GPG error : http://repos.rcn-ee.net

when I update using apt-get update on Beaglebone black, I got the following error,

W: GPG error: http://repos.rcn-ee.net trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D284E608A4C46402

I've tried following command given in some forum

$ apt-key adv --keyserver keyserver.ubuntu.com --recv-key D284E608A4C46402
Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --homedir /tmp/tmp.YlaPkjE1g4 --no-auto-check-trustdb --trust-model always --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver keyserver.ubuntu.com --recv-key D284E608A4C46402
gpg: requesting key A4C46402 from hkp server keyserver.ubuntu.com
gpgkeys: key D284E608A4C46402 not found on keyserver
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

and I've tried

$ gpg --keyserver keyserver.ubuntu.com --recv-key D284E608A4C46402'
gpg: requesting key A4C46402 from hkp server keyserver.ubuntu.com
gpgkeys: key D284E608A4C46402 not found on keyserver
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

$ gpg -a --export D284E608A4C46402 | sudo apt-key add -
gpg: WARNING: nothing exported
gpg: no valid OpenPGP data found

I'm behind proxy, and configured /etc/apt/apt.conf and /etc/environment files and aswell exported the proxy setting in terminal, pinging any site from terminal is working.

and still I get the GPG error same as above, can anyone suggest me a solution?

save the whole content of this link in ~/key . Then in terminal, type

sudo apt-key add ~/key

and you should get an OK message.

Further reading: How to remove keys

Open a terminal and use this command:

sudo apt-get install rcn-ee-archive-keyring 

solution courtesy: RobertCNelson