Enhancing Blockchain-Based Processes with Decentralized Oracles

The automation of business processes via blockchain-based systems allows for trust, reliability and accountability of execution. The link that connects modules that operate within the on-chain sphere and the off-chain world is key as processes often involve the handling of physical entities and external services. The components that create that link are named oracles. Numerous studies on oracles and their implementations are arising in the literature. Nevertheless, their availability, integrity and trust could be undermined if centralized architectures are adopted, as taking over an oracle could produce the effect of a supply-chain attack on the whole system. Solutions are emerging that overcome this issue by turning the architecture underneath the oracles into a distributed one. In this paper, we investigate the design and application of oracles, distinguishing their adoption for the in-flow or out-flow of information and according to the initiator of the exchange (hence, pull- or push-based).