A Gateway-based Interoperability Solution for Permissioned Blockchains

During the last years, interoperability has become one of the main challenges within blockchain research as blockchains increasingly require integration between each other. Indeed, blockchains work by design in silos of information as interoperability is not a native feature. The main efforts in the field target permissionless blockchains, such as Bitcoin and Ethereum. However, interoperability in permissioned blockchains remains as an almost untouched area of work as they introduce additional requirements focusing on privacy and identity. Although there are some interoperability solutions for permissioned blockchains, they are either high-level design proposals not providing concrete implementations or focus on interoperability issues between business applications and blockchain platforms. In this paper we propose a gateway-based platform-to-platform interoperability solution for permissioned blockchains, which comprises a detailed solution design and a reference implementation. The proposal was assessed through the development of a social security case scenario, based on the reference implementation and using two blockchain platforms: Hyperledger Fabric and Corda.

I. Introduction

Blockchain is a distributed ledger technology to manage data in a decentralized way. Bitcoin, its first application, has the purpose of providing a software infrastructure for decentralized payments on untrusted environments [1]. Bitcoin leaded the first generation of blockchains, which provides user anonymity, data immutability and transparency over a decentralized network of untrusted participants. Trust is achieved by following rules defined by consensus protocols that guarantee and define how transactions are reliably registered into the ledger, avoiding the misbehaviour of malicious participants. A second generation of blockchains, leaded by Ethereum [2], added support for Turing complete scripting capabilities and state management, that enable and provide support for new use cases besides cryptocurrency exchange and transfer (e.g. art sale). More recently, organizations started building consortiums and using blockchain technology to improve their business processes, leading to enterprise blockchains [3]. These blockchains have additional requirements (e.g. data privacy and user identification) which were not supported by the original design features provided by Bitcoin and Ethereum. In fact, they need to be closed and permissioned as opposed to the later, which are open and unrestricted, allowing users to have full access to the ledger, participate on the consensus protocol and record transactions. As a consequence, a new generation of blockchains emerged to fulfill these requirements (e.g. Hyperledger Fabric [4] and Corda [5]). These new permissioned blockchains require users to be identified and granted permissions in order to have access to the ledger or participate in the consensus protocol as opposed to previous permissionless blockchains.