FIX: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32 [SOLVED]

[SOLVED] NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32

During updating my ubuntu packages from command line using

apt-get update

or

apt update

I got the following errors

W: GPG error: http://security.ubuntu.com trusty-security InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32

W: GPG error: http://archive.ubuntu.com trusty-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32

W: GPG error: http://archive.ubuntu.com trusty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32

W: GPG error: http://archive.canonical.com trusty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32

SOLVE THIS ISSUE BY TYPING THE FOLLOWING COMMANDS:

apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 40976EAF437D05B5

apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 3B4FE6ACC0B21F32