how to make password protected jar file?

[Kapil Keskar]

Hi guys,
I have done one executive jar file which will execute on dble click.
But i wanted to put it on security aspect .
It should ask me pwd while extracting for safety.
I know it is done in jdk1.4.
It is done through keytool & jarsigner.
but is it possible to do it without the certificate of vendor.
Or can you tell me any other way of protecting the code for tampering?
needed hard.......
Kapil