PGPSigner project is a tool born out of the main virtues of a sysadmin: Lazyness and Impatience. Have you ever been to a PGP key signing party? It is fun, you verify all these ids, check the keys on the party list and then... then you get home. And find out that you have 47 different keys to sign with one or more of your private keys. You will do it tomorrow. Surely.
When I found one of these lists from an event eight months past, I decided that I do not want to do all the work by myself. So PGPSigner was born: Strong cryptography and command line completion in a single application.
This application uses strong cryptography, something that might pose problems for you if you happen to live in a region of the world where this is an issue.
To use this application, you must probably install the "Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files" for the Sun JCE. If you encounter the following error.
java.lang.SecurityException: Unsupported keysize or algorithm parameters.
then this is most likely the problem. Download these for the Sun JDK 1.5 at http://java.sun.com/javase/downloads/index_jdk5.jsp (scroll down to the bottom of the page).