techblog 

This evening I was trying to find out about the security of jabber conversations. After a unconvincing web search, I was just about to start playing with tcpdump to figure it out for myself when I discovered that PSI supports GPG in order to provide end-to-end security for your conversations. I am sure lots of you knew this already but it was news to me!

When you set up an account in PSI you can specify a GPG key to use and PSI will ask you for the passphrase when it starts. Your key ring will also need to contain the public keys of anyone you wish to send encrypted messages to.

When you create or modify an account in PSI you may find that the OpenPGP section is grayed out. There is some discussion of this problem here however I found that my problem was that GUI applications did not have the correct PATH set. In order to set the environment variables for GUI applications you need to create a plist file called ~/.MacOSX/environment.plist that looks something like this:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist
SYSTEM "file://localhost/System/Library/DTDs/PropertyList.dtd">
<plist version="0.9">
<dict>
<key>PATH</key>
<string>/sw/bin:/sw/sbin:/bin:/sbin:/usr/bin:/usr/sbin:
/usr/X11R6/bin</string>
</dict>
</plist>

(I got this info from http://developer.apple.com/qa/qa2001/qa1067.html)

To use GPG encryption in PSI you just click on the green lock symbol in the chat window and if necessary associate that jabber user with their GPG key.

UPDATE: I have since realised that a better way to do this would have been to use the OSX port of GnuPG from here. This version of GPG installs in the correct path so that PSI can find it and provides a nice GUI to gpg.