Today I tried to update my arch box and got the following error
error: confuse: signature from "Thorsten Töpper <atsutane@freethoughts.de>" is unknown trust
I have fixed it with following command
sudo pacman-key --refresh-keys
If you want to add specified key use following command
gpg --keyserver hkp://keys.gnupg.net:80 --recv-keys C1A60EACE707FDA5