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Securely Scaling Blockchain Base Layers

Al Bassam, Mustafa; (2020) Securely Scaling Blockchain Base Layers. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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This thesis presents the design, implementation and evaluation of techniques to scale the base layers of decentralised blockchain networks---where transactions are directly posted on the chain. The key challenge is to scale the base layer without sacrificing properties such as decentralisation, security and public verifiability. It proposes Chainspace, a blockchain sharding system where nodes process and reach consensus on transactions in parallel, thereby scaling block production and increasing on-chain throughput. In order to make the actions of consensus-participating nodes efficiently verifiable despite the increase of on-chain data, a system of fraud and data availability proofs is proposed so that invalid blocks can be efficiently challenged and rejected without the need for all users to download all transactions, thereby scaling block verification. It then explores blockchain and application design paradigms that enable on-chain scalability on the outset. This is in contrast to sharding, which scales blockchains designed under the traditional state machine replication paradigm where consensus and transaction execution are coupled. LazyLedger, a blockchain design where the consensus layer separated from the execution layer is proposed, where the consensus is only responsible for checking the availability of the data in blocks via data availability proofs. Transactions are instead executed off-chain, eliminating the need for nodes to execute on-chain transactions in order to verify blocks. Finally, as an example of a blockchain use case that does not require an execution layer, Contour, a scalable design for software binary transparency is proposed on top of the existing Bitcoin blockchain, where all software binary records do not need to be posted on-chain.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Securely Scaling Blockchain Base Layers
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2020. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Computer Science
URI: https://discovery.ucl.ac.uk/id/eprint/10117245
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