How to add encryption key automatically in MS Enterprise Library

I'm a team member in developing an enterprise application that will be generating packages to submit to the enterprise contractors to install it at their PC.

One of my tasks is to add encryption to the application's fields. this was accomplished by add encryption key to app.config file and the key was generated by MS Enterprise Library manager.

In the above step I have to go to the manager application and create the key then copy it and paste it to the application config file. This is valid to be done in the current machine but once we created a setup project and generated a package and send it to the contractor, this step has to be done manually and at the contractor site.

Is there a way to generate the key and add it to the application config file automatically on the application setup or at package generation?

I hope that my case is clear and I need your help guys as I already tried to resolve this issue and the task due date is next week and I don't want to delay it.

Thanks in advance for everyone who is going to help.