Centralized Systems

Chakraborty, Pranab; Maitra, Subhamoy; Nandi, Mridul; Talnikar, Suprita

Digital Contact Tracing (DCT) protocols and systems usually rely on close-range communications between handheld devices (like smartphones and tablets), primarily through a Bluetooth Low Energy (BLE) interface and a client-server mode of communication between the apps installed on the devices and the backend server(s). Depending upon the role played by the backend server(s), DCT protocols and systems are usually classified as centralized or decentralized. In Chap. 10.1007/978-981-15-9727-5_1, we have discussed some of the competing ways of classifying systems, eventually settling with the following broad-level understanding: for the scope of this book, we shall consider a system (or a protocol) centralized if the backend server(s) plays (or play) a dominant role in deciding the risk level (or risk-score) of an individual being infected. This chapter focuses on centralized systems and protocols like BlueTrace, TraceTogether, COVIDSafe, ROBERT etc. It also presents a generalized framework of centralized systems before going deep into the specific systems. The chapter ends with discussions on systems that lie in between the centralized and decentralized categories, thus setting the stage for decentralized systems in Chap. 10.1007/978-981-15-9727-5_3.