CryptSync is an opensource encryption and synchronization tool which allows you to fully encrypt and compress your files and folders to store on your favorite cloud service. Weather it is SkyDrive, DropBox or Google Drive, you can be assured your files will always be stored encrypted so that no one, not even the cloud service providers could see your files, protected even if they get hacked. Just make sure you use a different password to encrypt your data with CryptSync other than the one you use with your cloud storage provider. You can also backup and encrypt your files to more than one cloud storage: just set up two sync pairs with the original folder being the same for both pairs.
CryptSync works by synchronizing folder pairs. One folder is called the original folder: that’s where your unencrypted files are stored and where you work with your files. The second folder of such a pair is the encrypted folder which is where the files get copied from the original folder and encrypted. The encrypted folder is usually located somewhere inside your cloud storage sync folder.
The encryption is done using 7zip, which will also compress them at the same time. That means you not only get 256bit AES encryption but also compression for free, which reduces the storage space you use in the cloud.
That also means that if you ever need to access your encrypted files directly from the cloud, you can save them locally and just open them with 7-Zip or other compression tools. Of course you’will then be asked to provide the password you used with CryptSync to open that file. If you have an Android phone, you can use apps like ZArchiver to access your encrypted files on the go.
Optionally the encryption can be done using GnuPG. Please note that when using this option, the encrypted files can be larger than the original files and use up more space on your cloud drive.
When you first start CryptSync, the main dialog is shown where you have to set up the folders to synchronize. The Original folder is the folder you store and work with your private documents, pictures etc. Encrypted folder should be the folder you specified with the cloud service to sync from. Also notice the option to Encrypt filenames. If this option is checked all filenames on the cloud server will be encrypted as well. This is a an extra level of protection which would make even the filenames useless to an attacker or innocuous in a data-breech. Just realize if you plan on accessing these files from your phone, you will not be able to read the filenames. They will be seen like in the second image below.
Encrypted File Names:
Review and Create more Sync Pairs
After your folders are setup and encryption option chosen, you can now review your sync pairs, create a new sync pair, choose to start the CryptSync with Windows, ignore specific files and extensions. Also choose how often you want CryptSync to scan your sync folders for changes. When files have been added or changed, CryptSync will encrypt and sync the new files to the cloud synced folders automatically.
There is other software available which does this same task but they are usually closed source and cost money, like Boxcryptor and Viivo. A free and opensource alternative to CryptSync, available on Windows, Mac and Linux is: Cryptomator. If you use any type of cloud service you need to encrypt the files you store there. It is just a matter of time until those files are hacked or employees of those services view your files.