Also you may add additional passwords to your already encrypted drive. Here’s some details:
It says that you can have up to 8 passwords/keys (I’ve used two).
The command you need is
sudo cryptsetup luksAddKey /dev/sdaX
sdaX should be your LUKS partition. More details are in the article.
Please be careful, you can loose access to you encrypted data if you seriously mess the passwords. Though just adding new LUKS password doesn’t invalidate old one, they are used simultaneously (and you need only one of them to decrypt the drive), there are commands to delete password and possible change exiting ones.
The idea is this: first you ensure you use English US layout, then you add new password to your LUKS drive/partition, then test if new one works upon reboot.