The adoption of permissioned blockchain networks in enterprise settings has seen an increase in growth over the past few years. While encouraging, this is leading to the emergence of new data, asset and process silos limiting the potential value these networks bring to the broader ecosystem. Mechanisms for enabling network interoperability help preserve the benefits of independent sovereign networks, while allowing for the transfer or sharing of data, assets and processes across network boundaries. However, a naive approach to interoperability based on traditional point-to-point integration is insufficient for preserving the underlying trust decentralized networks provide. In this paper, we lay the foundation for an approach to interoperability based on a communication protocol that derives trust from the underlying network consensus protocol. We present an architecture and a set of building blocks that can be adapted for use in a range of network implementations and demonstrate a proof-of-concept for trusted data-sharing between two independent trade finance and supply-chain networks, each running on Hyperledger Fabric. We show how existing blockchain deployments can be adapted for interoperation and discuss the security and extensibility of our architecture and mechanisms.

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In this paper, we design and implement the first-ever decentralized replicated relational database with blockchain properties that we term blockchain relational database . We highlight several similarities between features provided by blockchain platforms and a replicated relational database, although they are conceptually different, primarily in their trust model. Motivated by this, we leverage the rich features, decades of research and optimization, and available tooling in relational databases to build a blockchain relational database. We consider a permissioned blockchain model of known, but mutually distrustful organizations each operating their own database instance that are replicas of one another. The replicas execute transactions independently and engage in decentralized consensus to determine the commit order for transactions. We design two approaches, the first where the commit order for transactions is agreed upon prior to executing them, and the second where transactions are executed without prior knowledge of the commit order while the ordering happens in parallel. We leverage serializable snapshot isolation (SSI) to guarantee that the replicas across nodes remain consistent and respect the ordering determined by consensus, and devise a new variant of SSI based on block height for the latter approach. We implement our system on PostgreSQL and present detailed performance experiments analyzing both approaches.

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