Towards Efficient and Decentralized Spatial Crowdsourcing

PhD Thesis Proposal Defence


Title: "Towards Efficient and Decentralized Spatial Crowdsourcing"

by

Mr. Mingzhe LI


Abstract:

With the proliferation of mobile devices, spatial crowdsourcing has emerged as 
a transformative system, where requesters outsource their spatio-temporal tasks 
to workers who are willing to perform the tasks at specified locations. 
However, existing spatial crowdsourcing usually suffers from the problem of 
centralization and limited efficiency. To address the above issues, we make the 
following contributions.

First, we propose PriTA, a distributed spatial crowdsourcing framework which 
protects PRIvacy and achieves efficient Task Assignment. It protects 
workers’/tasks’ location privacy through homomorphic encryption. Novel 
wait-and-decide and proportional-backoff mechanisms are proposed to increase 
the number of assigned tasks.

Second, a decentralized, secure, transparent and fair platform is essential for 
spatial crowdsourcing. The emergence of blockchain has made it possible. 
Requesters and workers can invoke smart contracts (functions executing various 
logic) in blockchain to handle task assignment and reward settlement without 
worrying about manipulation of assignment and settlement results. However, 
existing blockchain-based crowdsourcing systems generally suffer from the issue 
of lacking efficient task assignment schemes and the risk of losing 
requesters’/worker’ deposit. Thereby, we design SC-EOS, a blockchain-based 
spatial crowdsourcing framework. It frees users from deposits by linking every 
action for each user, and provides efficient and user-customizable task 
assignment via judicious smart contract modifications and design.

Finally, a critical efficiency issue when applying blockchain to crowdsourcing 
is its poor scalability. Sharding is proposed to improve blockchain 
scalability, increasing throughput by partitioning nodes into multiple smaller 
groups. However, when tackling smart contracts, existing blockchain sharding 
protocols do not scale well. We therefore present Jenga, a novel sharding-based 
approach for efficient smart contract processing. It requires all shards share 
the logic for all contracts, so that smart contracts can be executed within one 
round. Moreover, different shards store distinct states (state shards), several 
"orthogonal" execution channels are established based on the state shards to 
reduce cross-shard communication.


Date:			Wednesday, 13 April 2022

Time:                  	3:00pm - 5:00pm

Zoom Meeting:
https://hkust.zoom.us/j/95006228325?pwd=OEtEQmtvbTVvNDdhTE12NWNrdXNZQT09

Committee Members:	Dr. Wei Wang (Supervisor)
 			Prof. Jin Zhang (Supervisor, SUSTech)
  			Prof. Lei Chen (Chairperson)
 			Prof. Gary Chan
 			Prof. Bo Li


**** ALL are Welcome ****