Using launchpad PPA behind proxy

I was trying to setup my Ubuntu VM in work machine and I was trying to install Chromium-daily build ppa from launchpad. I have global proxy setup in my account but when I tried to setup the PPA it was not working. So standard method

sudo apt-add-repository ppa:your-ppa

was not working. The alternative was to manually set repository and authenticate the repo via 'apt-key' as shown below:

Step 1: Add the repository via 'apt-add-repository' without authenticating its GPG key.

sudo apt-add-repository 'deb http://ppa.launchpad.net/gwibber-daily/ppa/ubuntu jaunty main'

Here replace the repository info.

Step 2: Authenticate the repository using 'apt-key'. First get the PPA key info from its web page. For Chromium-daily build the key is 4E5E17B5. Use following command to authenticate using http-proxy settings of your machine.

sudo apt-key adv --keyserver keyserver.ubuntu.com --keyserver-options http-proxy="http://your.proxy.server" --recv-keys 4E5E17B5

If things goes well then you will see a message from gpg saying 'Total number processed: 1' and you should be able to install your software from either Synaptic or Ubuntu-Software-Center.