Software can let smartphones, Wi-Fi routers, and other hardware link up without centralized Internet service.
After an earthquake crippled Haiti in 2010, killing and injuring hundreds of thousands and destroying the country’s communication networks, Paul Gardner-Stephen found himself thinking about all the cell phones that had instantly become useless. With cell towers out of commission across the country, they would be unable to operate. “If the software on the phones was right,” he says, “they would keep working for at least localized communication, handset to handset.”
Gardner-Stephen, a research fellow at Flinders University in Adelaide, Australia, now leads a project that enables Android phones to do just that. Serval, as the project is called, offers an app that allows nearby phones to link up using their Wi-Fi connections, as long as they have been modified to disable the usual security restrictions. Voice calls, text messages, file transfers, and more can take place between devices with the Serval app installed. Devices don’t need to be in range of one another to communicate, as long as there are other devices running the app in between; data can hop between any phones with Serval installed.
This approach, known as mesh networking, is not a new idea (see “Automatic Networks”). But the combination of relatively cheap smartphones and Wi-Fi routers with the progress made by open-source projects such as Serval means that creating and operating such networks is now becoming possible without specialist knowledge.
“We’re trying to dramatically increase the usability and take this out of the geekosphere,” says Sascha Meinrath, the leader of a project called Commotion Wireless, which is developing several software packages that allow people to create mesh networks using low-cost Internet and networking hardware, primarily Wi-Fi routers. The Commotion project is run by the Open Technology Institute, an initiative of the New America Foundation, a nonpartisan think tank in Washington, DC.
Some communities in Washington, Brooklyn, and Detroit already have Wi-Fi-based mesh networks built on Commotion’s technology. The networks offer free Internet access by extending the reach of free connections offered by community centers; they also provide Web services and apps that function only within the local mesh.
After superstorm Sandy cut power to most of Red Hook, Brooklyn, the neighborhood’s mesh network demonstrated how the technology could help recovery after natural disasters. A FEMA-provided satellite Internet link was connected to one part of the Commotion-based network still operating, and a mesh-enabled Wi-Fi router was installed on the roof of an auto body shop that also still had power. That made it possible for many residents and the local aid distribution point to use the slow but badly needed satellite link.
News from the Middle East in recent years—and the U.S. in the past few weeks—has also raised awareness of the potential for mesh networks to create communication networks independent of government oversight. Voice calls and text messages made using phones on a Serval mesh network are strongly encrypted. Gardner-Stephen says that smartphones with Serval installed could enable, say, protesters to keep reaping the benefits of those devices even if cellular networks are shut off.
“You could have someone taking pictures and video at a protest and sharing them immediately to the mesh,” he says. “Even if that person’s phone is seized, the footage has already made it to 10 other phones in the area, and then to hundreds or thousands more.” If one of those people had access to a satellite link, the world would soon know what had happened, he says.
The Commotion project is also working on making its mesh software useful to people, such as political dissidents, for whom conventional connectivity isn’t safe, and the project has received federal grants to support that work. “The State Department and USAID are interested in protecting the free flow of information,” says Meinrath. “You could use a mesh to route around surveillance and censorship.”
To that end, the Commotion team is adapting an encrypted chat program called Cryptocat so it can be used to communicate securely across a local mesh network. Another adaptation aims at making it possible to route communications only through trusted devices on a mesh network, in case an adversary has joined and is collecting traffic. However, Commotion’s security features are far from complete, and the project prominently displays a warning label on its site to indicate its current limitations.
The range of Wi-Fi poses a technical challenge for mesh networks. Tests by the Serval project indicate that for two phones to communicate directly over a Wi-Fi mesh, they need to be within 100 meters of one another with a clear line of sight, or about a room away if they’re linking through buildings.
Serval is currently testing a device called a mesh extender that can help networks based on its technology reach farther. The device uses Wi-Fi to connect tens of nearby Serval devices to a long-range radio link. If extenders are mounted on the roof, links between several of them should be able to stretch kilometers, says Gardner-Stephen. A crowdfunding campaign to support development of a production version of his prototype will launch soon, and the New Zealand Red Cross is helping test the current design.