Cryptomator

What it's for: Cryptomator lets you make encrypted versions of folders and files suitable for storage in the cloud, so that services such as Dropbox, Google Drive, Box.com, OneDrive and others aren't able to read the contents of your files. Cryptomator is therefore a privacy-protecting app, and should be of interest to everyone wishing to keep their private files private in an age of mass surveillance and companies mining our data.

Why Cryptomator is good:

• open source
• no subscriptions/fees - just download and use
• works on Windows, Mac and Linux (coming soon to mobile – Android is in beta)
• simple to use
• encrypts using the very strong AES-256 encryption standard
• minor changes to a file are reflected in the encrypted version and can be synced (not possible with Truecrypt/Veracrypt)
• there are very few apps that do this, and they aren't open source and/or as user-friendly
• the creators reply to forum posts, support tickets and even emails
• it's a huge money saver: using Cryptomator + pCloud/Seafile.de/NextCloud costs MUCH less than Tresorit or SpiderOak.

How Cryptomator works: In the app you create a "Vault" which is just a folder that will contain encrypted versions of your files and a keyfile. You select a (hopefully very strong) password for the Vault. You choose where you want to save the Vault on your computer. This is the folder you should tell your sync service to sync. When you open the Vault by typing in the password, the decrypted version shows up in your browser mounted as a webdav folder, or "virtual hard drive". You put your files in there. Cryptomator encrypts them in real time. If you look in the encrypted version of the folder, you just see gibberish, which is all your sync service can see. Then, you go to another computer (if you like) and you download your encrypted files. You open Cryptomator, choose the keyfile from the synced folder. You enter your password and - again - the decrypted version appears in your browser as a webdav folder in and out of which you can save things. You can even have a Vault open on who machines and the encrypted versions will sync in real time and Cryptomator will decrypt the differences in real time. You can have as many such Vaults as your heart desires, all with different passwords.

Some minor limitations:

1. Only encrypted files available via your browser (e.g. by logging into Dropbox via the browser) But that's a good thing: Dropbox (or Google Drive, etc), their employees, govt agencies or hackers who break into your account won't know what you're storing.
2. Currently, Cryptomator uses Webdav for showing files in your virtual hard disk. A handful of Linux file browsers don’t like this, but you can simply install and use another until Cryptomator switches to FUSE (which they will).
3. File and folder names/structures are encrypted, but not file sizes. But for the level of privacy you get for free via an open source app, you can probably live with that.

According to this Github ticket, Cryptomator is open-source only for the desktop app. The mobile projects do not have available source code.

https://github.com/cryptomator/cryptomator-android/issues/36

[Edited by flosspop, December 11]