Example: Data Linking via Smart Contracts

Step-by-Step Implementation

Smart Contract Definition

Define the smart contract that will store hashes of the data.

pragma solidity ^0.8.0;

contract DataLinker {
    struct DataReference {
        string dataHash;
        string description;
        uint timestamp;
    }

    mapping(uint => DataReference) public dataReferences;
    uint public dataCount;

    event DataLinked(uint indexed dataId, string dataHash, string description, uint timestamp);

    function linkData(string memory _dataHash, string memory _description) public {
        dataCount++;
        dataReferences[dataCount] = DataReference(_dataHash, _description, block.timestamp);
        emit DataLinked(dataCount, _dataHash, _description, block.timestamp);
    }

    function getData(uint _dataId) public view returns (string memory, string memory, uint) {
        DataReference memory dataRef = dataReferences[_dataId];
        return (dataRef.dataHash, dataRef.description, dataRef.timestamp);
    }
}

Data Storage Off-Chain

Store the actual data on a decentralized storage network such as IPFS (InterPlanetary File System). Upload the data to IPFS and retrieve the hash.

ipfs add path/to/datafile

This command will return a hash, for example: QmXoYP4F2zYF3....

Link Data to Smart Contract

Use the hash obtained from IPFS to link the data to the smart contract.

const Web3 = require('web3');
const web3 = new Web3('https://your-evire-node');

const contractABI = [ /* ABI from the compiled smart contract */ ];
const contractAddress = '0xYourContractAddress';
const dataLinker = new web3.eth.Contract(contractABI, contractAddress);

const dataHash = 'QmXoYP4F2zYF3...';
const description = 'Example data description';

dataLinker.methods.linkData(dataHash, description).send({ from: '0xYourAddress' })
    .on('receipt', function(receipt){
        console.log('Data linked:', receipt);
    });

Retrieve Linked Data

Fetch the linked data from the smart contract using its ID.

dataLinker.methods.getData(1).call()
    .then(function(result) {
        console.log('Data Hash:', result[0]);
        console.log('Description:', result[1]);
        console.log('Timestamp:', result[2]);
    });

Benefits

Immutable References, with hashes stored on-chain serving as immutable references to the off-chain data, ensuring data integrity and security.
Data Integrity, by using cryptographic hashes, any alteration in the actual data will result in a different hash, making it easy to detect tampering.
Efficiency, by storing large data off-chain, reducing the storage burden on the blockchain, and improving performance and scalability.
Flexibility, allowing for the integration of various decentralized storage solutions, adapting to different application needs.

Considerations

Data Privacy, by ensuring that sensitive data is adequately encrypted before uploading it to decentralized storage.
Redundancy, through the utilization of multiple storage nodes and redundancy protocols to avoid single points of failure and enhance data availability.
Cost, by being mindful of the transaction costs associated with storing and retrieving data references on the blockchain.

Implementing data linking via smart contracts on the Evire blockchain provides a robust solution for maintaining the integrity and accessibility of off-chain data. By leveraging decentralized storage networks, this approach combines the strengths of blockchain immutability with the scalability of off-chain data management,

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Last updated 1 year ago

pragma solidity ^0.8.0; contract DataLinker { struct DataReference { string dataHash; string description; uint timestamp; } mapping(uint => DataReference) public dataReferences; uint public dataCount; event DataLinked(uint indexed dataId, string dataHash, string description, uint timestamp); function linkData(string memory _dataHash, string memory _description) public { dataCount++; dataReferences[dataCount] = DataReference(_dataHash, _description, block.timestamp); emit DataLinked(dataCount, _dataHash, _description, block.timestamp); } function getData(uint _dataId) public view returns (string memory, string memory, uint) { DataReference memory dataRef = dataReferences[_dataId]; return (dataRef.dataHash, dataRef.description, dataRef.timestamp); } }

const Web3 = require('web3'); const web3 = new Web3('https://your-evire-node'); const contractABI = [ /* ABI from the compiled smart contract */ ]; const contractAddress = '0xYourContractAddress'; const dataLinker = new web3.eth.Contract(contractABI, contractAddress); const dataHash = 'QmXoYP4F2zYF3...'; const description = 'Example data description'; dataLinker.methods.linkData(dataHash, description).send({ from: '0xYourAddress' }) .on('receipt', function(receipt){ console.log('Data linked:', receipt); });

dataLinker.methods.getData(1).call() .then(function(result) { console.log('Data Hash:', result[0]); console.log('Description:', result[1]); console.log('Timestamp:', result[2]); });