Tikka - Decentralized Raffle Platform

🎯 What is Tikka?

Tikka is a decentralized raffle platform built on Stellar using Soroban smart contracts. Users can create raffles, sell tickets priced in Stellar assets, and distribute prizes securely on-chain.

🚀 Key Features

🎲 On-Chain Winner Selection

• Internal draws use Soroban env.prng() with a multi-source seed: timestamp + sequence + raffle_id + tickets_sold
• Deterministic replay for identical raffle and ledger inputs
• Intended for low-stakes raffles; high-stakes draws should use oracle randomness

💰 Token-Based Tickets and Prizes

• Ticket Purchases: Any Stellar asset contract
• Prizes: Same asset used for ticket purchases
• Flexible Pricing: Set ticket prices and prize amount per raffle

🔒 Escrowed Prizes

• Prizes are held in the smart contract until finalization
• Winners claim prizes after the raffle ends

📊 Basic Raffle Analytics

• Total tickets sold per raffle
• Winner tracking and claim status

🏗️ How Tikka Works

1. Raffle Creation

Creator → Create Raffle → Set Parameters

• Raffle creators specify:
  • Description and end time
  • Maximum ticket count
  • Ticket price and payment asset
  • Whether multiple tickets per person are allowed
  • Prize amount (in the same payment asset)

2. Prize Escrow

Creator → Deposit Prize → Contract Escrow

• Prizes are transferred to the smart contract
• Contract holds the prize until raffle finalization

3. Ticket Sales

Participants → Buy Tickets → Contract Validation → Ticket Issuance

• Users purchase tickets with the raffle asset
• Contract validates payment and issues tickets
• One ticket equals one entry in the raffle

4. Winner Selection

Raffle Ends → Finalize → Select Winner

• Winner is selected from sold tickets
• Internal mode uses Soroban PRNG seeded with multiple ledger and raffle fields
• External/oracle mode remains available for stronger trust assumptions

5. Prize Distribution

Winner Selected → Claim Prize

• Winners claim their prizes

Raffle Flow Diagram

flowchart TD
    Creator[Creator]
    Buyer[TicketBuyer]
    Token[StellarAssetContract]
    Raffle[RaffleContract]

    Creator -->|"create_raffle()"| Raffle
    Creator -->|"deposit_prize()"| Token
    Token -->|"transfer(prize)"| Raffle

    Buyer -->|"buy_ticket()"| Token
    Token -->|"transfer(ticket_price)"| Raffle

    Raffle -->|"finalize_raffle()"| Raffle
    Raffle -->|"select_winner(prng_seeded_entropy)"| Raffle

    Buyer -->|"claim_prize()"| Raffle
    Raffle -->|"transfer(prize)"| Token
    Token -->|"transfer(prize)"| Buyer

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🔧 Technical Architecture

Smart Contract Stack

• Soroban (Rust): Smart contract implementation
• Stellar: Network and asset contracts

Core Contract

contracts/hello-world/src/lib.rs

pub fn create_raffle(... ) -> u64;
pub fn deposit_prize(... );
pub fn buy_ticket(... ) -> u32;
pub fn finalize_raffle(... ) -> Address;
pub fn claim_prize(... );
pub fn get_raffle(... ) -> Raffle;
pub fn get_tickets(... ) -> Vec<Address>;

Data Structures

pub struct Raffle {
    pub id: u64,
    pub creator: Address,
    pub description: String,
    pub end_time: u64,
    pub max_tickets: u32,
    pub allow_multiple: bool,
    pub ticket_price: i128,
    pub payment_token: Address,
    pub prize_amount: i128,
    pub tickets_sold: u32,
    pub is_active: bool,
    pub prize_deposited: bool,
    pub prize_claimed: bool,
    pub winner: Option<Address>,
}

Contract Constraints (Demo)

• Only one winner per raffle
• Prize and ticket payments use the same Stellar asset
• Internal PRNG is suitable for low-stakes raffles (e.g., sub-500 XLM prizes)
• For high-stakes raffles, prefer the external oracle/VRF randomness path

🔒 Metadata Integrity (metadata_hash)

Every raffle requires a metadata_hash: BytesN<32> — a SHA-256 hash of the off-chain metadata JSON stored on IPFS. This hash is committed on-chain at creation and is immutable, so organizers cannot alter the description, image, or rules after tickets are sold.

Metadata JSON format

{
  "name": "My Raffle",
  "description": "Full rules and description here",
  "image": "ipfs://Qm...",
  "rules": "..."
}

Generating the hash

Linux / macOS

# 1. Create your metadata file
cat > metadata.json << 'EOF'
{"name":"My Raffle","description":"...","image":"ipfs://Qm...","rules":"..."}
EOF

# 2. Hash it (outputs hex)
sha256sum metadata.json
# or on macOS:
shasum -a 256 metadata.json

Node.js

const crypto = require("crypto");
const fs = require("fs");
const hash = crypto
  .createHash("sha256")
  .update(fs.readFileSync("metadata.json"))
  .digest("hex");
console.log(hash); // 64-char hex string → 32 bytes

Python

import hashlib, json

meta = {"name": "My Raffle", "description": "...", "image": "ipfs://Qm...", "rules": "..."}
# Use compact, sorted JSON for reproducibility
raw = json.dumps(meta, separators=(',', ':'), sort_keys=True).encode()
print(hashlib.sha256(raw).hexdigest())

Converting hex → BytesN<32> for the contract call

# Stellar CLI example — pass as a hex-encoded bytes argument
stellar contract invoke ... -- \
  --metadata_hash "$(sha256sum metadata.json | cut -d' ' -f1)"

Important: Use a canonical JSON serialization (compact, keys sorted) so the hash is reproducible by anyone who downloads the metadata from IPFS.

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Stellar Testnet

• Contract Address: CCTCPMI66REXIJQPVOPNTNUZBCMSRM7TZLMIPQROZIID44XNP2P2MKFZ

🚀 Getting Started

Prerequisites

• Rust toolchain
• Stellar CLI (optional for deployment)

Run Tests

cargo test -p hello-world

Build the Contract

cargo build -p hello-world

🛠️ Development

For local setup, build, and test workflows, see DEVELOPMENT.md.

🤝 Contributing

See CONTRIBUTING.md for contribution guidelines and PR expectations.

📚 Documentation

• Stellar Soroban: https://developers.stellar.org/docs/build/smart-contracts/overview
• Soroban Examples: https://github.com/stellar/soroban-examples

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🆘 Support

• Documentation: Check our guides
• Issues: Report bugs and feature requests
• Community: Join our Discord for discussions

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