How Hong Kong protestors use mesh networks to send messages without the internet
For the past few months, Hong Kong protestors have been using San Francisco startup Bridgefy’s mesh-network messaging app to communicate without using the internet.
The app allows users to send messages to each other via a Bluetooth mesh network, bypassing the danger of the internet, where communications can potentially be monitored by authorities and used to identify and track down protest leaders. The move to mesh networks also insures against the possibility of a government shutdown of internet service to the city.
How does mesh network messaging work, exactly? Between two users in close proximity, this is simple: messages are sent directly from one device to the other via Bluetooth. However, if there is a chain of app users, each user within close proximity to the next, then messages can hop from one device to the next and reach users relatively far away. With a large and geographically dense enough group of users, all of these Bluetooth connections form a thorough network, enabling messages to be sent all the way from one end of the city to another by hopping between devices, never once diverting to an external server.
The operation of a mesh network depends directly on the number of people who use it. This is a simple example of network effects in play. In the seven days prior to the publishing of the linked article, the Bridgefy was installed more than 60,000 times, mostly in Hong Kong. The reason why the app found such widespread success in the city was because protestors expected many other people to also install the app. With many people using the app, the mesh network becomes extensive and dense, allowing distant and rapid transmission of messages. If protestors didn’t expect the app to be popular, there would be little reason to download it, because with few users, the mesh network would be sparse and messages wouldn’t be able to travel very far or to very many people.
The use of mesh networks for protest organization isn’t new; another app, FireChat, has been used by protestors in Taiwan, Iran, and Iraq, as well as in Hong Kong’s earlier 2014 protests.