As far as I know, the tool bruteforce every possible hexadecimal keys to find the good one and then be able to read the data inside a mifare card.
Quote:Here are some default transport keys for empty (factory issued) Mifare Classic tags.Keyspace should be 16^12.
ffffffffffff
a0b0c0d0e0f0
a1b1c1d1e1f1
a0a1a2a3a4a5
b0b1b2b3b4b5
4d3a99c351dd
1a982c7e459a
000000000000
d3f7d3f7d3f7
aabbccddeeff