After many requests from several users and after many months of promise, the Dotdeb repositories are GPG-signed. Yes, you can now get rid of the annoying “WARNING: The following packages cannot be authenticated!” message!
Waiting for a dotdeb-keyring package, you just have to get the key and add it to your trusted keys’ keyring :
gpg --keyserver keys.gnupg.net --recv-key 89DF5277 gpg -a --export 89DF5277 | sudo apt-key add -
I hope you’ll enjoy it.