Excerpt from a MacPaw blog post dated 2016-04-29:
"[W]e made Encryptor, the engine we built to power our Encrypto app, open-source for developers and anyone interested. Why? Because one, we believe data protection tools should be widely available and easy to make. And two, we think people have the right to know how apps that handle their private files actually work.
So, fellow developers — go ahead and use our code to build your own encryption apps. Our beloved users — go ahead and look what Encrypto has under the hood. You can get Encryptor here on GitHub < https://github.com/MacPaw/ENCryptor >, along with installation and usage instructions. Enjoy!"
The GitHub repository includes a CLI tool called "encrypto-cli" which can encrypt, decrypt, and preview files.
I have successfully tested Encrypto under OS X 10.9.5 and Windows 8.1, encrypting and decrypting files between the two platforms.
Why 4 stars instead of 5?
1. Encrypto for OS X is available only via the Mac App Store, while the Windows version can be downloaded directly. Given the recent problems with MAS, a direct download for OS X is critical if Encrypto is to be relied on.
2. Since Encrypto is free for both OS X and Windows, why not open source the client software and not just the engine? What advantage is there to keeping freeware closed source?