I had a very good/lucky experience with recovering a xEM chip that I thought I had bricked today so I wanted to share my experience in case it helped anyone else.
So I’ve had a xEM implanted for well over a year now using it happily multiple times a day, every-day. However today I attempted to add my chip to the alarm system at work (not for the first time either), after trying I learnt from the alarm engineer who was on-site that he had discovered that this particular alarm system did not just passively read the ID from the card but it actively wrote data to the chip.
As with my previous attempts the coupling failed, so I thought nothing more of it and carried on with my day. When I returned home later that evening my chip wouldn’t work with any of my various systems around the house. Panick started to set in.
Luckily I had a backup of my xEM’s unique code stored in a safe place, so I could access the systems I needed to, but still I wasn’t happy thinking I had potentially bricked my xEM with a tear-off whilst writing or something like that.
Research online quickly lead me to post after post all referring to Proxmark3 devices, which I have known about and wanted for quite some time but finances can’t warrant such an expensive device for me at present.
Anyway, in my desperation I remembered about this old reader/writer I had bought ages ago either off eBay or Bang-good.
I remembered that the device only read one of my two implants but I couldn’t recall which. Thankfully it read my 125khz xEM.
This device also has the capability to write (even though I had never tried it with my xEM). Out of desperation I stuck in the UID that I had stored safe that was originally on my xEM and I pressed write. To my surprise it wrote instantly and said it was succesful.
I immediately used the same device to read it to double-check the UID - the code was different, completely different, the code was wrong but consistent on subsequent reads. However, when I presented my hand to all of my normal 125khz readers attached to other systems they now successfully detected the xEM’s original code! Which I am very happy about, because I have built and programmed various systems to work around that code.
My xEM is now back in action, working as it did before.
I have seen those devices sell for £27 on eBay or $46 on Bang-good, substantially cheaper than a Promark3 (as much as I would love one of those!)
Obviously I can’t vouch or garantee that this will work in everyones situation as we could all be in slightly different situations, so experiment at your own risk. But hopefully this helps someone somewhere one day. I’m in the south-west UK if anyone needs to borrow my unit they are welcome to.
It might have been the case that my xEM wasn’t even bricked, but just the code blanked or reset by the alarm system in work and I panicked, but either way I’m guessing others could be in a similar situation and I just want to help.
I would like to cross-post this on other similar “bricked xEM” threads but I don’t know how that would quite work or if it would be allowed?