Decentralized Raffle System

Introduction

Decentralized Raffle System is a blockchain-based smart contract built on Ethereum using Solidity. This contract allows users to participate in a decentralized raffle ticket-purchasing system, where users (buyers) can buy tickets, and an organizer can later draw a winner at random. The winner is granted the ability to withdraw the total collected Ether.

The contract demonstrates key features like:

• Role-based access control (organizers vs. buyers).
• Secure ticket purchasing mechanism.
• Pseudo-random winner selection.
• Secure fund withdrawal by the winner.

This project is a simple and secure solution for decentralized raffle systems, ensuring fairness and transparency through blockchain technology.

Features

• Role-based Access: Users are assigned roles of either Organizer or Buyer.
• Ticket Purchase: Buyers can purchase tickets by sending Ether to the contract.
• Random Winner Selection: The Organizer can draw a winner when all tickets are sold.
• Secure Fund Withdrawal: Only the winner is allowed to withdraw the total collected Ether.
• Blockchain Transparency: Every transaction and role assignment is recorded on the Ethereum blockchain for transparency.

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Smart Contract Functions

1. AssignRole: Assigns a role (Organizer/Buyer) to a user.
2. GetRole: Returns the assigned role of a specific user.
3. getNoOfSoldTickets: Returns the total number of tickets sold.
4. getNoOfAvailableTickets: Returns the number of tickets still available.
5. purchaseTicket: Allows a buyer to purchase a ticket, provided certain conditions are met.
6. DrawWinner: The Organizer can draw a random winner after all tickets are sold.
7. getWinner: Allows the Organizer to view the selected winner.
8. WithDrawEther: The winner can withdraw the total Ether collected from ticket sales.

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Project Structure

• Solidity Version: 0.8.0
• Ethereum Network: Compatible with any Ethereum-based network.
• Remix IDE: This project is easily deployable and executable in the Remix Ethereum IDE.

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How to Run the Project

Prerequisites

• Remix IDE: The contract is designed to be deployed and tested using Remix.

OR

• MetaMask: Install and configure MetaMask to connect to the Ethereum test network.
• Test Ether: Use a faucet to get test Ether on your chosen network (Ropsten, Rinkeby, etc.).

Steps to Run

1. Clone the Repository:
   Clone the GitHub repository where the smart contract is stored:

   git clone https://github.com/codeterrayt/Decentralized-Raffle-System.git

2. Open Remix IDE:
   Go to Remix, an online Solidity IDE.

3. Load the Contract:

   • In Remix, click on the File Explorer panel on the left.
   • Create a new file and paste the smart contract code from this repository.

4. Compile the Contract:

   • In Remix, click on the Solidity Compiler icon on the left.
   • Select the Solidity version 0.8.0 and compile the contract.

5. Deploy the Contract:

   • Go to the Deploy & Run Transactions tab.
   • Click on Deploy.

6. Assign Roles:

   • Use the AssignRole function to assign ORGANIZER to your address and assign other users as BUYER.

7. Purchase Tickets:

   • Buyers can call the purchaseTicket function and send exactly 1 Ether to buy a ticket.

8. Draw Winner:

   • Once all tickets are sold, the Organizer can call the DrawWinner function to select a winner.

9. Withdraw Ether:

   • The winner can then call the WithDrawEther function to withdraw the total Ether in the contract.

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Security Considerations

• Role Verification: Only users with the BUYER role can purchase tickets, and only the ORGANIZER can draw a winner or check the winner's address.
• Randomness: The winner selection uses pseudo-randomness from block attributes (timestamp and previous block random seed). While not perfect for high-value lotteries, it is sufficient for small-scale raffles.
• Ether Handling: The contract securely transfers Ether to the winner and ensures the contract has sufficient balance before processing the transfer.

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Conclusion

This project demonstrates how smart contracts on the Ethereum blockchain can enable decentralized and trustless raffle systems. The transparency and immutability of the blockchain ensure fairness, while the role-based access control ensures that only authorized users can perform sensitive actions like drawing the winner and withdrawing the prize.