We propose a blockchain-based non-repudiation scheme to build trust between the data owners and data buyers for IoT data trading. The proposed scheme uses smart contract to achieve automatic payment, which does not require a third-party. To enable non-repudiation, the proposed scheme records data sending and the corresponding receipt proof on the blockchain. When disputes happen, the smart contract is triggered to achieve automatic arbitration.
The system model is shown as the following figure and the smart contract code can be found in non-repudiation.sol file.
We prototyped and evaluated the proposed scheme using the Ethereum Kovan test blockchain. We wrote a Java program to interact with the Kovan test blockchain network and implements the off-chain part. In order to deploy and call the smart contract, we use the web3j package, which is a lightweight and type-safe Java library for working with smart contracts on the Ethereum network.
You can run the CreateWallet.java to create your wallet.
You need to create three wallet for test, including arbitrator、data owner and data buyer.
Moreover, you need to obtain the test Ether token of the Kovan chain to be able to pay for the gas by deploying the contract.
In order to use our java code to deploy and call the smart contract, you need to modify the configuration file properties first, and then run the ContractDeploy.java to deploy the smart contract.
After deployment, you can get the contract address.
You can choose a file and run the ContractCall.java to run test the contract method.
In this code, this.messageBitLength means the size of S2, so you can change it from a small one to a large one to test the contract.
ContractGas.java can test the gas cost of each function of the contract.
OffchainComputationCost.java can test the off-chain cost.