Per-volume zero-based one-time pad (PVZBOTP). It's a common technique used by almost all Fortune 500 organizations these days. The tl;dr is that you generate an

Per-volume zero-based one-time pad (PVZBOTP). It's a common technique used by almost all Fortune 500 organizations these days. The tl;dr is that you generate an encrypted volume that, when XOR'd with a volume consisting entirely of zeroes, produces the original plaintext volume.