This would be for something like a personal journal or close-friends only blog posts while keep the rest of the site open.
You could agree on a source text with your friends in an out-of-band way, then everyone just has to go and download whatever book/song/etc that you agree on in order to decode your articles.
Anybody who isn't 'in-the-know' will just see gibberish.
That said, I'm using the Stanford JavaScript Crypto Library on https://github.com/gabrielsroka/gabrielsroka.github.io/blob/...
What about authentication? Maybe putting it on a Google doc and sharing it with certain people?