[Bug 818448] [NEW] Not able to update or upgrade using sudo apt-get

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i am not able to upgrade or update in terminal. it is showing following
error:

W: GPG error: http://archive.canonical.com natty Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster at ubuntu.com>
W: GPG error: http://ppa.launchpad.net natty Release: The following signatures were invalid: BADSIG 9ED9A781DD9300F1 Launchpad PPA for Артём Попов
W: Failed to fetch bzip2:/var/lib/apt/lists/partial/archive.canonical.com_dists_natty_partner_binary-i386_Packages  Hash Sum mismatch

W: Failed to fetch http://ppa.launchpad.net/lorenzo-
carbonell/atareao/ubuntu/dists/natty/main/source/Sources  404  Not Found

W: Failed to fetch http://ppa.launchpad.net/lorenzo-
carbonell/atareao/ubuntu/dists/natty/main/binary-i386/Packages  404  Not
Found

E: Some index files failed to download. They have been ignored, or old
ones used instead.

** Affects: apt (Ubuntu)
     Importance: Undecided
         Status: New

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Not able to update or upgrade using sudo apt-get
https://bugs.launchpad.net/bugs/818448
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