Thanks (or no thanks) to Edward Snowden, people have become more aware of problems with communication security. "Backdoors" on devices have been scrutinized but there is still much to be done. For now, iPhone users have Signal.
Developed by Open Whisper Systems, Signal is an iPhone app that makes it possible for users to make calls worldwide that are free of charge and encrypted. The app was built upon the ZRTP protocol created by Phil Zimmerman and rolled out with AES128. In theory, this ZRTP-AES128 combo is good enough to deal with all known practical attacks by anyone from hacking noobs to the NSA.
Using an existing number, Signal does not need a password to be used. It simply goes through contacts in a secure manner, immediately displaying which of the user's contacts are using the app as well so calls can be made immediately. It also takes advantage of a jiffy buffer tuned to mobile networks, turning to push notifications to minimize battery use without sacrificing response sensitivity.
Signal is easy to use because Open Whisper Systems wants the app to be actually used.
"In many ways the crypto is the easy part," he says. "The hard part is developing a product that people are actually going to use and want to use. That's where most of our effort goes," explained Open Whisper Systems founder, Moxie Marlinspike.
For those who don't want to take Open Whisper Systems' word on security, it is possible to check Signal's code because it is running on open source software. Interested parties are also encouraged to help improve the app, with the developer paying out a portion of the donated Bitcoins it receives for each merged pull request.
Aside from Bitcoin donations, Open Whisper Systems is also funded by government grants. Doesn't this go against what it's working on? The company argues that the agencies from which it receives funding do not control what Open Whisper Systems develops and that it is more concerned about what it can do to make the U.S. as free from self-censorship as possible.
Signal aims to be a unified communication platform not just for the iPhone but including Android and browsers as well. The iPhone app is expected to expand support for text messages later in the summer and compatibility with TextSecure for Android is assured. Open Whisper Systems is also working on combining RedPhone and TextSecure as well to create Signal for Android.
Signal for iPhone was developed with the help of Twisted Oak Studios. Tyler Reinhard provided the design for the app.
