How to create a SSH key.
TMPDATE="$( printf '%(%Y%m%d-%H%M%S)T\n' -1 )"; ssh-keygen -a 100 -t ed25519 -f "${HOME}/.ssh/id_ed25519-${USER}-${HOSTNAME:-$(hostname)}-${TMPDATE}" -C "$USER@${HOSTNAME:-$(hostname)}-${TMPDATE}";
ssh-keygen -t rsa -b 4096 -f ~/.ssh/id_rsa -C "$USER@${HOSTNAME:-$(hostname)}"
~~DISCUSSION~~