Then BitCasa _can_ tell what files you have. Here's a hypothetical scenario. Suppose Random Joe's machine is searched by the MAFIAA , and they find some videos

Then BitCasa _can_ tell what files you have. Here's a hypothetical scenario. Suppose Random Joe's machine is searched by the MAFIAA , and they find some videos downloaded via torrents. Then the MAFIAA guys just have to compute the same hash that BitCasa does on these files (or blocks), and submit a subpoena to BitCasa for the users who have files with the same checksums. For a cloud service to be truly appealing to me, it must offer full client-side encryption. In other words: no one (short of, maybe, the NSA and its zillion quantum computers) should be able to tell what files I have; not even their names.