sChain: An Efficient and Secure Solution for Improving Blockchain Storage

Emerging blockchain technology has become the cornerstone of many applications providing trusted data services. However, existing blockchain platforms cannot meet the growing demand for big data storage. Blockchain should duplicate both transactions and other user-defined data across nodes for integrity assurance. The rapid expansion of data on blockchain (on-chain data) increases the difficulty of deploying a full node, resulting in decreasing the degree of decentralization and adding the risk of broken data. To tackle these problems, we propose sChain, a novel framework for improving blockchain storage capacity, which does not revise blockchain implementation and can be applied to almost all the existing blockchain platforms. sChain outsources the user data to storage devices that are structurally external to the blockchain network. In theory, a user can outsource unlimited data to sChain. However, those off-chain data may suffer from corruption. To verify the data integrity, we propose a new provable data possession (PDP) scheme, which does not need a centralized entity to maintain any secret keys and therefore eliminates a single point of failure. What is more, we also design a prototype to accelerate the proposed PDP scheme through Intel SGX technology and parallel processing. Security analysis and evaluation results show that sChain can protect data security and effectively improve the blockchain storage capacity, respectively.