GPG error:public key is not available

I have a NAS, and when i try to run apt-get update, I got a series of warning messages  like below

W: GPG error: http://ftp.us.debian.org squeeze Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY AED4B06F473041FA NO_PUBKEY 64481591B98321F9

W: GPG error: http://ftp.us.debian.org wheezy Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010 NO_PUBKEY 6FB2A1C265FFB764

This link gave me the solution. You copy your keys, and run the following command


sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys AED4B06F473041FA

You can either run it for each key, or separate each key by space

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys  AED4B06F473041FA 64481591B98321F9