Networking, consensus, and security of blockchain applications

区块链技术还远未成熟。我们的建议集中在三个需要进一步发展的关键领域：基于区块链的分布式账簿的网络性能优化、共识机制以及区块链中存储的数据的安全和隐私。我们将研究网络特性对系统性能的影响，特别是对数据块传播和确认时间、分叉概率和分类帐不一致时间的影响。我们将设计、开发和评估高级机制、协议和消息格式，以限制分叉等不一致的可能性，并减少带宽使用。拟议的更改将有助于提高分类账数据的一致性、处理速度和准确性，从而减少基于区块链的系统的攻击面。我们计划专注于混合共识方法，这些方法可以限制延迟并保证终局性，就像PBFT(实用拜占庭容错)这样的集中式共识算法一样，但也提供了在分布式、无许可环境中的简单性和易用性，就像比特币中使用的Nakamoto共识一样。我们将开发创新机制，以实现这两个有些冲突的要求之间的最佳权衡，使用具有灵活成员资格的分布式范例和轮流协商一致的领导人。最后，我们将研究使用区块链技术为安全和隐私至关重要的垂直行业开发尖端应用程序，特别是在物联网(IoT)和电子医疗系统中。物联网系统构成了挑战，因为大量计算和通信能力有限的设备无法维护全面的区块链。因此，区块链将用于物联网设备和物联网网关的相互认证，或者更有可能的是边缘或云服务器的相互认证，还将帮助数据聚合和后续验证。由于用户数量庞大，以及个人需要控制对其医疗数据的访问，医疗保健系统构成了巨大的挑战。我们设想，区块链技术将用于支持基本的安全功能，但由于其规模，不会收集或存储实际数据。相反，区块链将持有用户身份验证信息、数据所有者的访问授权以及(可能)这些授权的后续撤销，(最重要的)它将记录必须根据访问时有效的授权执行的每一次数据访问的信息。我们还将研究分片技术，允许用户在本地存储中仅保留全局区块链的一部分，以便于访问，同时保持与全球区块链的同步。

Blockchain technology is still far from maturity. Our proposal focuses on three crucial areas in need of further development: network performance optimization for distributed blockchain-based ledgers, consensus mechanisms, and security and privacy of data stored in the blockchain. We will investigate the impact of network characteristics on system performance, in particular on block propagation and confirmation time, probability of forking, and ledger inconsistency time. We will devise, develop, and evaluate advanced mechanisms, protocols, and message formats that will restrict the potential for inconsistencies such as forking and reduce bandwidth usage. The proposed changes will contribute to increased consistency, processing rate, and accuracy of ledger data and, thus, reduce the attack surface of blockchain-based systems. We plan to focus on hybrid consensus approaches that limit latency and guarantee finality, as is the case with centralized consensus algorithms such as PBFT (Practical Byzantine Fault Tolerance) but also offer the simplicity and ease of use in a distributed, permissionless environment, as is the case with the Nakamoto consensus used in Bitcoin. We will develop innovative mechanisms to achieve the best tradeoff between the two somewhat conflicting requirements, using the distributed paradigm with flexible membership and a rotating consensus leader. Finally, we will investigate the use of blockchain technology to develop cutting edge applications for vertical industries where security and privacy is of paramount importance, in particular in Internet of Things (IoT) and e-healthcare systems. IoT systems pose a challenge due to the large number of devices with restricted computational and communication capabilities that cannot maintain a full blown blockchain. Thus blockchain will be used for mutual authentication of IoT devices and IoT gateways or, more likely, edge or cloud servers, and also to assist in data aggregation and subsequent verification.  Healthcare systems pose a big challenge on account of the large number of users and the need for individuals to control access to their healthcare data. We envisage that blockchain technology will be used to support basic security functions but not collect or store actual data due to its size. Instead, blockchain will hold user authentication information, access authorizations by data owners and (possibly) subsequent revocations of those authorizations, and (most importantly) it will record information about each and every data access that must be executed in accordance with the authorization valid at the moment of access. We will also look into sharding techniques that allow users to maintain only a portion of the global blockchain in their local storage for easy access whilst maintaining synchronism with the global blockchain.