Resolving blockchain trilemmas

Rana, Ranvir

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https://hdl.handle.net/2142/117780 Copy

Description

Title

Resolving blockchain trilemmas

Author(s)

Rana, Ranvir

Issue Date

2022-11-29

Director of Research (if dissertation) or Advisor (if thesis)

Viswanath, Pramod

Doctoral Committee Chair(s)

Viswanath, Pramod

Committee Member(s)

• Hajek, Bruce
• Srikant, Rayadurgam
• Miller, Andrew
• Ren, Ling

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Blockchain, Bootstrapping, Sharding, Resource Allocation, Distributed Systems

Abstract

Three ideal properties characterize a blockchain: decentralization, security, and scalability. Existing blockchain designs satisfy at most two of the three properties; as examples, consider: Bitcoin is decentralized and secure, but not scalable; EOS, TRON, and several proof-of-stake blockchains are secure and scalable, but not decentralized; Conflux and IOTA are decentralized and scalable, but not secure. Unsuccessful attempts to build scalable, decentralized, and secure blockchains, constituting all three properties, have led to a folk theorem known as the blockchain protocol trilemma, which states that a blockchain can achieve only two of the three ideal properties. In this dissertation, we disprove this trilemma by proposing Trifecta, a blockchain architecture that achieves all three properties by being: (1) decentralized, with a limited amount of compute, storage, and communication resources per node; (2) secure against fully adaptive adversaries with hashing power up to the honest power of the entire network; and (3) throughput scaling near linearly with the number of network nodes. We implement Trifecta as a full-stack blockchain in Rust and demonstrate a total throughput of 250K transactions per second. A key component of the Trifecta architecture is Free2Shard, a distributed resource allocation algorithm that ensures that each shard has sufficient honest mining power under an adaptive adversary. We show the performance of Free2Shard to be near information-theoretically optimal by connecting to the classical work of Blackwell approachability in dynamic game theory. In a separate line of work, a blockchain economics trilemma is posited in the literature: at most two of the following three economic properties are satisfied by any blockchain design – self-sufficient, rent-free, and resource-efficient. We argue that Trifecta with Free2Shard optimizes the rent and resource cost per transaction and propose Advocate to minimize the legal costs associated with bootstrapping PoW blockchains. Advocate is a bootstrapping gadget that achieves optimal chain quality even under adversarial mining majority and can be expended to work on any parallel chain type blockchains. We demonstrate the robustness of Advocate under a 90% adversarial majority via a full-stack implementation.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Ranvir Rana

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