preloaded list of automation scripts that you can use to perform simple tasks. To retrieve the full list, use the script list command. Next, use the script run command, followed by the script’s name:

proxmark3> script run mfkeys

You can create a script to fuzz tag readers, so copying the data of a valid card just write a Lua script that randomize one or more random bytes and check if the reader crashes with any iteration.

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