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FDC-101: Flare Data Connector Examples

Documented working examples demonstrating the use of the Flare Data Connector (FDC). This code starts from a simplified version of the Flare Hardhat starter, and the purpose is purely educational. This first iteration focuses on how to bring external Web2 data sources onto the Flare blockchain.

What This Project Contains

  • Web2Json Attestations: Fetch and verify data from external APIs
  • Weather Insurance: Real-world insurance contracts using weather data
  • Proof of Reserves: Cryptographic proof systems for asset verification

Web2Json Attestation Example

Star Wars API Integration

  • Contract: StarWarsCharacterListV2 deployed at 0xE7f6ff7bD309621ae9e2339C829544E6C58bD8Ba
  • Network: Coston2 Testnet
  • Functionality: Fetches character data from Star Wars API and processes it on-chain
  • Verification: View on Block Explorer

Web2Json Flow Diagram

sequenceDiagram
    participant YourScript as Your Script (Web2Json.ts)
    participant Verifier as FDC Verifier Server<br/>(web2json-verifier-test.flare.rocks)
    participant FdcHub as FDC Hub Contract<br/>(on Flare blockchain)
    participant Validators as Flare Validators<br/>(decentralized network)
    participant StarWarsAPI as External API<br/>(swapi.info)
    participant DALayer as Data Availability Layer<br/>(API endpoint)
    participant FdcVerification as FDC Verification System<br/>(ContractRegistry)
    participant SmartContract as Your Smart Contract<br/>(StarWarsCharacterListV2)

    Note over YourScript,SmartContract: Phase 1: Request Preparation & Submission
    
    YourScript->>Verifier: 1. API URL + JQ filter + ABI signature
    Note right of YourScript: apiUrl: "https://swapi.info/api/people/3"<br/>postProcessJq: "{name: .name, height: .height, ...}"<br/>abiSignature: "{"components": [...], "type": "tuple"}"
    
    Verifier->>YourScript: 2. ABI-encoded request (hex string)
    Note left of Verifier: Converts human-readable request<br/>to binary format for blockchain
    
    YourScript->>FdcHub: 3. Submit attestation request (pay fee)
    Note right of YourScript: fdcHub.requestAttestation(abiEncodedRequest, {value: requestFee})
    
    Note over YourScript,SmartContract: Phase 2: Decentralized Data Acquisition & Verification
    
    FdcHub->>Validators: 4. Broadcast request (start voting round)
    Note left of FdcHub: Creates voting round<br/>Round ID: 1063464
    
    Validators->>StarWarsAPI: 5. Fetch raw data independently
    Note right of Validators: Each validator makes HTTP GET request<br/>to get raw JSON response
    
    StarWarsAPI->>Validators: 6. Return raw JSON data
    Note left of StarWarsAPI: {"name": "R2-D2", "height": "96",<br/>"mass": "32", "films": [...], ...}
    
    Validators->>Validators: 7. Apply JQ filter to raw data
    Note right of Validators: {name: .name, height: .height, mass: .mass,<br/>numberOfFilms: .films | length,<br/>uid: (.url | split("/") | .[-1] | tonumber)}
    
    Validators->>DALayer: 8. Submit attestations with processed data
    Note right of Validators: Each validator submits their<br/>processed result for voting
    
    DALayer->>DALayer: 9. Generate Merkle proof from attestations
    Note right of DALayer: Creates cryptographic proof<br/>when supermajority agrees
    
    Note over YourScript,SmartContract: Phase 3: Proof Retrieval & Smart Contract Usage
    
    YourScript->>DALayer: 10. Request proof by round ID
    Note right of YourScript: retrieveDataAndProof(abiEncodedRequest, roundId)<br/>URL: coston2-data-availability.flare.network/api/v1/fdc/proof-by-request-round-raw
    
    DALayer->>YourScript: 11. Return proof (response_hex + merkle_proof)
    Note left of DALayer: Returns:<br/>- response_hex: processed data<br/>- proof: merkle proof array
    
    YourScript->>SmartContract: 12. Deploy contract
    Note right of YourScript: StarWarsCharacterListV2.new()
    
    YourScript->>SmartContract: 13. Call addCharacter() with proof
    Note right of YourScript: characterList.addCharacter({<br/>merkleProof: proof.proof,<br/>data: decodedResponse<br/>})
    
    SmartContract->>FdcVerification: 14. Verify proof validity
    Note right of SmartContract: ContractRegistry.getFdcVerification()<br/>.verifyJsonApi(_proof)
    
    FdcVerification->>SmartContract: 15. Proof verification result
    Note left of FdcVerification: Returns true if proof is valid
    
