Buffalo Technology Secure Lock Ware - Manual (Page 8)

Enter your desired password twice and choose either AES 128
bit security or AES 256 bit security. Because this encryption is
extremely secure, information on your device will be inaccessible
if you forget your password. You may wish to enter a hint to help
you remember the password later. Click OK when done.
Configuration
If you click Yes on this screen, your device will be encrypted and
all data currently on it will be lost.
Click OK to finish configuration. Now, you’ll need to reformat
the device.