Golden Bridge

A gold-backed ERC-20 token where 1 GLD represents 1 gram of gold.
Users can mint tokens by sending ETH at real-time gold prices using Chainlink Price Feeds.
A 5% fee applies to mint and burn operations — half is allocated to a verifiably fair on-chain lottery powered by Chainlink VRF.
The token also supports cross-chain transfers between Ethereum and Binance Smart Chain (BSC) using Chainlink CCIP, ensuring a secure and seamless bridge while the main implementation remains on Ethereum.

Overview

Golden Bridge demonstrates the integration of multiple advanced smart contract concepts:

• Price oracle usage (Chainlink Price Feed)
• Verifiable randomness (Chainlink VRF)
• Cross-chain communication (Chainlink CCIP)
• On-chain token economics and fee management
• Secure, modular Solidity design following OpenZeppelin standards

This project was built as a personal showcase of Solidity and Web3 development skills, combining real-world token logic with cross-chain interoperability.

Features

• Gold-backed tokenomics — 1 GLD = 1 gram of gold (via Chainlink XAU/USD)
• Real-time minting and burning — ETH-to-gold conversion at live prices
• Fee mechanism (5%) — 50% to lottery pool, 50% to treasury
• On-chain lottery — provably fair draws using Chainlink VRF
• Cross-chain bridge — secure message passing via Chainlink CCIP (Ethereum ↔ BSC)
• Modular architecture — separated contracts for clarity and reusability

Architecture

graph TD
  User((User)) -->|Mint / Burn| GoldToken
  GoldToken -->|Price Data| ChainlinkFeeds[(Chainlink Price Feeds)]
  GoldToken -->|Fee Split| Lotterie
  Lotterie -->|Randomness Request| ChainlinkVRF[(Chainlink VRF)]
  ChainlinkVRF -->|Random Result| Lotterie
  Lotterie -->|Rewards| User
  GoldToken -->|Bridge| TokenBridge
  TokenBridge -->|CCIP Message| CCIPRouter[(Chainlink CCIP Router)]
  CCIPRouter -->|Delivery| RemoteBridge[(TokenBridge on BSC)]
  RemoteBridge -->|GLD Release| RemoteUser((User on BSC))

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Tech Stack

Smart Contracts

• Solidity 0.8.28 (you can probably downgrade the version a few times)
• OpenZeppelin ERC-20 base contracts
• Chainlink VRF, Price Feed, and CCIP integrations

Development & Testing

• Foundry for compilation, deployment, and testing

Project Structure

/src
  ├── GoldToken.sol
  ├── Lotterie.sol
  ├── TokenBridge.sol
  ├── /interfaces
        ├── IGoldToken.sol
        ├── ILotterie.sol
        ├── ITokenBridge.sol
/script
  ├── deployGoldToken.sol
  ├── deployLotterie.s.sol
  ├── deployCoreContracts.s.sol
/test
  ├── GoldToken.fuzz.t.sol
  ├── GoldToken.t.sol
  ├── Lotterie.fuzz.t.sol
  ├── Lotterie.t.sol
  ├── TokenBridge.fuzz.t.sol
  ├── TokenBridge.t.sol
  ├── /mock
        ├── TestLinkToken.sol
        ├── ContractThatRejectsEth.sol

Smart Contract Logic

GoldToken.sol

• Implements ERC-20 standard.
• Uses Chainlink ETH/USD and XAU/USD price feeds for mint/burn calculations.
• Applies 5% fee on mint and burn transactions.
• Distributes fees: 50% to treasury, 50% to Lottery contract.

Lotterie.sol

• Integrates Chainlink VRF v2 for verifiable randomness.
• Pulls the GoldToken user list to determine eligible lottery participants.
• Pays the winning address in GLD from the Lotterie contract balance.

TokenBridge.sol

• Manages CCIP-based cross-chain transfers.
• Locks GLD on the origin chain and releases pre-funded liquidity on the destination chain.
• Handles CCIP message validation, chain/sender whitelists, and replay protection.

Setup & Deployment

# 1. Clone repository
git clone https://github.com/ronfflex/golden-bridge.git
cd Golden-bridge

# 2. Install dependencies
forge install

# 3. Compile contracts
forge build

# 4. Run tests
forge test

# 5. Deploy (example)
forge script script/deployGoldToken.sol --rpc-url $SEPOLIA_RPC --broadcast --verify

Tests & Coverage

All core features (mint, burn, fee distribution, VRF lottery, CCIP bridging) are covered with Foundry tests. A coverage report is generated with:

forge coverage

Tokenomics

Action	Fee	Allocation	Description
Mint / Burn	5%	50% Lotterie, 50% Treasury	Fuels daily lottery rewards and protocol operations

Security Considerations

• Uses Chainlink for trusted off-chain data (no centralized oracles)

• Access control and reentrancy protection via OpenZeppelin modifiers

• Strict validation on bridge transfers and lottery draws

• Tested with edge cases and mocked Chainlink responses

Future Improvements

• Implement OpenZeppelin Defender for automated deploy, upgrades and monitoring

• Implement a frontend dashboard for minting and lottery participation

• Submit for professional security audit

License

MIT License © 2025 - @Vincent Rainaud - @Coralie Boyer

Acknowledgements

• Chainlink for oracles, VRF, and CCIP

• OpenZeppelin for ERC-20 and security patterns

• Foundry for Solidity development and testing tools