Porthos: Macroprogramming Blockchain Systems

Abstract

The rise of blockchain technology has paved the way for an increasing number of blockchain systems, each having different characteristics. The need for distributed applications that span across multiple blockchain systems is increasing. However, it is currently not possible to write a single-description smart contract which can be compiled to span across multiple blockchain systems. In this paper we present PORTHOS, a macroprogramming framework and domain specific language for writing commitment-based smart contracts that span multiple blockchain systems. The language allows programmers to write smart contracts at a higher level of abstraction by composing together contract blocks, without the need to specify how logic should be split across different blockchain instances. A runtime framework, including both on-chain and off-chain functionality, harmonises the features of different blockchain systems as well as enables communication across the smart contracts. A proof of concept, built on the Ethereum and Hyperledger Fabric blockchain systems and extendible to other systems, illustrates the technique and framework. We also show how the PORTHOS language is expressive enough to define a variety of applications.