A Blockchain based Witness Model for Trustworthy Cloud Service Level Agreement Enforcement

Huan Zhou, Xue Ouyang, Zhijie Ren, Jinshu Su, Cees de Laat, Zhiming Zhao

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

28 Citations (Scopus)


Traditional cloud Service Level Agreement (SLA) suffers from lacking a trustworthy platform for automatic enforcement. The emerging blockchain technique brings in an immutable solution for tracking transactions among business partners. However, it is still very challenging to prove the credibility of possible violations in the SLA before recording them onto the blockchain. To tackle this challenge, we propose a witness model using game theory and the smart contract techniques. The proposed model extends the existing service model with a new role called 'witness' for detecting and reporting service violations. Witnesses gain revenue as an incentive for performing these duties, and the payoff function is carefully designed in a way that trustworthiness is guaranteed: in order to get the maximum profit, the witness has to always tell the truth. This is analyzed and proved through game theory using the Nash equilibrium principle. In addition, an unbiased sortition algorithm is proposed to ensure the randomness of the independent witnesses selection from the decentralized witness pool, to avoid possible unfairness or collusion. An auditing mechanism is also introduced in the paper to detect potential irrational or malicious witnesses. We have prototyped the system leveraging the smart contracts of Ethereum blockchain. Experimental results demonstrate the feasibility of the proposed model and indicate good performance in accordance with the design expectations.

Original languageEnglish
Title of host publicationIEEE INFOCOM 2019 - IEEE Conference on Computer Communications
Place of PublicationPiscataway, NJ
Number of pages9
ISBN (Electronic)978-1-7281-0515-4
ISBN (Print)978-1-7281-0516-1
Publication statusPublished - 2019
Event2019 IEEE Conference on Computer Communications, INFOCOM 2019 - Paris, France
Duration: 29 Apr 20192 May 2019


Conference2019 IEEE Conference on Computer Communications, INFOCOM 2019


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