Export existing private ssh key to OpenPGP card or Yubikey
Before you begin
This will only work with OpenPGP v2.0 or newer or with PIV cards. Your existing ssh key has to be in a format that is supported by your opengpg card. For example my the OpenPGP V2.1 Card from FLOSS Shop supports only 2048 bit RSA keys. RSA exponent should be 65537, Putty and old OpenSSH releases use different expnent that for example Yubikey does not support.