Handle gpg keys offline.
The setup described here is currently based on Debian 8 (Jessie).
Download a Debian live image and copy it to your stick:
$ wget http://cdimage.debian.org/debian-cd/current-live/amd64/iso-hybrid/debian-live-8.6.0-amd64-standard.iso
$ sudo cp debian-live-8.6.0-amd64-standard.iso /dev/sdX
$ sudo sync
We use the (commandline-oriented) standard image of Debian.
In case of trouble see https://www.debian.org/releases/stable/amd64/ch04s03.html.en.