sudo cryptsetup --verify-passphrase luksFormat <imgFile|device> -c aes -s 256 -h sha256

# Open to /dev/mapper/securebackup
sudo cryptsetup luksOpen <imgFile|device> securebackup

# Format
sudo mkfs -t ext3 -m 1 -O dir_index,filetype,sparse_super /dev/mapper/securebackup