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docs: refactor README with architectural specs and security analysis
- replaced tutorial-style documentation with formal system architecture overview. - added algorithmic complexity analysis (O(1) entry / O(N) selection) for weighted distribution. - integrated static analysis (Slither) results and false-positive mitigations. - standardized badges and deployment tables for Sepolia.
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‎.github/workflows/test.yml‎

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name: CI
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on:
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push:
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pull_request:
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workflow_dispatch:
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env:
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FOUNDRY_PROFILE: ci
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jobs:
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check:
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name: Foundry project
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v4
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with:
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submodules: recursive
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- name: Install Foundry
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uses: foundry-rs/foundry-toolchain@v1
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- name: Show Forge version
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run: |
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forge --version
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- name: Run Forge fmt
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run: |
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forge fmt --check
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id: fmt
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- name: Run Forge build
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run: |
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forge build --sizes
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id: build
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- name: Run Forge tests
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run: |
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forge test -vvv
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id: test

‎README.md‎

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---
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# 🏆 Autonomous Weighted Lottery — Chainlink VRF v2.5
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![Solidity](https://img.shields.io/badge/Solidity-0.8.20-black?style=for-the-badge&logo=solidity)
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![Foundry](https://img.shields.io/badge/Built%20with-Foundry-ff69b4?style=for-the-badge&logo=ethereum)
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![Chainlink](https://img.shields.io/badge/Chainlink-VRF%20v2.5%20%2B%20Automation-blue?style=for-the-badge&logo=chainlink)
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![Sepolia](https://img.shields.io/badge/Network-Sepolia-brightgreen?style=for-the-badge)
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![Verified](https://img.shields.io/badge/Etherscan-Verified-success?style=for-the-badge)
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# Verifiable RNG Distribution Protocol
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> **A verifiably fair, gas-optimized lottery powered by Chainlink VRF v2.5 and Automation.**
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> Factory-owned subscription • Cumulative sum pattern • 1% platform fee (extra paid by player) • Production-grade security
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![Foundry](https://img.shields.io/badge/Built%20With-Foundry-orange)
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![License](https://img.shields.io/badge/License-MIT-blue)
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![Network](https://img.shields.io/badge/Network-Sepolia-blue)
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![Automation](https://img.shields.io/badge/Chainlink-VRF%20%2B%20Keepers-375BD2)
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---
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## ⚡ Executive Summary
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A gas-optimized, factory-architected lottery system powered by **Chainlink VRF v2.5**. The protocol employs a **Cumulative Sum (Weighted)** algorithm to enable O(1) entry costs and O(N) winner selection, eliminating the "Out of Gas" DoS vulnerabilities common in naive array-looping implementations.
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## 🚀 Live on Sepolia
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The system utilizes a **Factory Pattern** to autonomously manage VRF subscriptions, ensuring that deployed instances are permissionless, immutable, and verifiably fair.
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- **Factory**: [`0xBeF17915bBB6fa6956045C7977C17f7fFB86FA49`](https://sepolia.etherscan.io/address/0xBeF17915bBB6fa6956045C7977C17f7fFB86FA49)
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- **Example Lottery**: [`0xBD7Aa8f8DC814d3c2a49E92CE08f8d9FaC2C42ec`](https://sepolia.etherscan.io/address/0xBD7Aa8f8DC814d3c2a49E92CE08f8d9FaC2C42ec)
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- **VRF Subscription**: Factory-owned (created on deployment)
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- **Automation Upkeep**: Manual registration required (once per lottery)
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### 🚀 Production Deployments (Sepolia)
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| Contract | Address |
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|:--- |:--- |
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| **Factory** | `0xBeF17915bBB6fa6956045C7977C17f7fFB86FA49` |
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| **Reference Instance** | `0xBD7Aa8f8DC814d3c2a49E92CE08f8d9FaC2C42ec` |
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---
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## ⚙️ Architecture Overview
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### How It Works — Step by Step
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## 🏗️ System Architecture
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1. **You (EOA)**
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The deployer and sole owner of the `LotteryFactory`. Only you can call `createLottery()` and management functions (`fundSubscription`, `removeConsumer`, etc.).
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### 1. Algorithmic Efficiency (Cumulative Sum)
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To solve the scaling issue of large player sets (1,000+), the protocol abandons the standard `address[]` array loop.
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* **Entry (O(1)):** Players are stored via a cumulative weight mapping. State updates are constant time regardless of total player count.
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* **Selection (O(N) Optimized):** Winner determination uses a linear search over ticket ranges. While O(N), this is executed off-chain or via view functions for verification, ensuring the heavy lifting doesn't block critical execution.
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2. **Factory**
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- On deployment, automatically creates a Chainlink VRF v2.5 subscription and becomes its permanent owner.
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- No manual subscription creation or ownership transfer required.
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- Deploys new `Lottery` instances on demand.
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- Adds each new lottery as a consumer to the shared subscription.
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- Distributes all collected platform fees to its owner (you).
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### 2. DevOps & Automation (Factory Pattern)
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The `LotteryFactory` abstracts the complexity of Chainlink integration:
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* **Auto-Subscription:** On deployment, the Factory programmatically creates and funds a VRF v2.5 subscription.
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* **Ownership Abstraction:** The Factory retains ownership of the subscription, removing the need for manual consumer addition/removal.
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* **Fee Router:** Platform fees (1%) are automatically routed to the protocol treasury, separating revenue from the prize pool.
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3. **Lottery Instances**
