Signing Classes with the Netscape Object Signing Tool
Get a signing certificate from a CA, Certificate Authority, listed at https://certs.netscape.com.
Import the certificate to your Netscape Communicator browser.
Use The Netscape Object Signing Tool, which is a command line program, signtool, to sign JAR files. (Note that digital signature information is transmitted in JAR files);
Refer to the signed code as <APPLET CODE="signed.class" ARCHIVE="myjarfile.jar">
Use signtool to sign the classes and create a JAR file: signtool -d"path to certificate" -k"my CA" -e ".class” -Z myjar.jar