Towards Scaling Blockchain Systems via Sharding

Existing blockchain systems scale poorly because of their distributed consensus protocols. Current attempts at improving blockchain scalability are limited to cryptocurrency. Scaling blockchain systems under general workloads (i.e., non-cryptocurrency applications) remains an open question. In this work, we take a principled approach to apply sharding, which is a well-studied and proven technique to scale out databases, to blockchain systems in order to improve their transaction throughput at scale. This is challenging, however, due to the fundamental difference in failure models between databases and blockchain. To achieve our goal, we first enhance the performance of Byzantine consensus protocols, by doing so we improve individual shards' throughput. Next, we design an efficient shard formation protocol that leverages a trusted random beacon to securely assign nodes into shards. We rely on trusted hardware, namely Intel SGX, to achieve high performance for both consensus and shard formation protocol. Third, we design a general distributed transaction protocol that ensures safety and liveness even when transaction coordinators are malicious. Finally, we conduct an extensive evaluation of our design both on a local cluster and on Google Cloud Platform. The results show that our consensus and shard formation protocols outperform state-of-the-art solutions at scale. More importantly, our sharded blockchain reaches a high throughput that can handle Visa-level workloads, and is the largest ever reported in a realistic environment.Comment: This is an updated version of the Chain of Trust: Can Trusted Hardware Help Scaling Blockchains? paper. This version is to be appeared in SIGMOD 201

Cryptographic approaches for confidential computations in blockchain.

Blockchain technologies have been widely re- searched in the last decade, mainly because of the revolution they propose for different use cases. Moving away from centralized solutions that abuse their capabilities, blockchain looks like a great solution for integrity, transparency, and decentral- ization. However, there are still some problems to be solved, lack of privacy being one of the main ones. In this paper, we focus on a subset of the privacy area, which is confidentiality. Although users are increasingly aware of the importance of confidentiality, blockchain poses a barrier to the confidential treatment of data. We initiate the study of cryptographic confidential computing tools and focus on how these technologies can endow the blockchain with better capabilities, i.e., enable rich and versatile applications while pro- tecting users’ data. We identify Zero Knowledge Proofs, Fully Homomorphic Encryption, and Se- cure Multiparty Computation as good candidates to achieve this.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The Ritva Blockchain: Enabling Confidential Transactions at Scale

The distributed ledger technology has been widely hailed as the break-through technology. It has realised a great number of application scenarios, and improved workflow of many domains. Nonetheless, there remain a few major concerns in adopting and deploying the distributed ledger technology at scale. In this white paper, we tackle two of them, namely the throughput scalability and confidentiality protection for transactions. We learn from the existing body of research, and build a scale-out blockchain platform that champions privacy called RVChain. RVChain takes advantage of trusted execution environment to offer confidentiality protection for transactions, and scales the throughput of the network in proportion with the number of network participants by supporting parallel shadow chains.Comment: The paper has been updated to address the editorial comments. arXiv admin note: substantial text overlap with arXiv:1905.06460, arXiv:1811.12628 by other author

Performance Improvement by Using Pipelined Execution on Hyperledger Fabric

The rapid growth of proofs of concept blockchain applications leads to increasing interest in understanding and improving blockchain performance at scale. However, the lower performance of blockchain restricts its application in some fields. Our work is focused on evaluating and improving the performance of Hyperledger Fabric, which is the most popular blockchain platform for enterprises. In previous works, the major bottleneck incurred in the validation & commit (V&C) module was studied, and many performance issues arising with it were alleviated to some context. The throughput is still only 900 transactions/second in our experiment. In this paper, a comprehensive latency evaluation for the V&C module was first performed. Then, according to the analysis of the evaluation results, a pipelined execution technology was proposed to process multiple blocks in parallel. Additionally, some pipeline acceleration schemes were also proposed to further improve the performance. Our experiments indicated performance improvements of 4.38× for LevelDB and at least 2× for CouchDB. Notably, our optimizations are transparent to blockchain applications and are suitable for integrating into a future version of Fabric

Anchoring the value of cryptocurrency

A decade long thrive of cryptocurrency has shown its potential as a source of alternative-finance and the security and the robustness of the underpinning blockchain technology. However, most cryptocurrencies fail to show inimitability and their meanings in the real world. As a result, they usually start off as favourites but quickly become the outcasts of the digital asset market. The blockchain society attempts to anchor the value of cryptocurrency with real values by employing smart contracts and link it with computation resources and the digital-productivity that have value and demands in the real world. But their attempts have some undesirable effects due to a limited number of practical applications. This limitation is caused by the dilemma between high performance and decentralisation (universal joinability). The emerging of blockchain sharding models, however, has offered a possible solution to address this dilemma. In this paper, we explore a financial model for blockchain sharding that will build an active link between the value of cryptocurrency and computation resources as well as the market and labour behaviours. Our model can adjust the price of resources and the compensation for maintaining a system based on those behaviours. We anchor the value of cryptocurrency by the amount of computation resources participated in and give the cryptocurrency a meaning as the exchange between computation resources globally. Finally, we present a working example which, through financial regularities, regulates the behaviour of anonymous participants, also incents/discourages participation dynamically