University of Twente Student Theses


Guaranteed-TX : The exploration of a guaranteed cross-shard transaction execution protocol for Ethereum 2.0.

Wels, S.J. (2019) Guaranteed-TX : The exploration of a guaranteed cross-shard transaction execution protocol for Ethereum 2.0.

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Abstract:A major bottleneck of the state-of-the-art distributed ledgers is the limited transaction throughput. Existing ledgers lack scalability and are unable to process transactions at the speed of centralised systems. One technique used by Ethereum 2.0 to overcome these performance and scalability limitations is sharding. With sharding, the computational work is partitioned among multiple, smaller groups of validators referred to as shards. These shards operate in parallel to increase the overall transaction throughput while minimising the communication, computation and storage requirements per node. However, the interoperability between shards is yet very limited. It can take several minutes before a shard is allowed to process a cross-shard transaction while there is no guarantee that a cross-shard transaction will be processed at all. Without interoperability improvements, sharding will only benefit smart contract applications that run within a single shard. In this study we propose Guaranteed-TX, a guaranteed cross-shard transaction execution protocol for Ethereum 2.0. Guaranteed-TX allows shards to process cross-shard transactions before being finalised in the block it was created - a property called optimistic execution - which significantly improves cross-shard transaction latencies. In addition, it provides economic guarantees that all cross-shard transaction will eventually be processed. In order to achieve both Guaranteed-TX introduces a messaging layer which records the created and processed cross-shard transactions and is shared with every shard. The messaging layer is used to finalise consistent blocks and punish validators in a shard committee for not processing cross-shard transactions. Consequently, cross-shard transactions are either processed or slowly drain the stake of the validators within the addressed shard. Although we prove correctness of Guaranteed-TX and show that it achieves theoretical satisfying performance, the protocol is build upon assumptions which yet have to been proven. The first phase of the Ethereum 2.0 transition is set for launch on January 3, 2020. However, it may take several years before cross-shard communication will be facilitated. In the meantime, many specifications may change and empirical evidence may confirm or invalidate our assumptions. Our findings show that a guaranteed cross-shard transaction protocol is feasible and the insights of this study should be used for further protocol developments.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:54 computer science
Programme:Computer Science MSc (60300)
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