Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
VeraCrypt - VeraCrypt is a free open source disk encryption software for Windows, Mac OSX and Linux.
SMS Plus - SMS Plus app offers features that let you forward text messages through internet connection as well as through other social media platforms.
Axcrypt - AxCrypt - Password Protect Files With Strong Encryption. AxCrypt is the leading open source file encryption software for Windows.
NetSfere Secure Messaging - NetSfere Secure Messaging is a secure messaging app that enables you to send messages by using 256-bit device-to-device encryption features.
Windows BitLocker - This topic provides a high-level overview of BitLocker, including a list of system requirements, practical applications, and deprecated features.