I used an external WD hard drive for my backups, but it decided to not speak to the computer anymore last week. I assume it's the USB interface has died as it's no longer recognized by the computer.
So I pulled the drive out of it and plugged it in as in internal drive to the desktop computer. It could see the drive so it was still working, but it could not recognize the format of it.
Research showed me that western digital use a hardware encryption chip on the driver board to protect user data.
So if someone steals the hard drive out of my external drive they won't be able to read my data. If, on the other hand they steal the whole external hard drive, they will have the encryption chip too and can just plug it into their usb and read everything of mine.
This seems a spectacularly useless feature which just makes life hard for me - but maybe I can fix it now !