Toward a Fast and Secure Blockchain Framework for Smart Contracts

随着加密货币的成功，区块链最近发生了演变 转变为安全、分散、一致的技术平台 互联网规模的交易分类账。智能合同部署是 许多区块链系统的重要功能。用户可以开发智能合同 对任意复杂的交易规则进行编码并部署这些合同 区块链系统。然后，合同(即交易规则) 由系统的所有参与者忠实地执行和执行，消除 未来编码交易的任何潜在交易对手风险。 采用智能合同技术的一个挑战是安全性 风险。因为智能合同实际上是直接操纵 数字资产，确保这些合同的正确性是非常关键的。 不幸的是，人类程序员经常犯错误。这个 SMART中编程错误和安全漏洞的后果 合同特别严重，往往导致数千万美元 损失。采用的另一个挑战是性能问题。为了确保 交易分类账的一致性、共识协议 区块链系统必须以缓慢的区块生成运行，以避免 并发阻塞(即，分叉)，被认为对共识有害 安全。因此，这些系统的事务吞吐量非常有限 聪明的合同。用户通常需要等待很长一段时间才能确认 一笔交易。 为了应对安全挑战，我们建议设计一套新的工具来 保护智能合同，将静态分析与运行时相结合 乐器。一种观察结果是，事务执行不是 区块链平台的瓶颈。相反，瓶颈首先在 共识协议，然后在区块链存储层。因此， 运行时检测的开销，这通常对其他设备来说过于昂贵 事实上，对于智能合同来说，域名可以忽略不计。在表演中表现出色 挑战，我们建议设计一种新的共识协议，该协议可以重组 块到有向无环图中，以安全地合并并发块。这个 协议内在地编码了两种策略，一种乐观的策略 业绩和保守的战略，确保协商一致取得进展 挫败活跃性攻击。我们还建议重新考虑存储的设计 层和事务传播来构建高性能的端到端 区块链平台。 如果拟议的研究取得成功，拟议的技术将使 智能合约的发展明显更加安全。这些技术 还将允许区块链平台以更高的速度处理智能合同 吞吐量和更快的速度。拟议研究的最终目标是 寻找全面的解决方案，充分发挥智能合同的潜力 技术。

Following the success of the cryptocurrencies, blockchain has recently evolved into a technology platform that powers secure, decentralized, and consistent transaction ledgers at Internet-scale. Smart contract deployment is the most important feature of many blockchain systems. Users can develop smart contracts to encode arbitrarily complicated transaction rules and deploy these contracts to a blockchain system. The contracts (i.e., transaction rules) are then faithfully executed and enforced by all participants of the system, eliminating any potential counter-party risk of the encoded transactions in future. One challenge for the adoption of smart contract techniques is the security risk. Because smart contracts are in fact programs that directly manipulate digital assets, ensuring the correctness of these contracts is very critical. Unfortunately, human programmers often make mistakes and errors. The consequence of programming errors and security vulnerabilities in smart contracts is particularly severe, often leading to tens of millions of dollar losses. Another challenge for the adoption is the performance issue. To ensure the consistency of the transaction ledger, the consensus protocols in blockchain systems have to operate with slow block generation to avoid concurrent blocks (i.e., forks), which are considered harmful for the consensus safety. Therefore these systems have very limited transaction throughputs for smart contracts. Users often have to wait for a long period of time to confirm a transaction. To tackle the security challenge, we propose to design a new set of tools for securing smart contracts, combining the static analysis with runtime instrumentations. One observation is that the transaction execution is not the bottleneck in blockchain platforms. The bottleneck is instead first at the consensus protocol and then at the blockchain storage layer. Therefore the overhead of runtime instrumentation, which is often too expensive for other domains, is in fact negligible for smart contracts. To tackle the performance challenge, we propose to design a novel consensus protocol that reorganizes blocks into direct acyclic graph to safely incorporate concurrent blocks. The protocol inherently encodes two strategies, an optimistic strategy for high performance and a conservative strategy that ensure the consensus progress to thwart liveness attacks. We also propose to revisit the design of the storage layer and the transaction propagation to build a high performance end-to-end blockchain platform. If the proposed research becomes successful, the proposed techniques would make the development of smart contracts significantly more secure. The techniques would also allow blockchain platforms to process smart contracts at a higher throughput and a faster speed. The ultimate goal of the proposed research is to find comprehensive solutions to unleash the full potential of smart contract technologies.