- YES - Bluetooth based solutions: it is hardware embedded in all the smartphones, designed to connect devices mostly in a short range, about 5-10 meters (e.g. headphones, car infotainment, wearables). Ideally, if all the devices are both signaling their presence and scanning the presence of others, they could succeed in logging the people you really got close to. The ”Low Energy” version of Bluetooth is also very diffused, and wouldn’t affect the batteries lifecycle. What’s more, the intensity of the radio signal is calibrated (enough) to distinguish the proximity with a resolution of about 4 meters: obstacles in the between, like a wall, would even make the contacts seem less close, helping us to disambiguate the contagion probability. The privacy profile here is still hot, despite it doesn’t imply a geographical location. But still leaves the control of data flows to the individuals: you can stop signaling yourself, and any previous log would never leave your phone.

It definitely seemed the right technology for the solution we had in mind.

- YES - Distributed computing, no central identities DB: architecture would need to ensure two key elements: scalability and privacy. After some brainstorming and thinking, we agreed on a distributed computing architecture as an ideal solution. All the information should be processed on the citizens’ app and device. A central node would function as a broadcaster and would send notifications, but all individuals’ information and logs of connections stays on each users’ device. This solution would keep privacy safe and reduce dramatically the amount of data the central node and devices need to constantly exchange. Thus, it reduces running and scalability costs.