Onionshare is a free open source program for Windows, Mac OS X and Linux that enables you to transfer files security using Tor.
File sharing has not changed all that much in the past ten or so years. You can send files to other users in various ways: using email, (s)ftp, file sharing services, or online storage services. There are a couple of other options such as sharing files using USB storage devices and face to face exchanges.
It is difficult to transfer files securely. You could encrypt files before you send or upload them, but someone listening in could dump the data and try to break the encryption.
Face to face may work best, but only if you are not crossing any borders.
Onionshare was designed as a direct response to a passage in Glenn Greenwalds new book in which he described the issues that he was facing getting Snowden file copies from a fellow journalist.
The open source program Onionshare uses the Tor network for anonymity. What happens in the background is the following:
When you want to share files, Onionshare creates a temporary password protected website that is hosted on the Tor network.
Anyone with knowledge of the URL and the password can access the data, and download it to a computer system. Onionshare does not take care of that part of the communication though, so it is up to the user who set up the file transfer to use a secure channel to inform recipients about the availability of the data.
The recipient opens the URL in the Tor browser, and downloads files hosted on it to the local system. All that is left to do afterwards is to close down the site. This happens automatically by default after the first download.
You may stop this from being the case though if multiple users need to download the file, or if you want to keep it available in case it needs to be downloaded again.
The program — we have tested the Windows version — is easy to use. You need to install it on your system, and may launch it right after installation.
Note: You need to run Tor Browser on your system. If you don’t have it, download it from the official Tor Project website.
The interface supports drag and drop operations, but you may also hit the add files or add folder button instead to use the file browser. Hit the “start sharing” button afterwards, and wait for the program to create the site in the background. If things go well, you get a custom URL the files or folders you selected are made available on.
Anyone with the url may download those then using Tor.
Passwords are not set up by default. To set up one, click on File > Settings. There you need to switch either to connect using control port, or connect using socket file. The password authentication option becomes available immediately afterwards.
Onionshare is an easy to use, yet anonymous cross-platform file transfer program. You can increase the protection beyond just requiring a password to download the files by encrypting the files.