You can put the key on the disk itself too--you just need to zero out the space containing the key when you're done. That's how phones with encryption and remot

You can put the key on the disk itself too--you just need to zero out the space containing the key when you're done. That's how phones with encryption and remote wipe features usually do it. In fact, a lot of SSDs, e.g. Samsung's, already work this way, transparently AES-encrypting data before it is written. (With AES in hardware, the overhead is negligible, even for high-performance drives.) The "Encryption" feature they advertise actually just lets you set your own key for the encryption key container--it happens either way.