can't update ubuntu 12.10(problem-GPG error: http://archive.canonical.com quantal Release:)

Hai frnds i am using ubuntu 12.10 some failures will be
i am refered this link: https://answers.launchpad.net/ubuntu/+source/apt/+question/211305 but same problem coming pls solve
my problem is after update given:

root@ramachandra-HP-dx2080-MT-GN203AV:/home/ramachandra/Downloads# sudo apt-get update
Get:1 http://ppa.launchpad.net quantal InRelease [2845 B]
Get:2 http://archive.canonical.com quantal InRelease [2835 B]
Get:3 http://ppa.launchpad.net quantal InRelease [2851 B]
Get:4 http://archive.canonical.com quantal Release.gpg [2831 B]
Get:5 http://ppa.launchpad.net quantal InRelease [2856 B]
Get:6 http://archive.canonical.com quantal Release [2827 B]
Get:7 http://archive.ubuntu.com quantal InRelease [2831 B]
Get:8 http://archive.ubuntu.com quantal-updates InRelease [2839 B]
Get:9 http://ppa.launchpad.net quantal Release.gpg [2841 B]
Get:10 http://ppa.launchpad.net quantal Release.gpg [2847 B]
Get:11 http://archive.ubuntu.com quantal-security InRelease [2840 B]
Get:12 http://ppa.launchpad.net quantal Release.gpg [2852 B]
Get:13 http://archive.ubuntu.com quantal Release.gpg [2833 B]
Get:14 http://ppa.launchpad.net quantal Release [2837 B]
Ign http://archive.canonical.com quantal Release
E: GPG error: http://archive.canonical.com quantal Release: The following signatures were invalid: NODATA 1 NODATA 2

i am follwed this below procedure:-
sudo grep -R proxy /etc/apt/*
sudo fuser -vvv /var/lib/dpkg/lock
cat /etc/lsb-release
uname -a
sudo rm /var/lib/apt/lists/lock
sudo cp -arf /var/lib/dpkg /var/lib/dpkg.backup
sudo mv /var/lib/dpkg/status /var/lib/dpkg/status-bad
sudo cp /var/lib/dpkg/status-old /var/lib/dpkg/status
sudo mv /var/lib/dpkg/available /var/lib/dpkg/available-bad
sudo cp /var/lib/dpkg/available-old /var/lib/dpkg/available
sudo rm -rf /var/lib/dpkg/updates/*
sudo rm -rf /var/lib/apt/lists
sudo rm /var/cache/apt/*.bin
sudo mkdir /var/lib/apt/lists
sudo mkdir /var/lib/apt/lists/partial
LANG=C;sudo apt-get clean
LANG=C;sudo apt-get autoclean
LANG=C;sudo apt-get --purge autoremove
LANG=C;sudo apt-get --purge autoremove
LANG=C;sudo apt-get update -o APT::Cache-Limit=25165824Ign
sudo dpkg --configure -a
sudo dpkg --clear-avail
LANG=C;sudo apt-get -f install
LANG=C;sudo apt-get --fix-missing install
LANG=C;sudo apt-get update -o APT::Cache-Limit=25165824 && sudo apt-get dist-upgrade
find /etc/apt -name '*.list' -exec bash -c 'echo -e "\n$1\n"; cat -n "$1"' _ '{}' \;
sudo apt-key adv --recv-key --keyserver keyserver.ubuntu.com A040830F7FAC5991
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 437D05B5 3E5C1192
sudo apt-get update
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install launchpad-getkeys