On Wed, 19 Dec 2018 at 11:26, Arnd Bergmann <arnd@arndb.de> wrote:

- Make sure that you have a valid GPG key, with at least 2048 bits.
If you don't have one, create a fresh RSA-4096 key as documented

There's a fairly good key creation guide here: https://keyring.debian.org/creating-key.html