Trustworthy Cloud Service Level Agreement Enforcement with Blockchain based Smart Contract

Cloud Service Level Agreement (SLA) is challengeable

due to lacking a trustworthy platform. This paper presents

a witness model to credibly enforce the cloud service level

agreement. Through introducing the witness role and using

the blockchain based smart contract, we solve the trust issues

about who can detect the service violation, how the violation is

confirmed and the compensation is guaranteed. In this model,

a verifiable consensus sortition algorithm proposed by us is

firstly leveraged to select independent witnesses to form a witness

committee. They are responsible for a specific service level agreement

and get paid by monitoring and detecting service violation.

Through carefully designing the witness’ payoff function in the

agreement, we further leverage game theory to analyze and

prove that it is not the witness itself is trustworthy. Instead,

the witness has to tell the truth because of its greedy nature,

which is the desire to maximize its own revenue. As long as

the service violation is confirmed by the witness committee, the

compensation is automatically transferred to the customer by

the smart contract. Finally, we implement a proof-of-concept

prototype with the smart contract of Ethereum blockchain. It

demonstrates the feasibility of our model.