This tutorial series will teach you how to use GPG (Gnu Privacy Guard) in the Linux terminal, so you will be able to send encrypted email messages and digitally sign documents.

A Practical Guide to GPG Part 2: Public Key Management
https://www.linuxbabe.com/security/gpg-guide-public-key-management

A Practical GPG Guide Part 3: Encrypt and Decrypt Files
https://www.linuxbabe.com/security/gpg-encrypt-and-decrypt-message

How to configure GPG in the Thunderbird email client
https://www.linuxbabe.com/security/encrypt-emails-gpg-thunderbird

A Practical Guide to GPG Part 5: Digital Signature
https://www.linuxbabe.com/security/gpg-digital-signature

How to Verify PGP Signature of Downloaded Software on Linux
https://www.linuxbabe.com/security/verify-pgp-signature-software-downloads-linux