[ubuntu] Software center not connecting

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http://ubuntuforums.org – I am using Ubuntu 11.04. I can't install chinese chess software from the Ubuntu Software Center or from terminal. I am getting errors such as: Requires installation of untrusted packages: The action would require the installation of packages from not authenticated sources. Any install that I'm trying through the Software Center is telling me the error text in bold. Additional information: Here's a paste from apt-get update: Reading package lists... Done W: GPG error: http://ppa.launchpad.net oneiric Release: The following signatures couldn't be verified because the public key is not availa (Hardware)