Just stumbled over this closed thread here: GPG Error while running apt-get
Same problem here, Ubuntu 12.04 behind a firewall and proxy.
I dont think that matter is duplicate of the given topic. So i reopen this matter in this thread.
My output:
root@musik-Aspire-7741:~# apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 58B98E87
Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret- keyring /tmp/tmp.tWVMhyIMYh --trustdb-name /etc/apt/trustdb.gpg --keyring /etc/apt/trusted.gpg --primary-keyring /etc/apt/trusted.gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 58B98E87
gpg: Key 58B98E87 of hkp Server keyserver.ubuntu.com request
?: keyserver.ubuntu.com: Connection refused
gpgkeys: HTTP fetch error 7: couldn't connect: Connection refused
gpg: No valid OpenPGP data found.
gpg: Total number processed: 0
Conclusion: gpg is not working with hkp://keyserver.ubuntu.com:80
via http.
http_proxy
set? (echo $http_proxy
)