Some followup information. The local proxy server was the 3.1.19 package under Ubuntu 12.04. Just for fun, I compiled 3.3.3 and ran that instead. At that point, things worked as expected: curl -v http://keyserver.ubuntu.com * About to connect() to proxy 10.10.10.10 port 3128 (#0) * Trying 10.10.10.10... connected > GET http://keyserver.ubuntu.com HTTP/1.1 > User-Agent: curl/7.22.0 (x86_64-pc-linux-gnu) libcurl/7.22.0 OpenSSL/1.0.1 > zlib/1.2.3.4 libidn/1.23 librtmp/2.3 > Host: keyserver.ubuntu.com > Accept: */* > Proxy-Connection: Keep-Alive > < HTTP/1.1 200 OK < Date: Sun, 07 Apr 2013 00:14:43 GMT < Server: sks_www/1.1.4 < Cache-Control: no-cache < Pragma: no-cache < Expires: 0 < Content-Length: 1417 < Content-Type: text/html; charset=UTF-8 < X-Cache: MISS from localhost < X-Cache-Lookup: MISS from localhost:11371 < X-Cache: MISS from proxy < Via: 1.0 localhost (squid/3.1.19), 1.1 proxy (squid/3.3.3) < Connection: keep-alive And the original apt-key call: /usr/bin/apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 765C5E49F87CBDE0 Executing: gpg --ignore-time-conflict --no-options --no-default-keyring --secret-keyring /tmp/tmp.tEx1FQBbkI --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 765C5E49F87CBDE0 gpg: requesting key F87CBDE0 from hkp server keyserver.ubuntu.com gpg: key F87CBDE0: "RCB Build <rcb-deploy@xxxxxxxxxxxxxxxxxxx>" not changed gpg: Total number processed: 1 gpg: unchanged: 1 I'd still like to understand the original failure under 3.1.19. "Upgrade your proxy" isn't the greatest answer for the next person who stumble across this issue. Thanks! -=Chris -- View this message in context: http://squid-web-proxy-cache.1019090.n4.nabble.com/Local-Squid-to-Reverse-Squid-to-keyserver-ubuntu-com-tp4659400p4659401.html Sent from the Squid - Users mailing list archive at Nabble.com.