GNUPG has a trust database stored at ~/.gnupg/trustdb.gpg
You can backup this trust database using the --export-ownertrust
option:
gpg --export-ownertrust > file.txt
If you exported your secret keys and import them later into a new environment, the trust database is no longer present.
However, this is easily remedied:
gpg --edit-key [email protected]
gpg> trust
Please decide how far you trust this user to correctly verify other users' keys
(by looking at passports, checking fingerprints from different sources, etc.)
1 = I don't know or won't say
2 = I do NOT trust
3 = I trust marginally
4 = I trust fully
5 = I trust ultimately
m = back to the main menu
Your decision? 5
And don't forget to save the changes:
gpg> save
Read about trust levels and values. E.g. unknown Nothing is known about the owner's judgement in key signing. Keys on your public keyring that you do not own initially have this trust level.