Before diving down the rabbit hole, I do want to start off by saying that the app discussed here are not officially endorsed by the Tor Project. The Onion Browser for iOS is a web browser for iPhone and iPad that encrypts and tunnels traffic through the Tor network. Released in 2012, it has gained more attention recently since its developer Mike Tigas made it free to download on the Apple App Store.
Along with keeping your web traffic “anonymous”, the Onion Browser for iOS allows you to view .onion websites on the dark net from your mobile device. According the developer’s website it also has the added benefits off:
- Fight online tracking: use a new IP address and clear your cookies/history/cache by pressing one button.
- Block third party cookies or all cookies.
- Ability to change cookie storage policy (Allow All / Block Third Party / Block All)
- Disable scripts and multimedia content that can be used to track you.
- Can send the “Do Not Track” HTTP header (DNT: 1) to websites.
Due to limits in iOS set by Apple, it is lacking in some functionality that is available through the desktop Tor Browser. Tigas outlines in a blog post that there are two big challenges in developing and using Tor on iOS. The first is that Apple requires all browsers to use the iOS WebKit rendering engine. Second, is Tor’s inability to be able to run as a system-wide service or daemon on iOS. The end result is to being not as secure as you could be running the full Tor browser.
According to Tigas Apple’s WebKit API’s, “don’t allow a lot of control over the rendering and execution of Web pages, making a Tor Browser-style security slider very difficult to implement.” Other iOS’s multimedia features prevent the browser’s network stack from being used, which in turn makes it difficult to keep network traffic from leaking outside of the Tor network. Lastly, iOS presents more challenges of living in sandbox style operating system. This prevents the Onion Browser from running in the background and routing all your device traffic over Tor.
Having access to Tor via your iOS device is important for those who want to add another layer of security to their mobile communications. Growing global issues are part of the reason that Tigas made the app free to download. He told Ars Technical in a recent interview that, “Iran is not technically a country where you can get an iPhone, but on the grey market you can.” He continued by saying “People over there can’t get apps you have to pay for, because you have to have a credit card that Apple actually accepts.” Using Tor is not the end all be all of security and privacy tools. However, it is useful for those living under oppressive regimes and they can use all the help they can get.