stacchain - smart contract examples

Table of Contents

1. Smart Contracts for the STAC Ecosystem
2. Security Warning
3. Features
4. Repository Structure
5. Prerequisites
6. Getting Started
   1. Clone the Repository
   2. Install Dependencies
   3. Set Up Environment Variables
   4. Compile the Contracts
7. Usage
   1. Deploy Contracts
   2. Run Tests
   3. Verifying Contracts
   4. Project Scripts
8. Key Features
   1. STACToken
   2. STACAccessCode
9. How an External API Validates an Access Code
   1. User Interaction with the API
   2. API Queries the Blockchain
   3. Blockchain Verification
   4. API Grants or Denies Access
10. Example Workflow
    1. Step 1: User Sends Request
    2. Step 2: API Validates the Access Code
    3. Step 3: Grant or Deny Access
11. How the API Identifies a Valid Code
    1. Tied to the User's Address
    2. Tamper-Proof Hash
    3. Expiration Time
12. Advantages of On-Chain Validation
13. License
14. Contributions
15. Contact

Smart Contracts for the STAC Ecosystem

This repository contains smart contracts for the STAC Ecosystem, including:

• STACToken: An ERC20 token for the STAC ecosystem.
• STACAccessKey: A smart contract for purchasing access keys to geospatial data collections using blockchain technology.

Security Warning

1. Private Keys:

   • Never share or hardcode your private keys in the repository or any script. Use environment variables stored in a .env file, which is excluded from version control.
   • Ensure the .env file is secure and accessible only to authorized users.

2. Mainnet Deployment:

   • Be extra cautious when deploying contracts to the Polygon mainnet. Test thoroughly on the Mumbai testnet before deploying to the mainnet.
   • Mistakes on the mainnet can result in irreversible loss of funds.

3. Mumbai Testnet:

   • The Mumbai testnet is a safe environment for testing deployments and interactions. Use free MATIC from a Mumbai Faucet to fund your wallet for testing.

4. Gas Fees:

   • Transactions on Polygon require MATIC for gas fees. Ensure your wallet has enough MATIC to cover the gas costs for deployments and interactions.

Features

• STACToken:
  • ERC20-compliant token implemented using OpenZeppelin.
  • Minted with an initial supply of 1,000,000 tokens.
• STACAccessKey:
  • Allows users to purchase access keys by sending cryptocurrency.
  • Emits events for integration with external systems.
  • Admin controls for revoking access and updating prices.

---

Repository Structure

smart-contracts/
├── contracts/
│   ├── STACToken.sol        # ERC20 token contract
│   ├── STACAccessKey.sol    # Access key contract
├── scripts/
│   ├── deploySTACToken.js   # Deployment script for STACToken
│   ├── deployAccessKey.js   # Deployment script for STACAccessKey
├── test/
│   ├── STACToken.test.js    # Tests for STACToken
│   ├── STACAccessKey.test.js # Tests for STACAccessKey
├── hardhat.config.js        # Hardhat configuration
├── package.json             # Project dependencies and scripts
├── .env                     # Environment variables (excluded from version control)
├── README.md                # Documentation
└── LICENSE                  # Licensing information

Prerequisites

To use this repository, ensure you have the following installed:

• Node.js (v16+ recommended)
• Hardhat
• A Polygon-compatible wallet like MetaMask
• A funded account with MATIC (for gas fees) on the Polygon Mumbai testnet or mainnet.

Getting Started

1. Clone the Repository

git clone https://github.com/your-username/smart-contracts.git
cd smart-contracts

2. Install Dependencies

npm install

3. Set Up Environment Variables

Create a .env file in the root of your project and populate it with the necessary environment variables:

MUMBAI_PRIVATE_KEY=private-key-mumbai-test-net
POLYGON_PRIVATE_KEY=private-key-polygon-network
POLYGONSCAN_API_KEY=polygonscan-api-key

4. Compile the Contracts

Compile the smart contracts to generate artifacts:

npx hardhat compile

Usage

Deploy Contracts

• Deploy STACToken (ERC20 Token)

npx hardhat run scripts/deploySTACToken.js --network mumbai

• Deploy STACAccessKey (Access Key Contract)

npx hardhat run scripts/deployAccessKey.js --network mumbai

Note: Replace mumbai with polygon for deploying to the mainnet.

