Consensus Protocols in Blockchains: Performance and Scalability

PhD Qualifying Examination


Title: "Consensus Protocols in Blockchains: Performance and Scalability"

by

Mr. Zonghao FENG


Abstract:

A blockchain system, exemplified by cryptocurrencies such as Bitcoin and 
Ethereum, consists of a distributed collection of immutable data blocks 
linked to one another. Due to the distributed nature of the system, the 
users observe a consensus protocol to verify data authenticity and 
interact with others without a trusted third party. In this survey, we 
study the existing consensus protocols in blockchains, and focus on their 
performance and scalability issues. Specifically, we examine four 
categories of consensus protocols - Proof-of-Work, Proof-of-X, block 
direct acyclic graph (DAG), and sharding. Proof-of-Work requires heavy 
computation or intensive memory access. Conversely, most Proof-of-X 
protocols use light workloads to reduce energy waste and avoid 
centralization. Since they both operate on the original blockchain 
structure, these systems suffer from low transaction throughput and high 
latency. In comparison, block DAG and sharding reorganize the underlying 
blockchain structure to improve the performance and scalability, but their 
applicability to real systems is yet to be seen. Additionally, we discuss 
the use of modern hardware, including CPUs, GPUs, and special-purpose 
devices, as accelerators in blockchain systems. We conclude that 
performance and scalability remain a great challenge in current blockchain 
technology and that further research is needed to address the challenge.


Date:			Monday, 28 January 2019

Time:                  	2:00pm - 4:00pm

Venue:                  Room 3494
                         Lifts 25/26

Committee Members:	Dr. Qiong Luo (Supervisor)
 			Prof. Lei Chen (Chairperson)
 			Dr. Qifeng Chen
 			Dr. Ke Yi


**** ALL are Welcome ****