since the internet is full of outdated information on configuring the Yubikey to work with GnuPG on macOS I'll get you an update for High Sierra.
Personally I'd recommend to use
GPG Suite from https://gpgtools.org/ to install
gnupg on a macOS. It brings a lot of features and a plugin for Mail.
Use Yubikey's OpenPGP with SSH
gpg-agent.conf config and update your
~/.bash_profile to enable gnupg's ssh agent.
pinentry-program /usr/local/MacGPG2/libexec/pinentry-mac.app/Contents/MacOS/pinentry-mac default-cache-ttl 600 max-cache-ttl 7200 enable-ssh-support
just update the ttl's if you want different ones
# on OS X with GPGTools, comment out the next line: #eval $(gpg-agent --daemon) GPG_TTY=$(tty) export GPG_TTY if [ -S "$HOME/.gnupg/S.gpg-agent.ssh" ]; then export SSH_AUTH_SOCK="$HOME/.gnupg/S.gpg-agent.ssh" fi
If you installed gnupg via
gpgtools.org's GPG Suite you don't need to worry about starting the daemon. It gets automatically installed. If you used
brew or something else you might need to uncomment the
eval line and start the gpg-agent daemon