Some people suggest it is because of the DNS and to use --no-check-certificate with wget. Others suggest updating the keyserver:
root@OpenWrt:~# gpg --verbose --keyserver hkp://keys.opengp.org --refresh-keys
root@OpenWrt:~# gpg --keyserver 'keys.openpgp.org' --recv-key '28645AC9776EC4C00
BCE2AFC0FE641E7235E2EC6'
gpg: requesting key 235E2EC6 from hkp server keys.openpgp.org
gpgkeys: key 28645AC9776EC4C00BCE2AFC0FE641E7235E2EC6 can't be retrieved
I don't think the first command did anything