DroidFS

DroidFS is an alternative way to use encrypted overlay file-systems on Android that uses its own internal file explorer instead of mounting volumes. This allows you to store files in encrypted vaults that other apps can't decrypt.
Currently, DroidFS supports the following encrypted containers:
• gocryptfs (https://github.com/rfjakob/gocryptfs): encrypts file contents and file names but doesn't hide directory structure or file sizes.
• CryFS (https://github.com/cryfs/cryfs): slower, but encrypts everything and obfuscates file sizes.

Features:
• Compatible with original encrypted volume implementations
• Internal support for video, audio, images, text and PDF files
• Built-in camera to take on-the-fly encrypted photos and videos
• Ability to expose volumes to other applications
• Unlocking volumes using fingerprint authentication
• Volume auto-locking when the app goes in background

Permissions:
Read & write access to shared storage: required to access volumes located on shared storage.
Biometric/Fingerprint hardware: needed to encrypt/decrypt password hashes using a fingerprint protected key.
Camera: required to take encrypted photos or videos directly from the app.
Record audio: required if you want sound on videos recorded with DroidFS.
Notifications: used to report file operations progress and notify about volumes kept open

All of these permissions can be denied if you don't want to use the corresponding feature.

DroidFS is free, open-source, and you can find the project's repository:
• on GitHub: https://github.com/hardcore-sushi/DroidFS
• on Tangled: https://tangled.org/cipherd.arkensys.dedyn.io/DroidFS

Warning !
Security is neither absolute nor definitive. DroidFS does not come with any warranty and should not be considered as an absolute safe way to store files.