Evidence-Based Oracles Using Bayesian Network

A blockchain oracle is a service that 'feeds' a smart contract with data from the off-chain world; in other words, it is a bridge between the off-chain and on-chain worlds. The main limitation of oracles is that the smart contract that receives data from an oracle has no guarantee that the data is reliable and, therefore, must trust it. Several solutions have been proposed recently to what has been called the 'oracle problem'. A limitation of these solutions is that they focus on how trustworthy the oracle is, and the solutions lack generality. The main original contributions of this work are: (1) An approach is proposed that focuses on the trustworthiness of the data, rather than of the oracle, by relying on the evidence collected to support the truth of such data. (2) The relationship between the evidence and the data has been formalized using Bayesian networks. (3) Bayesian networks have been implemented on smart contracts.