Reprogramming the DT-xEM for use with HID readers

Recently started a new job, large building and every door locked with HID RFID readers and everyone has a RFID keycard around their neck to open the doors.
I already had the Dangerous Things xEM ATA5577 microchip in my left arm (EM400 emulation) but I bought an unwritten ATA5577 chip from cyberize.me.
I did the initial tests on the cyberize chip, still in the packaging and when I got that working I decided to try to write it to my DT chip.
While the standard readers managed to read both chips very well the keypad readers had a very hard time reading the cyberize.me chip, even though it wasn’t even inside me.
I tried using a handheld RFID copier I bought online but it didn’t work
(Thankfully these are quite cheap)
I knew I could do this with the Proxmark3 but at 450$ I thought it was too expensive, so I decided to try out some cheap RFID writer from aliexpress
(I believe multiple versions of this exist, not all supporting HID cards)
In the aliexpress listing was a download link for the software for it, hosted on a Chinese server, it was pretty hard to navigate so I decided to keep a copy on my server as all
The software is very minimalist but it does its job. It can read and write ID’s
While getting the RFID reader/writer to read my keykard was very easy it did have a hard time reading the small RFID implant, I attempted to remove the antenna from the reader but it was hot glued to the plastic case (real quality construction) but after some trial and error I managed to find a small “sweetspot” on the reader where I was able to read and write the chip
(by pressing my arm against this location and spamming the write button I finally manged to write to the chip)
- Note: The writer software adds 1 to the ID each time write is pressed, to write a specific ID to it you must keep correcting the ID
I had a friend assist me with the final writing to the chip, him correcting the ID and spamming the write button while I moved the writer around on my skin.
And voilla, the DT xEM chip now works with the HID keycard system at work