CLOAK: Towards Practical Development and Deployment of Confidential Smart Contracts

In recent years, as blockchain adoption has been expanding across a wide range of domains, e.g., supply chain finance, digital asset, etc., the confidentiality of smart contracts is now a fundamental demand for practical applications. However, while new privacy protection techniques keep coming out, how existing ones can best fit development settings is little studied. State-of-the-art solutions suffer from limited architectural support in terms of programming interfaces, thus can hardly reach general developers. This paper proposes CLOAK, a pluggable and configurable framework for developing and deploying confidential smart contracts. The key capability of CLOAK is allowing developers to implement and deploy practical solutions to multi-party transaction (MPT) problems, i.e., transact with secret inputs and states owned by different parties, by simply specifying it. To this end, CLOAK allows users to specify privacy invariants in a declarative way, automatically generate runtime with verifiably enforced privacy and deploy it to the existing platforms with TEEBlockchain architecture to enable the MPT. In our evaluation on both examples and real-world applications, developers manage to deploy business services on blockchain in a concise manner by only developing CLOAK smart contracts whose size is less than 30% of the deployed ones and the gas cost of deployed MPTs reduces 19%.