Door Advanced Encryption Standard:
Ik zou eerst de passphrase van je secret key halen. Want daar kan de OpenPGP implementatie van Thunderbird (RNP) niet mee omgaan.
Daarna kan je de secret key exporteren met dit commando:
--export-secret-keys
--export-secret-subkeys
Same as --export, but exports the secret keys instead. The exported keys are written to STDOUT or to the file given with option --output. This command is often used along with the option --armor to allow for easy printing of the key for paper backup; however the external tool paperkey does a better job of creating backups on paper. Note that exporting a secret key can be a security risk if the exported keys are sent over an insecure channel.
The second form of the command has the special property to render the secret part of the primary key useless; this is a GNU extension to OpenPGP and other implementations can not be expected to successfully import such a key. Its intended use is in generating a full key with an additional signing subkey on a dedicated machine. This command then exports the key without the primary key to the main machine.
GnuPG may ask you to enter the passphrase for the key. This is required, because the internal protection method of the secret key is different from the one specified by the OpenPGP protocol.
Bij Thunderbird is het nog mogelijk om een Smartcard te gebruiken door RNP uit te schakelen via een setting in Thunderbird. Dan denk ik dat je meer kans maakt.
Ik snap niet waarom ze niet gewoon GnuPG 2.2 hebben gebruikt. Daar is tenminste goed naar gekeken door experts. RNP is duidelijk nog niet af.