Since they'd want to deduplicate equal files across different users, to save bandwidth and storage costs, I imagine the keys they use won't be user-by-user. Th

Since they'd want to deduplicate equal files across different users, to save bandwidth and storage costs, I imagine the keys they use won't be user-by-user. They'd be defined file-by-file, or block-by-block, with the keys being stored elsewhere (but where?), or there's just one universal master key. Considering their security is just theatrical in nature, I'd bet they have one master key.