If IIS does not have "machine key" , then install "ASP.NET" under "Server Roles --> Web Server IIS --> Application development" in install features.
1. select "machine key " from IIS Home . Right Click "machine key" and select "Open feature"
2. In machine key generate window, slect the validation metho and Encryption method as per requirement and click "generate Keys"
You will get the keys, as shown above.