Fair warning; this solution is a bit of an overkill. If all you want to do is encrypt Tiddlywiki, it has it's own encryption utility that is every bit as secure which you can read about here: http://tiddlywiki.com/#Encryption.
Otherwise, if you also would like to backup other content along with TiddlyWiki, EncFS may be the solution for you:
This tut gives a brief overview on how to use EncFS to encrypt theTiddlyWiki data file before it is uploaded to the cloud.
Useful Links:
https://www.youtube.com/watch?v=yCEpL...
