ECCB: Boosting Block Propagation of Blockchain with Erasure-Coded Compact Block

Blockchain, the cornerstone for building the next generation of trustworthy web, suffers from poor scalability. Accelerating block propagation among blockchain nodes through block compression is an effective approach to improving scalability. However, existing block compression techniques, due to either low compression ratios or high recommunication ratios, induce either high transmission latency (proportional to block size, for a given Internet bandwidth) or multi-round Internet delay (dominated by geographical separation), causing significant network latency. To address both issues simultaneously, we propose a novel block propagation protocol, Erasure-Coded Compact Block (ECCB). It is motivated by and designed to exploit the significant transactional redundancy empirically observed in propagating blocks from six Ethereum nodes deployed across three continents. This redundancy refers to two key observations we made. First, most transactions in a propagating block (called hitting transactions) already exist in nodes' local transaction pools. Second, almost all of the remaining non-hitting transactions in the block (called missing transactions) are overlapping between neighboring nodes. Thus, rather than propagating all transactions within a propagating block, ECCB only propagates the much smaller-sized parity data that is erasure-code generated from these transactions. When receiving an ECCB block, a node combines the parity data with the dominant hitting transactions already existing in the local transaction pool to reconstruct the missing transactions, thus significantly compressing the propagating block. Meanwhile, recommunication is avoided by transmitting slightly more parity data than the predicted total size of all missing transactions, leveraging the high degree of overlap in missing transactions between neighboring nodes. Results from both simulation and prototyping experiments demonstrate the high efficacy of ECCB.