Cryptocat is an open source project that allows users to create private encrypted chat rooms. Cryptocat can be installed in Firefox, Chrome, Safari, or as Mac desktop application. After installing Cryptocat open the application, enter a room name and username, then click connect. To have others join you in your chat room they have to know and enter the encryption key provided by Cryptocat.
For those of you who get that nostalgic feeling when you see old 8 bit graphics, Cryptocat will make you feel like a kid again.
Applications for Education
I often talk about using TodaysMeet for backchanneling in the classroom (I featured TodaysMeet in this free PDF about classroom backchannels). The only complaint that hear repeatedly about TodaysMeet is that you cannot password protect your conversations. Cryptocat allows you to do that. Cryptocat is not going to be for everyone, the encryption keys are long and it has a very "old school" geeky feel to it. But if you're up for it, Cryptocat might be the backchannel tool for you.