I presume that the de-duplication saves them enough bandwidth and storage to allow a much lower price point (as well as the free plans) A secure system can't d

I presume that the de-duplication saves them enough bandwidth and storage to allow a much lower price point (as well as the free plans) A secure system can't do either of those things, as far as I know. Assuming the data is encrypted per-user, on their local devices, you can't easily compress it (because the files are now very high entropy), and you can't scan for preexisting files, because you'd be giving an attacker an oracle about which files (or rather, which file hashes) exist already. Even then, you could probably use some traffic analysis to deduce something about the data. Having data securely stored also removes some of the dropbox unique(ish?) features, like being able to share content with people via the web. The pretty much diametrical opposite of dropbox is tarsnap. Everything else sits somewhere in the middle.