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Possible Duplicate:
Updates don't install because of “untrusted packages”
Duplicate sources.list entry but cannot find the duplicates?

I am getting below GPG error on running the command sudo apt-get update.

W: GPG error: http://in.archive.ubuntu.com precise Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>
W: Duplicate sources.list entry http://archive.canonical.com/ubuntu/ precise/partner i386 Packages (/var/lib/apt/lists/archive.canonical.com_ubuntu_dists_precise_partner_binary-i386_Packages)

Also, I am not able to install applications from software center. Every time I install it shows a dialog box with the message,

Requires Installation of Untrusted packages
The action would require the installation of packages from not authenticated sources.

OK or Repair options does nothing.

share|improve this question

marked as duplicate by jokerdino, Eliah Kagan, Mitch, fossfreedom Sep 1 '12 at 7:35

This question was marked as an exact duplicate of an existing question.

    
Try this one too - askubuntu.com/a/64544/25798 – jokerdino Sep 1 '12 at 2:08
    
And this one as well - askubuntu.com/questions/156227/… – jokerdino Sep 1 '12 at 2:08
    
got it, thank you – Dinesh Sep 1 '12 at 2:59

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