City Research Online

Proof-of-Prestige: A Useful Work Reward System for Unverifiable Tasks

Krol, M. ORCID: 0000-0002-3437-8621, Sonnino, A., Al-Bassam, M. , Tasiopoulos, A. G., Riviere, E. & Psaras, I. (2021). Proof-of-Prestige: A Useful Work Reward System for Unverifiable Tasks. ACM Transactions on Internet Technology (TOIT), 21(2), pp. 1-27. doi: 10.1145/3419483


As cryptographic tokens and altcoins are increasingly being built to serve as utility tokens, the notion of useful work consensus protocols is becoming ever more important. With useful work consensus protocols, users get rewards after they have carried out some specific tasks useful for the network. While in some cases the proof of some utility or service can be provided, the majority of tasks are impossible to verify reliably. To deal with such cases, we design “Proof-of-Prestige” (PoP)—a reward system that can run directly on Proof-of-Stake (PoS) blockchains or as a smart contract on top of Proof-of-Work (PoW) blockchains. PoP introduces “prestige,” which is a volatile resource that, in contrast to coins, regenerates over time. Prestige can be gained by performing useful work, spent when benefiting from services, and directly translates to users minting power. Our scheme allows us to reliably reward decentralized workers while keeping the system free for the end-users. PoP is resistant against Sybil and collusion attacks and can be used with a vast range of unverifiable tasks. We build a simulator to assess the cryptoeconomic behavior of the system and deploy a full prototype of a content dissemination platform rewarding its participants. We implement the blockchain component on both Ethereum (PoW) and Cosmos (PoS), provide a mobile application, and connect it with our scheme with a negligible memory footprint. Finally, we adapt a fair exchange protocol allowing us to atomically exchange files for rewards also in scenarios where not all the parties have Internet connectivity. Our evaluation shows that even for large Ethereum traces, PoP introduces sub-millisecond computational overhead for miners in Cosmos and less than 0.013$ smart contract invocation cost for users in Ethereum.

Publication Type: Article
Additional Information: This is the authors’ accepted manuscript. The final version of this work is published by ACM in ACM Transactions on Internet Technology, available at DOI: This work is made available online in accordance with the publisher’s policies. Please refer to any applicable terms of use of the publisher.
Publisher Keywords: Blockchain, Security and privacy, Network security
Subjects: H Social Sciences > HB Economic Theory
Q Science > QA Mathematics > QA75 Electronic computers. Computer science
Departments: School of Science & Technology > Computer Science
School of Science & Technology > Computer Science > Software Reliability
SWORD Depositor:
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