MoL-2017-29: Leaning on Impossible-to-Parallelise Work for Immutability Guarantees in the Blockchain

MoL-2017-29: Landerreche, Esteban (2017) Leaning on Impossible-to-Parallelise Work for Immutability Guarantees in the Blockchain. [Report]

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Blockchains are structures that allow to establish trust by relying on cryptographic primitives to ensure that the information encoded in them cannot be changed. Bitcoin is the first example of a blockchain and an important amount of the research is concerned with replicating its advantages in other settings. Another avenue of research focuses on improving on the flaws of Bitcoin, like how it incentivises parallelisation and is vulnerable to quantum attacks. An important limitation of Bitcoin is that its immutability guarantees can only be maintained in a large network at a large cost, making it unusable for many applications. In this thesis, we present a blockchain protocol that avoids these issues by ensuring immutability through proofs of work based on sequential computation. By separating the proofs of work from the consensus mechanism, we avoid the incentives for parallelisation found in Bitcoin while maintaining similar guarantees that the information contained within cannot be changed. First, we present the security guarantees that serial proofs of work contribute to the blockchain structure. We then construct a protocol in a modular way through the universal composability framework in an idealised setting and prove that it is secure. Next, we get rid of many of the idealising assumptions and show that our model is still secure. Finally, we introduce a new setting for the use of blockchains, with peers maintaining personal blockchains that form a web of trust. We believe that the models presented in this work will be able to replicate the immutability guarantees of Bitcoin in a permissioned setting while avoiding some of the setbacks of that model.

Item Type: Report
Report Nr: MoL-2017-29
Series Name: Master of Logic Thesis (MoL) Series
Year: 2017
Subjects: Computation
Depositing User: Dr Marco Vervoort
Date Deposited: 19 Oct 2017 15:53
Last Modified: 19 Oct 2017 15:55

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