Gentoo
└─ GnuPG

Creating keys

Follow the Gentoo Infrastructure guide for creating new keys.

SSH

Follow the Gentoo Wiki excerpt for setting up a GPG agent for SSH.

Generate ECC keys, though, as those are much more secure.

Here's a snippet to put into /etc/bash/bashrc:

unset SSH_AGENT_PID
if [ "${gnupg_SSH_AUTH_SOCK_by:-0}" -ne $$ ]; then
    gpgconf --launch gpg-agent
    export SSH_AUTH_SOCK="$(gpgconf --list-dirs agent-ssh-socket)"
fi