PGP

While you may or may not have heard of Pretty Good Protection (PGP), it is good to look into this if you are serious about security. PGP is a security protocol that you can use to encrypt texts through such things as email and PMs. All that is needed to start using PGP is a client (there are open source clients) and a PGP key, generated by your PGP client. Then when you want to send a message, you send you PGP key to a friend, and he sends you his, and you can communicate securely. There is more to it than that, but if you are interested, you can simply Google some tutorials on the matter. As for clients this one is pretty good.