Today we had a problem at work on a system. Without getting into too much detail as to give away secrets behind the verbal NDA I am behind, I will just say that it had to do with a GPG public key of mine that was expired on a dev machine, accidentally propagating during install to a production machine. This key had a sub key as well, so figuring out this was tricky.

To start, you can list your gpg keys like so:

$ gpg --list-keys

This will list keys such as

pub 4096R/01A53981 2011-11-09 [expires: 2016-11-07]
uid Tyrel Anthony …