said by Guspaz:
Presumably they're decrypting the content when they save it to disk, or at least, not using the same on-disk encryption as they use for the actual broadcast...
They would I assume they don't, and the reason they don't is so that you can't take that hard drive out and use it somewhere else like on a computer. The decryption happens upon viewing. There is no need to decrypt when saving to the hard drive only to reencrypt again.
Even if they do, encryption processors are so advanced that it should be a non-issue as far as being able to handle multiple streams in excess of three.