Install caja-seahorse by entering the following commands in the terminal:
sudo apt update sudo apt install caja-seahorse
Caja extension to encrypt/decrypt OpenPGP files using GnuPG
Seahorse caja is an extension for caja which allows encryption and decryption of OpenPGP files using GnuPG. It is integrated into the caja right-click menu, but can also be used from the command line. It's based on seahorse-nautilus.