This app does not claim any permissions, so you can trust that it cannot send any of your private data to anyone. Messages produced by this app are secure and, for example, can be confidently sent over a network. It uses AES in GCM mode with no padding for encryption. It uses Argon2 and a random Salt to derive a secure key from the entered passphrase. This is a very powerful encryption. It also encrypts its settings before storing them on the device. However, the app might be vulnerable to some attacks. Although it is secure enough to stand attacks from non-expert crackers, e.g. normal users, should not be used for serious data encryption. <b>Upgrading from 4.x to 5.x</b> The encryption of the settings is changed. The app should be able to detect the old settings and upgrade them with the new encryption algorithm. However, it's a good idea to <b>back-up your passphrase</b>. (Well, it's generally a good idea to back-up encryption keys and passwords in a secure place). If the app didn't work after upgrade, uninstall and install it again.