After the private keys are on the Yubikey, they are not exportable. What you can export are secret key stubs , which practically only say this key is on a smartcard. They were the main method of making the key work on a different computer (with the smartcard), but these days, as there is sufficient information stored about the key, all you need is to use --card-status to fetch the same stub from the hardware key, and import the public key.