Abstract: The oracle is the interface between the blockchain and the external data exchange. It is responsible for the ordering of the input data and the data consistency transaction session. However, the security of oracle, a centralized blockchain system component, is not protected by the security mechanism of the blockchain system. After the oracle fails, its input data and transaction process will be lost. In order to avoid the loss caused by the failure of the oracle, in this paper, we propose a novel fault-tolerant oracle software architecture of blockchain. Specifically, we design the reliability evolution requirement model and the intelligent fault-tolerant evolution model. By leveraging these two models, the security mechanism of the oracle is improved. Furthermore, we propose the corresponding evolution algorithms to enable the automatic fault-tolerant evolution of the software architecture after the oracle fails. In experiments, we employ the virus attack case to verify the novel oracle reliability and also we evaluate the fault-tolerant evolution cost, backup oracle replacement timing respectively. Extensive experimental results show the practical value and effectiveness of the proposed fault-tolerant oracle software architecture and its evolution algorithms.

Key words: blockchain, oracle, fault tolerance, neural network, software evolution