Run Tests

Test the functionality of the contracts using Hardhat's testing framework:

npx hardhat test

Verifying Contracts

After deployment, verify your contracts on PolygonScan:

npx hardhat verify --network mumbai DEPLOYED_CONTRACT_ADDRESS

Project Scripts

• Compile Contracts:

npm run compile

• Test Contracts:

npm run test

• Deploy to Mumbai Testnet:

npm run deploy:access:mumbai

• Deploy to Polygon Mainnet:

npm run deploy:access:polygon

• Verify Contracts:

npm run verify -- DEPLOYED_CONTRACT_ADDRESS

Key Features

STACToken

• ERC20 Standard: Fully compliant with the ERC20 specification.
• Initial Supply: 1,000,000 tokens minted to the deployer's address.
• Transfer Functionality: Supports standard transfer, approve, and transferFrom.

STACAccessCode

• Access Control: Users can purchase unique access codes using native cryptocurrency (e.g., MATIC). Each code is tied to a specific user and can be reused by the same user for the duration of its validity.
• Event Emission: Emits AccessCodeGenerated and AccessCodeRevoked events for real-time tracking and integration with external systems.
• Admin Features: Contract owners can update access prices, revoke access for users, and withdraw accumulated funds.
• Security:
  • The actual access code is private and not stored on-chain. Only its hashed version is recorded for validation purposes.
  • Ensures that access codes are user-specific and cannot be used by others.
  • Supports time-limited validity for access codes to balance user convenience and security.

How an External API Validates an Access Code

1. User Interaction with the API:

• The user sends their access code and wallet address to the API to request data access.
• Example: The user provides STAC-abc123 as their access code and 0xUserAddress as their wallet address.

2. API Queries the Blockchain:

• The API interacts with the STACAccessCode contract deployed on the blockchain to validate the access code.
• The API uses the following contract function for validation:

function verifyAccessCode(address user, string memory accessCode) external view returns (bool)

• The API provides the user's wallet address (user) and the access code (accessCode) to this function.

3. Blockchain Verification:

• The contract checks:
  • The hash of the provided accessCode matches the stored hash for the user.
  • The access code has not expired (if time-limited).
• The contract returns true if the access code is valid and false otherwise.

4. API Grants or Denies Access:

• If the contract returns true, the API grants access to the requested data.
• If the contract returns false, the API denies access and may return an error message indicating an invalid or expired access code.

Example Workflow

Step 1: User Sends Request

• The user sends the following to the API:

{
  "accessCode": "STAC-abc123",
  "walletAddress": "0xUserAddress"
}

Step 2: API Validates the Access Code

• The API uses a blockchain library (e.g., Ethers.js or Web3.js) to query the contract:

const contract = new ethers.Contract(contractAddress, contractABI, provider);

const isValid = await contract.verifyAccessCode(
  userWalletAddress,
  userProvidedAccessCode
);

if (isValid) {
  // Grant access
  return { success: true, message: "Access granted." };
} else {
  // Deny access
  return { success: false, message: "Invalid or expired access code." };
}

Step 3: Grant or Deny Access

• If the code is valid, the API allows the user to access the requested geospatial data.
• If the code is invalid or expired, the API denies access and informs the user.

How the API Idenitfies a Valid Code

1. Tied to the User's Address:

• The access code is only valid for the wallet address that purchased it.
• The contract checks the combination of the user's wallet address and the provided access code.

2. Tamper-Proof Hash:

• The access code is hashed and stored on-chain. An attacker cannot generate a valid hash without the original access code.

3. Expiration Time:

• If the access code has an expiration period, the contract ensures it is still valid at the time of verification.

Advantages of On-Chain Validation

• Security:
  • The blockchain provides a decentralized and tamper-proof mechanism for validating access codes.
  • Even the API operator cannot forge a valid access code.
• Transparency:
  • Users can verify the validity of their own access codes on-chain.
• Flexibility:
  • The API can validate access codes in real-time without needing to manage its own database of keys.

License

This repository is licensed under the Apache 2.0 License. See the LICENSE file for details.

Contributions

We welcome contributions! Please follow these steps:

• Fork the repository.
• Create a new branch (feature/your-feature-name).
• Commit your changes and open a pull request.

Contact

Have questions or feedback? Reach out to us:

Email: [email protected] GitHub: stacchain Website: https://stacchain.github.io