SoK: Exploring Blockchains Interoperability

Distributed ledger technologies like blockchain have gained great attention in both academia and industry. Blockchain as a potentially disruptive technology can advance many different fields, e.g., cryptocurrencies, supply chains, and the industrial Internet of Things. The next-generation blockchain ecosystem is expected to consist of various homogeneous and heterogeneous distributed ledgers. These ledger systems will inevitably require a certain level of proper cooperation of multiple blockchains to enrich advanced functionalities and enhance interoperable capabilities for future applications. The interoperability among blockchains will definitely revolutionize current blockchain design principles, like the emergence of Internet. The development of cross-blockchain applications involves much complexity regarding the variety of underlying cross-blockchain communication. The way to effectively enable interoperability across multiple blockchains is thus essential and expecting to confront various unprecedented challenges. For instance, due to different transaction structures, ensuring the properties of ACID (Atomicity, Consistency, Isolation, Durability) in transactions processing and verification processes across diverse blockchain systems remains a challenging task in both academia and industry. This paper provides a systematic and comprehensive review of the current progress of blockchain interoperability. We explore both general principles and practical schemes to achieve interoperable blockchain systems. We then survey and compare the state-of-the-art solutions to deal with the interoperability of blockchains in detail. Finally, we discuss several critical challenges and some potential research directions to advance the research on exploring blockchain interoperability

Enabling Resilient and Efficient Communication for the XRP Ledger and Interledger

The blockchain technology is relatively new and still evolving. Its development was fostered by an enthusiastic community of developers, which sometimes forgot about the lessons from the past related to security, resilience and efficiency of communication which can impact network scalability, service quality and even service availability. These challenges can be addressed at network level but also at operating system level. At network level, the protocols and the architecture used play a major role, and overlays have interesting advantages like custom protocols and the possibility of arbitrary deployments. This thesis shows how overlay networks can be designed and deployed to benefit the security and performance in communication for consensus-validation based blockchains and blockchain inter-operativity, taking as concrete cases the XRP ledger and respectively the Interledger protocol. XRP Ledger is a consensus-validation based blockchain focused on payments which currently uses a flooding mechanism for peer to peer communication, with a negative impact on scalability. One of the proposed overlays is based on Named Data Networking, an Internet architecture using for propagation the data name instead of data location. The second proposed overlay is based on Spines, a solution offering improved latency on lossy paths, intrusion tolerance and resilience to routing attacks. The system component was also interesting to study, and the contribution of this thesis centers around methodologies to evaluate the system performance of a node and increase the security from the system level. The value added by the presented work can be synthesized as follows: i) investigate and propose a Named Data Networking-based overlay solution to improve the efficiency of intra-blockchain communication at network level, taking as a working case the XRP Ledger; ii) investigate and propose an overlay solution based on Spines, which improves the security and resilience of inter-blockchain communication at network level, taking as a working case the Interledger protocol; iii) investigate and propose a host-level solution for non-intrusive instrumentation and monitoring which helps improve the performance and security of inter-blockchain communication at the system level of machines running Distributed Ledger infrastructure applications treated as black-boxes, with Interledger Connectors as a concrete case

Enhancing Blockchain Performance and Security: Pushing the Limits of Decentralized Applications

Decentralized Applications (DApps) have seen exponential growth in the past decade leading to a new paradigm known as Web3. Web3 is the ecosystem formed by the execution of multiple DApps. Blockchains offer a platform for DApp executions. However, the performance and security of current blockchains is limited and impair the adoption of Web3. More specifically, for demanding DApp workloads, modern blockchains perform poorly or lose transactions. This thesis presents various contributions to enhance blockchain performance and security to widen the adoption of Web3. To enhance blockchain performance for DApp executions, we first present the Smart Redbelly Blockchain (SRBB). SRBB enhances DApp performance by reducing blockchain congestion. SRBB alone is not sufficient to service multiple demanding DApp workloads. Therefore, we introduce a DApp-oriented dynamic transparent sharding mechanism that concurrently execute DApps in separate shards. To boost the DApp performance of SRBB, we present a decoupled variant of SRBB known as Collachain. While blockchain performance is critical, existing blockchain designs are vulnerable to the formation of an oligarchy in the governance that can dictate the outcome of the protocol. Such an oligarchy can lead to the insecure execution of DApps, impairing the adoption of Web3. To mitigate the formation of an oligarchy in blockchain governance, we finally present a proportional governance protocol that proportionally elects a diverse set of governors to mitigate an oligarchy in the governance process