In the .gnupg directory there are these files,
(alpha numeric)*.key e.g. 1EFA02EFP.key What are they? Are these v1 gpg key files? And how do i import these?
And where are the private keys held? I see a sshcontrol, tofu.db sqlite3 file, the trustdb.gpg, and pubring.kbx, pubring.kbx~. But where are the private keys written to?
From man gpg of GPG version 2.2.12 (emphasis mine):
--secret-keyring file
This is an obsolete option and ignored. All secret keys are stored in the ‘private-keys-v1.d’ directory below the GnuPG home directory.
So, those *.key files are the actual, current-version secret keys, also known as private keys. In older GPG versions, there used to be secring.gpg corresponding to pubring.gpg, and in GPG 2.1, the private key storage format was changed from a keyring file to a directory of separate key files. At the same time, the public key storage format was changed from a .gpg keyring file to a .kbx keybox file.
To import a secret key to another user's GPG 2.x environment, apparently gpg --import secret.key does the right thing. The tricky part will probably be getting that file securely to the other user.
