Install kleopatra by entering the following commands in the terminal:
sudo apt update sudo apt install kleopatra
Description:
Certificate Manager and Unified Crypto GUI
Kleopatra is a certificate manager and a universal crypto GUI. It supports managing X.509 and OpenPGP certificates in the GpgSM keybox and retrieving certificates from LDAP servers.
Homepage: https://www.kde.org/applications/utilities/kleopatra/
Version: 4:17.12.3-0ubuntu1
Section: universe/net