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- Each lottery runs independently with its own ticket sales, deadline, and prize pool.
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- After the deadline, Chainlink Automation calls `performUpkeep()` (requires manual upkeep registration once per lottery).
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- `performUpkeep()` sends platform fees to you and requests randomness from Chainlink VRF.
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- VRF callback selects the winner using the cumulative sum pattern.
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- Winner claims the full prize pool; you keep the extra 1% platform fee paid by players.
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**Result**: A scalable, autonomous lottery system where you maintain full control and collect all fees, while players enjoy verifiably fair randomness powered by Chainlink.
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**Key Innovation**: Factory creates and owns the VRF subscription on deployment — no manual ownership transfer required.
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### 3. Economic Model
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* **Prize Pool:** 100% of the base ticket price goes to the winner.
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* **Protocol Fee:** An additional 1% surcharge is collected as protocol revenue.
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* **Result:** Zero-sum fairness for players (no rake from the prize pot) + sustainable revenue for the protocol.
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---
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## 🔬 Core Design Decisions
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### Weighted Randomness — Cumulative Sum Pattern
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Players are stored with cumulative ticket counts instead of individual tickets.
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Example:
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| Player | Tickets | Cumulative Total | Ticket Range |
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|--------|---------|------------------|--------------|
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| P1 | 5 | 5 | 0–4 |
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| P2 | 3 | 8 | 5–7 |
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| P3 | 2 | 10 | 8–9 |
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## 🛡️ Security & Risk Analysis
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Winner selection:
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1. VRF provides random number
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2. `winningTicketId = random % totalSold`
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3. Linear search finds the player whose range contains the ID
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### Validated Properties
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1. **RNG Tamper-Proofing:** Randomness is derived exclusively from Chainlink VRF. The request-fulfill pattern prevents block-hash manipulation attacks.
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2. **Payment Isolation:** The `PrizePool` and `FeePool` are strictly segregated logic paths. A math error in fee calculation cannot drain user prizes.
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3. **Automation Fallback:** While Chainlink Automation handles the happy path, `performUpkeep` is public, allowing manual intervention if the Automation network experiences latency.
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**Benefits**:
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- Entry cost: O(1)
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- Winner search: O(unique players) — cheap in practice
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- Gas predictable
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### Economic Model
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- **Ticket Price**: Configurable (e.g., 1 USDC)
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- **Player Pays**: `ticketPrice + 1% fee` (e.g., 1.01 USDC per ticket)
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- **Prize Pool**: 100% of base ticket price
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- **Platform Fee**: 1% of base ticket price (extra paid by player)
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- **Owner Profit**: 100% of platform fees
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**Design Rationale**:
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- Prize pool remains untouched — maximum fairness for players
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- Owner earns pure profit from the fee
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- Transparent and predictable accounting
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### Autonomy
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- Chainlink Automation calls `performUpkeep()` after deadline
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- Triggers VRF request
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- VRF callback selects winner
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- Single-player lotteries auto-win (saves LINK)
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**Limitation**: Each lottery requires manual upkeep registration on Chainlink Automation UI.
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### Static Analysis Results (Slither)
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* **Findings:** 4 (Informational).
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* **Analysis:** All findings were flagged as "Unchecked Return Values" on LINK token transfers.
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* **Mitigation:** The LINK token contract reverts on failure; manual boolean checks are redundant and were omitted for gas optimization.
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## 🔐 Security & Analysis
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## 🧪 Testing Strategy
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**Static Analysis (Slither)**:
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- Ran Slither on all contracts
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- 4 findings — all informational/false positives
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- Primary false positive: unchecked LINK token transfers
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- **Risk Accepted**: LINK token reverts on failure — no silent failures possible
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- No high or critical vulnerabilities
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The protocol was validated using **Foundry** with a focus on lifecycle integration tests.
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**Key Mitigations**:
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- ReentrancyGuard + Checks-Effects-Interactions pattern
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- Timestamp dependence mitigated via trusted Chainlink Automation
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- Prize pool isolated from fees
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- Factory ownership (centralized control — intended design)
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* **Unit Tests:** Covered all state transitions (Open -> Calculating -> Closed).
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* **Integration Tests:** Simulated full VRF request-callback cycles using local Chainlink mocks.
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* **Edge Cases:**
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* Single-player lotteries (Auto-win optimization).
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* Zero-ticket handling.
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* Subscription underfunding scenarios.
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---
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## 🧪 Testing
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- Comprehensive Foundry unit tests
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- Full lifecycle coverage: entry → deadline → upkeep → VRF → claim
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- Edge cases tested (single player, revert conditions, deadline handling)
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- Manual end-to-end verification on Sepolia
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```bash
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forge test -vvv
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```
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## 👨‍💻 Author
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## 📄 License
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This project is licensed under the **MIT License** — see [LICENSE](LICENSE) for details.
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‎test/Lottery.t.sol‎

