Grassroots Distributed Systems for Digital Sovereignty: Concept, Examples, Implementation and Applications

Informally, a distributed system is grassroots if it can have autonomous, independently-deployed instances -- geographically and over time -- that can interoperate once interconnected. An example would be a serverless smartphone-based social network supporting multiple independently-budding communities that merge when a member of one community becomes also a member of another. Grassroots applications are potentially important as they may provide a foundation for digital sovereignty, which we interpret as the ability of people to conduct their social, economic, civic, and political lives in the digital realm solely using the networked computing devices they own and operate (e.g., smartphones), free of third-party control, surveillance, manipulation, coercion, or value-extraction (e.g., by global digital platforms such as Facebook or Bitcoin). Here, we formalize the notion of grassroots distributed systems and grassroots implementations; specify an abstract grassroots dissemination protocol; describe and prove an implementation of grassroots dissemination for the model of asynchrony; extend the implementation to mobile (address-changing) devices that communicate via an unreliable network (e.g. smartphones using UDP); and illustrate how grassroots dissemination can realize applications that support digital sovereignty -- grassroots social networking and sovereign cryptocurrencies. The mathematical construction employs distributed multiagent transition systems to define the notions of grassroots protocols and grassroots implementations, to specify grassroots dissemination protocols and their implementation, and to prove their correctness. The implementation uses the blocklace -- a partially-ordered DAG-like generalization of the blockchain.