Originally Posted by waterhead
To actually add the key to your system, run this command.
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys CEC06767
that's what i was going to say , i fllowed this steps ( on the site) :
How do I use software from a PPA?
To start installing and using software from a Personal Package Archive, you first need to tell Ubuntu where to find the PPA and how to verify the authenticity of its software.
Adding the PPA to Ubuntu
Step 1: Copy the first line from the apt sources.list entries section of the PPA overview page. For example:
Step 2: On your Ubuntu computer, open System > Administration > Software Sources.
Step 3: Click the Third Party Software tab.
Screen shot of the top tabs in the Software Sources app
Step 4: Click the Add button.
Step 5: Paste the line you copied in step 1 and click the Add Source button.
Step 6: Now copy the second line from the apt sources.list entries section of the PPA overview page and paste it in just as you did in steps 4 and 5.
When prompted, reload the software sources information. Don't worry if you see a warning about unverified software sources; we're going to fix that next.
Telling Ubuntu how to authenticate the PPA
Now Ubuntu knows about the PPA. It also needs to know how to check the software hasn't been tampered with since Launchpad built it.
Note: This is not an endorsement of any of the software in PPAs. You must make sure you trust the PPA owner before installing their software.
Step 1: On the PPA's overview page you'll see the PPA's OpenPGP key id. It'll look something like this: 1024/12345678. Copy it, or make a note of, the portion after the slash, e.g: 12345678.
Step 2: Open your terminal and enter:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 12345678
Replace 12345678 with the key id you copied in step 1.
Step 3: Finally, tell Ubuntu to re-load the details of each software archive it knows about
sudo apt-get update
You're now ready to install software from the PPA!