If you are using the [debian repository] at repo.mosquitto.org you may have noticed that the repository signing key expired at the end of 2017. To get the updated key use the following commands: ``` wget http://repo.mosquitto.org/debian/mosquitto-repo.gpg.key sudo apt-key add mosquitto-repo.gpg.key ``` [debian repository]:/blog/2013/01/mosquitto-debian-repository