  Blockchain, also coined as decentralized AI, has the potential to empower AI
to be more trustworthy by creating a decentralized trust of privacy, security,
and audibility. However, systematic studies on the design principle of
blockchain as a trust engine for an integrated society of
cyber-physical-social-system (CPSS) are still absent. In this article, we
provide an initiative for seeking the design principle of blockchain for a
better digital world. Using a hybrid method of qualitative and quantitative
studies, we examine the past origin, the current development, and the future
directions of blockchain design principles. We have three findings. First, the
answer to whether blockchain lives up to its original design principle as a
distributed database is controversial. Second, the current development of the
blockchain community reveals a taxonomy of 7 categories, namely, privacy and
security, scalability, decentralization, applicability, governance and
regulation, system design, and cross-chain interoperability. Both research and
practice are more centered around the first category of privacy and security
and the fourth category of applicability. Future scholars, practitioners, and
policy-makers have vast opportunities in other, much less exploited facets and
the synthesis at the interface of multiple aspects. Finally, in
counter-examples, we conclude that a synthetic solution that crosses discipline
boundaries is necessary to close the gaps between the current design of
blockchain and the design principle of a trust engine for a truly intelligent
world.
