{myvars, ...}: {
  programs.ssh = myvars.networking.ssh;

  users.users.${myvars.username} = {
    description = myvars.userfullname;
    # Public Keys that can be used to login to all my PCs, Macbooks, and servers.
    #
    # Since its authority is so large, we must strengthen its security:
    # 1. The corresponding private key must be:
    #    1. Generated locally on every trusted client via:
    #      ```bash
    #      # KDF: bcrypt with 256 rounds, takes 2s on Apple M2):
    #      # Passphrase: digits + letters + symbols, 12+ chars
    #      ssh-keygen -t ed25519 -a 256 -C "ryan@xxx" -f ~/.ssh/xxx`
    #      ```
    #    2. Never leave the device and never sent over the network.
    # 2. Or just use hardware security keys like Yubikey/CanoKey.
    openssh.authorizedKeys.keys = myvars.mainSshAuthorizedKeys;
  };
}
