RollupTheCrowd: Leveraging ZkRollups for a Scalable and Privacy-Preserving Reputation-based Crowdsourcing Platform

TL;DR

This work tackles the dual challenges of scalability and privacy in reputation-based crowdsourcing on blockchains by proposing RollupTheCrowd, a framework that leverages zkRollups (L2) to offload computation from the main chain and uses off-chain storage (IPFS) to reduce on-chain data. It introduces a privacy-preserving reputation model that evaluates workers through problem-solving and knowledge-acquisition tasks, with formal metrics and a dynamic update rule that reacts to behavior via $R_{new}$ calculated from $R_{old}$ and $T_R$. The architecture comprises a dual-layer main ledger, a decentralized identity registrar, IPFS-backed data storage, and interoperable data feeds through decentralized oracles, enabling secure, scalable, and auditable crowdsourcing workflows. Experimental proof-of-concept results show significant gas savings (up to ~20x) and favorable throughput/latency characteristics, supporting the practicality of real-world deployments and highlighting avenues for further enhancements in anonymity and privacy guarantees.

Abstract

Current blockchain-based reputation solutions for crowdsourcing fail to tackle the challenge of ensuring both efficiency and privacy without compromising the scalability of the blockchain. Developing an effective, transparent, and privacy-preserving reputation model necessitates on-chain implementation using smart contracts. However, managing task evaluation and reputation updates alongside crowdsourcing transactions on-chain substantially strains system scalability and performance. This paper introduces RollupTheCrowd, a novel blockchain-powered crowdsourcing framework that leverages zkRollups to enhance system scalability while protecting user privacy. Our framework includes an effective and privacy-preserving reputation model that gauges workers' trustworthiness by assessing their crowdsourcing interactions. To alleviate the load on our blockchain, we employ an off-chain storage scheme, optimizing RollupTheCrowd's performance. Utilizing smart contracts and zero-knowledge proofs, our Rollup layer achieves a significant 20x reduction in gas consumption. To prove the feasibility of the proposed framework, we developed a proof-of-concept implementation using cutting-edge tools. The experimental results presented in this paper demonstrate the effectiveness and scalability of RollupTheCrowd, validating its potential for real-world application scenarios.

Figures (6)

• Figure 1: High-Level System Architecture
• Figure 2: Dual Layers Workflow in RollupTheCrowd
• Figure 3: Decentralized Oracles in RollupTheCrowd
• Figure 4: The crowdsourcing workflow in RollupTheCrowd
• Figure 6: L1 Throughput and latency of CreateTask function under different Block Times = [1s,3s,5s]