pgp two factor authentication 3

https://extra-wiki.win/index.php/How_to_Complete_Your_Fawkes_Market_PGP_Setup_for_Safer_Darknet_Transactions

Using PGP for two factor authentication isn't really standard, but I've seen people combine GPG keys with a time-based one-time password app for extra security when signing commits or emails. It's a bit of a manual setup, but it adds another layer beyond just your private key passphrase.