Rednet Security

I've been working on a project that uses rednet to communicate through a client and server. I know that you can just open channels now so I wonder is there anyway I can secure this communication?

The best solution generally is to not worry about it. There isn't really any sensitive data passing through CC, so you can send everything in the clear on known channels.

Securing things "for the fun of it" is another matter. There are a variety of homegrown crypto solutions on these forums, some worse than others. Feel free to look around for one or create your own. It would be difficult to do worse than some of them.

The other way to go is using some crypto authentication to choose a session channel. You initiate a connection on a known channel, then the hosts exchange encrypted information used to verify the identity/authenticity of the client, before both hosts use common knowledge to select a new channel to communicate on in such a way that someone listening in doesn't have enough information to know what the channel will be.