Forewarning, i feel this is long winded and that some info may not be important, most of it is just background. TLDR at the bottom
So I’m currently working on helping a coworker clone his home fob so he can give one to gf. I’ve been trying a bunch of different methods and so far no luck and unfortunately I can only test 3 things a day since I have to wait till the next day to see if anything worked (i only have 3 magic gen1 tags) and i cant keep his fob because its the only he can open his door. But it has been a great way to learn how to use both my Proxmark3 and flipperzero.
I noticed today that I had gotten a 1024 error while doing an “hf mf cload” to one of the fobs but kind of just waved it off. After getting home, I grabbed a magic gen4 card and a 4th gen1 tag I’ve been learning with and tried recreate the error, no luck, so I did an “hf mf cview” to see what it all looked like and noticed that a couple lines were ever so slightly different from what my flipper had told me when I first started this. This is what I found:
Of the 2 files from my flipper and the only file i have from my proxmark3, these two lines are different between all of them. My current working theory is that his door rewrites this sector as a form of clone protection (im going to test this theory tomorrow by reading his fob again, i only just learned what “hf mf autopwn” does and only the proxmark3 file has any data beyond sector 2). This sector and sector 2 are also the only two sectors that don’t require a key to read. All other sectors had to be autopwn-ed to see and the flipper just came back with “?” for everything.
Does anyone know if this a method of clone protection or possibly the tag being misread multiple times? Or experienced this at all and know whats going on
TLDR: helping a coworker clone fob, noticed that I have multiple files where 2 of the lines are different. Can a fob reader rewrite data as a form of clone protection?