I suggest take a look at the old wiki pages, this is explained there.
Furthermore you're exact question appears to be in the FAQ, which is somewhat hidden in the sources
You can try this link:
7. Can I run cajo over Secure Sockets Layer? Yes, of course. If you need to support pre JSE 5 clients, have a look here; you can copy the sample zip file, and replace the two socket factories in Remote. If all JVMs involved are certain to be using JSE 5 or higher; SSL/TLS socket factories are included in the runtime. Here is a very excellent example of this whole process. *However, a much more important question is; Would you want to? Please have a look at the following project discussion thread.
(Sorry cut not get links pasted, so use the above google cache link, normally there are hyperlinks in the text above).
I'm personally tring to implement a SSH tunnel for cajo, so I was looking for similar resources.