[thatsso1999]

I believe your math is off by a factor of 1000.

125kHz = 125,000 cycles/sec * 2 bits/cycle = 250,000 bits/sec

250,000 bits/sec / 40 bits/code = 6250 codes/sec

2^40 = 1,099,511,627,776 possible codes / 6250 codes/sec ~= 175,921,860 sec ~= 5.578 years

While this is still an extremely long time for the worst case, by the looks of other comments, as well as the author's video, it appears extremely doubtful that most RFID readers have anywhere near 40 bits of security - and it takes about 10 seconds (65536/6250) for the fuzzer to brute force all codes 16 bits or less.

[TheSoftwareGuy]

Shoot you're right, it's kHz not Hz haha I'll update my comment.

[TheSoftwareGuy]

Darn I don't think HN is letting me update my comment.