loclass_notes.md

About LOCLASS attack

This document is primarily intended for understanding hf iclass loclass and files used with it.

LOCLASS aim is to recover the used masterkey for that specific reader configured in Elite mode / High Security mode.

LOCLASS, is a two part attack. First is the online part where you gather needed information from the reader by presenting a carefully selected CSN and save the responses to file. For the first part you run hf iclass sim -t 2 and take notice of the saved filename.

The second part is offline, where the information gathered from the first step is used in a series of DES operations to figure out the used masterkey. run hf iclass loclass -f abc.bin

If you don't have access to a iClass SE reader configured in Elite mode there is a test file which you can use. hf iclass loclass -f iclass_dump.bin

Unit testing

In order to verify that loclass is actually working, there is a "unit" test mode. run hf iclass loclass --test.

This test mode uses two files.

• iclass_dump.bin this is a sample file from hf iclass sim -t 2, with complete keytable recovery, using 128 carefully selected CSN and the file contains the MAC results from reader.
• iclass_key.bin this is file shall contain the legacy masterkey, AA1 key. loclass uses it to verify that permutation / reversing / generation of key is correct.