Installing pgcrypto Extension
I'm assuming that you want to create this extension in another server. I'm guessing that the server didn't get the "postgresql contrib" package installed. This package contains the "standard" extensions that are available from the PostgreSQL source code.

I think you need to get the system administrator to install the required package for your OS.

For Debian and Ubuntu it's the "postgresql-contrib-9.1" package, for other platforms it has a similar name.