A free app for Android, by Angry Robot.

You need a personal diary for those moments when you need to keep some secrets, but do not want to forget them in the future. You can do this with SafeDiary, the perfect journal for all who need a safe place to safely keep their memories. You can securely add information, photos, videos, and even voice notes to your entries. It will keep the details you are not ready to reveal in a safe place, and, of course, store them securely in your Google Drive. It’s a simple yet effective tool for storing data.

The app has a convenient and secure way of keeping your diary. You can choose between two ways of keeping the data: with a password or with a fingerprint. You can also keep a diary for multiple devices.