FiSH is a plugin/module that facilitates encrypted chatting over IRC. It's available for mIRC, xChat and Irssi.
Adding FiSH to mIRC
Adding FiSH to xChat
Adding FiSH to Irssi
This requires light editing of a Makefile and compiling from source, nothing too difficult if you RTFM.
Proceedure Outline Download, unpack and build the MIRACL library for handling large numbers. Download and unpack the FiSH source. Copy the MIRACL.so library (built in step 1) to the FiSH source directory. Edit the makefile to point to paths for glib and irssi Compile FiSH Move the compiled plugin to irssi's folder.
Needed Packages: MIRACL FiSH opt: Irssi (If you did not compile Irssi from source, you will need to get the irssi headers from the irssi source for compiling FiSH)