http://www.pcworld.com/article/2845072/ubuntu-owncloud-and-a...
Part of the value of a service like LastPass (not a fan personally, but for argument sake I think ths still holds for this issue) is that someone is (should be) always on duty to monitor the service for suspicious activity and be ready to respond to security issues in the code base. While you're in class or a meeting or a movie or asleep, they can already be locking ish down and implementing patches / fixes.
These are always a bit of a balancing act on what's good use of third-party services and what's worth handling yourself. Services hopefully have a competent team behind it monitoring it (not guaranteed though!), but at the same time provide a much more lucrative attack target. And in my case at least, in a completely different jurisdiction. Monthly feels, service continuity, learning aspect... There are lots of different points influencing the choices.
Instead of Dropbox you can also use https://spideroak.com/ They have a really handy program which let you control a lot of things and they are a "zero knowledge" cloud provider, all your data is encrypted. Snowden recommends them: http://www.theguardian.com/technology/2014/jul/17/edward-sno... For $12 dollar a month you get 1 TB, which you can use as a safe off-site backup location.
Which itself _is_ open source: https://github.com/SpiderOak/Encryptr
When are exporting and offline access coming?
Also, for the database file encryption I'm using AES256 with 10 million encryption rounds (configurable in the application), which hopefully slows down any brute force attempts even in case of a data breach.
Of course, all bets are off if your device itself is compromised, but that would be the case with any solution.
Applying AES multiple times/rounds doesn't yield anything. AES is not adaptive (like BCrypt) so the cost of brute-forcing doesn't increase incrementally with the number of rounds.
Anyway, the slowdown is noticeable on my devices with these applications (it's about one second on my laptop), but then again these obviously are not custom-built AES decrypters. This will have to do now.