    SmartContract->>SmartContract: 16. Calculate BMI & store data
    Note right of SmartContract: bmi = (mass * 100 * 100) / (height * height)<br/>Store: {name: "R2-D2", numberOfMovies: 6,<br/>apiUid: 3, bmi: 34}
    
    SmartContract->>YourScript: 17. Return stored characters
    Note left of SmartContract: getAllCharacters() returns<br/>processed character data with calculated BMI
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Step-by-Step Explanation of the flow:

  1. Request Preparation: Script sends Star Wars API URL and processing rules to FDC verifier server
  2. Encode Request: Server creates encoded attestation request
  3. Submit to FDC Hub: Encoded request submitted to FDC Hub contract on Flare blockchain
  4. Voting Round: Validators fetch data from Star Wars API during voting round
  5. Verify & Vote: Validators verify the data and vote on its authenticity
  6. Generate Proof: DA Layer generates cryptographic proof after round finalization
  7. Request Proof: Script requests proof from DA Layer
  8. Return Proof: DA Layer returns the cryptographic proof
  9. Verify & Process: Smart contract verifies proof and calculates BMI from character data
  10. Store Onchain: Enhanced character information stored permanently on Flare blockchain

Check the details of the flow here: https://github.com/TheVictorMunoz/FDC-101/blob/master/CodeDetails.md

Key Components:

  • External API: Source of real-world data (Star Wars API)
  • FDC Verifier Server: Prepares attestation requests
  • FDC Hub Contract: Manages attestation requests and voting rounds
  • Validators: Fetch and verify external data
  • DA Layer: Generates cryptographic proofs
  • Smart Contract: Processes verified data and stores results

Weather Insurance Contracts (full demo soon)

  • Min Temperature Insurance: Insurance against low temperature events
  • Weather ID Verification: Location-based weather data verification
  • Real-time Data: Integration with OpenWeather API

Getting Started

Prerequisites

  • Node.js (v16 or higher)
  • Yarn package manager
  • Flare testnet tokens (Coston2 faucet)

Installation

  1. Clone the repository:

    git clone https://github.com/TheVictorMunoz/FDC-101.git
cd FDC-101

  2. Install dependencies:

    yarn install

  3. Set up environment:

    cp .env.example .env

  4. Configure your private key: Edit .env file and add your wallet's private key:

    PRIVATE_KEY=your_private_key_here

  5. Get testnet tokens:

    • Visit Coston2 Faucet
    • Enter your wallet address and request C2FLR tokens

Running Examples

Web2Json Example (Star Wars API)

yarn hardhat run scripts/fdcExample/Web2Json.ts --network coston2

This will:

  • Submit an attestation request to FDC Hub
  • Wait for voting round finalization
  • Generate cryptographic proof
  • Deploy smart contract
  • Fetch and display Star Wars character data

Weather Insurance Examples

# Create weather insurance policy
yarn hardhat run scripts/weatherInsurance/weatherId/createPolicy.ts --network coston2

# Resolve weather insurance policy
yarn hardhat run scripts/weatherInsurance/weatherId/resolvePolicy.ts --network coston2

Project Structure

├── contracts/
│   ├── crossChainFdc/          # Cross-chain FDC contracts
│   └── fdcExample/            # FDC example contracts
├── scripts/
│   ├── fdcExample/            # Web2Json and FDC examples
│   ├── weatherInsurance/      # Weather insurance contracts
│   ├── proofOfReserves/       # Proof of reserves functionality
│   └── utils/                 # Utility functions
├── utils/                     # Network utilities
└── hardhat.config.ts         # Hardhat configuration

Configuration

Supported Networks

  • Coston2 Testnet (Chain ID: 114) - Primary testnet
  • Coston Testnet (Chain ID: 16)
  • Songbird (Chain ID: 19)
  • Flare Mainnet (Chain ID: 14)

Environment Variables

PRIVATE_KEY=your_wallet_private_key
FLARE_RPC_API_KEY=your_flare_api_key
FLARESCAN_API_KEY=your_flarescan_api_key
OPEN_WEATHER_API_KEY=your_openweather_api_key

FDC Attestation Types and Features

  • Web2Json: HTTP API data fetching and verification
  • Payment Verification: Payment transaction verification
  • Balance Decreasing: Balance change verification
  • Address Validity: Address format verification
  • Block Height: Block existence verification

Example Output

Running the Web2Json example produces:

Star Wars Characters:
[
  [
    'R2-D2',
    '6',
    '3', 
    '34',
    name: 'R2-D2',
    numberOfMovies: '6',
    apiUid: '3',
    bmi: '34'
  ]
]

Useful Links

Contributing

  1. Fork the repository
  2. Create a feature branch
  3. Make your changes
  4. Test thoroughly on testnet
  5. Submit a PR

Deepwiki: https://deepwiki.com/TheVictorMunoz/FDC-101

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