How exactly do I create a signed JAR for use with the Java Plug-in?

http://developer.java.sun.com/developer/qow/archive/99/ explains how to create a test certificate and sign your JAR file.

If you are using Java Plugin 1.3, JAR files signed using Netscape Object Signing is also supported. More information on Deploying RSA Signed Applets In Java Plug-in can be found at http://java.sun.com/products/plugin/1.3/docs/nsobjsigning.html