How do I erase an encrypted TimeMachine drive on Mountain Lion if I've forgotten the password?
Solution 1:
Just found the answer here. Basically, from the terminal, type:
sudo diskutil cs list
You'll get a list of your drives and a bunch of related info. Look for the one you want to format and grab its Logical Volume Group's UUID. It should look something like this:
Logical Volume Group XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
Then erase the drive by executing the command:
sudo diskutil cs delete XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
Now you should be able to see the drive and format it using Disk Utility.