I assume that my data stored online is ...

ROT13 isn't secure. That's why I only use a one-time pad for encrypting all my files. In order to reveal as little information about my files as possible, I choose the pad carefully so that it only stores zeroes on the server, and then I keep the pad safe locally.

This also has the advantage that it works without network access; if I need my encrypted files while I'm on the move, I can simply decrypt /dev/null with the appropriate key in order to retrieve my data. Additionally, I require very little space, as I compress all my cloud data down to a single disk block, plus some metadata. I also encrypt this compressed data, just to be safe, by the same method.