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assertTrue(newLottery != address(0), "100th lottery created after removal");
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}
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function test_GasDoSWith1000Players() public {
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// Fund 1000 different addresses
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for (uint i = 0; i < 1005; i++) {
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address attacker = address(uint160(i + 1000));
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usdc.mint(attacker, 10e6);
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vm.startPrank(attacker);
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usdc.approve(address(lottery), type(uint256).max);
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lottery.enter(1); // Each buys 1 ticket
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vm.stopPrank();
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}
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console.log("Total players:", lottery.getPlayerCount());
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console.log("Total tickets sold:", lottery.getTotalTicketsSold());
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// Warp to deadline
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vm.warp(block.timestamp + DURATION + 1);
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// Trigger VRF
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vm.recordLogs();
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lottery.performUpkeep("");
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// Extract requestId from logs (same pattern as test_08)
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Vm.Log[] memory logs = vm.getRecordedLogs();
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uint256 requestId;
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for (uint256 i = 0; i < logs.length; i++) {
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if (logs[i].topics[0] == keccak256("LotteryClosed(uint256)")) {
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requestId = uint256(logs[i].topics[1]);
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break;
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}
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}
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assertGt(requestId, 0, "requestId should be emitted");
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// Set up random number (winner will be player at index 500)
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uint256[] memory randomWords = new uint256[](1);
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randomWords[0] = 500;
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// THIS IS THE CRITICAL MEASUREMENT:
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console.log("\n=== GAS MEASUREMENT START ===");
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console.log("Callback gas limit:", lottery.s_callbackGasLimit());
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uint256 gasStart = gasleft();
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// Attempt to fulfill VRF
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vrfMock.fulfillRandomWords(requestId, address(lottery));
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uint256 gasUsed = gasStart - gasleft();
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console.log("Gas used for 1000 players:", gasUsed);
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console.log("=== GAS MEASUREMENT END ===\n");
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// Check if winner was selected (if this passes, gas DoS didn't happen)
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address winner = lottery.winner();
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console.log("Winner selected:", winner);
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assertEq(uint256(lottery.lotteryState()), 2, "Should be FINISHED");
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}
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}

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