How to install software that "Requires installation of untrusted packages"?

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http://askubuntu.com – I am using Ubuntu 12.10. When I try to update the software, it shows me this error: Requires installation of untrusted packages This requires installing packages from unauthenticated sources. Details kalzium-data kanagram kate-data kde-l10n-engb kde-l10n-zhcn kde-runtime-data kdegames-data klettres-data libakonadi-kabc4 liblxc0 libwildmidi-config libwildmidi1 lxc marble-data nepomuk-core-data parley-data tomboy (HowTos)