Anti-Fraud Backend

AI-powered blockchain transaction fraud detection system that analyzes Ethereum transactions in real-time.

Features

• Transaction Analysis: Decodes raw transactions and RPC payloads
• Multi-Chain Support: Ethereum, BSC, Polygon, Arbitrum, Optimism
• ABI Fetching: Automatic contract ABI and source code retrieval from block explorers
• AI-Powered Detection: GPT-4 based fraud analysis with risk scoring
• Function Decoding: Decodes contract function calls with parameters
• Risk Assessment: Provides fraud scores (0-100) and risk levels

API Endpoints

Transaction Analysis

POST /tx/ai-analyze

Request:

{
  "id": "tx_123",
  "method": "eth_sendTransaction",
  "params": [{
    "chainId": "0x38",
    "gas": "0x5208",
    "value": "0xde0b6b3a7640000",
    "from": "0x...",
    "to": "0x...",
    "data": "0x..."
  }]
}

Response:

{
  "success": true,
  "analysis": {
    "type": "contract_interaction",
    "riskLevel": "medium",
    "fraudScore": 65,
    "description": "Contract interaction with potential risks",
    "reasoning": "Detailed AI analysis...",
    "warnings": ["Unverified contract", "High value transfer"],
    "contractInfo": {
      "address": "0x...",
      "abiAvailable": true,
      "sourceCodeAvailable": true
    },
    "aiConfidence": 85
  }
}

Setup

1. Install dependencies:

npm install

2. Environment variables:

OPENAI_API_KEY=your_openai_key
ETHERSCAN_API_KEY=your_etherscan_key

3. Run:

npm run dev

Transaction Types

• ETH Transfer: Simple ETH transfers (low risk)
• Contract Interaction: Smart contract function calls (analyzed by AI)
• Contract Creation: New contract deployments (medium risk)

Tech Stack

• Node.js + TypeScript
• Express.js - REST API
• Viem - Ethereum utilities
• OpenAI GPT-4 - AI fraud analysis
• Etherscan APIs - Contract data fetching

Architecture

1. Transaction Input → JSON payload with transaction data
2. Chain Detection → Identifies blockchain and selects appropriate APIs
3. ABI Fetching → Retrieves contract ABI and source code
4. Function Decoding → Decodes contract calls with parameters
5. AI Analysis → GPT-4 analyzes for fraud patterns
6. Risk Assessment → Returns detailed fraud analysis

Built for hackathon - production ready fraud detection system.