smom-dbis-138/docs/operations/CHALLENGER_GUIDE.md

Challenger Operations Guide

Overview

This guide explains how to become a challenger and detect fraudulent claims in the trustless bridge system. Challengers monitor claims and submit fraud proofs to earn rewards.

Becoming a Challenger

Requirements

1. Ethereum Wallet: Wallet with ETH for gas fees
2. Monitoring Infrastructure: Ability to monitor both ChainID 138 and Ethereum Mainnet
3. Technical Knowledge: Understanding of fraud proofs, Merkle proofs, and bridge mechanics
4. Capital: ETH for gas fees (rewards cover costs if successful)

Setup Steps

1. Deploy Monitoring Service:

   • Monitor Deposit events on ChainID 138
   • Monitor ClaimSubmitted events on Ethereum Mainnet
   • Compare claims against source chain state

2. Prepare Fraud Proof Generation:

   • Set up Merkle proof generation
   • Implement fraud proof encoding
   • Test fraud proof verification

3. Test on Testnet:

   • Test challenge submission
   • Verify fraud proof format
   • Practice fraud detection

Challenger Operations

Monitoring for Fraud

What to Monitor:

1. Claims on Ethereum: All ClaimSubmitted events
2. Deposits on ChainID 138: All Deposit events
3. Compare: Verify claims match deposits

Fraud Detection:

• Non-Existent Deposit: Claim for deposit that doesn't exist
• Incorrect Amount: Claim amount differs from actual deposit
• Incorrect Recipient: Claim recipient differs from actual deposit
• Double Spend: Same deposit claimed twice

Submitting Challenges

Function: ChallengeManager.challengeClaim()

Parameters:

• depositId: Deposit ID of the claim to challenge
• proofType: Type of fraud proof (NonExistentDeposit, IncorrectAmount, etc.)
• proof: Encoded fraud proof data

Process:

// Generate fraud proof
bytes memory fraudProof = generateFraudProof(depositId, claim, proofType);

// Submit challenge
challengeManager.challengeClaim(
    depositId,
    proofType,
    fraudProof
);

Fraud Proof Types:

1. NonExistentDeposit: Merkle proof showing deposit doesn't exist
2. IncorrectAmount: Merkle proof with actual deposit amount
3. IncorrectRecipient: Merkle proof with actual recipient
4. DoubleSpend: Proof of previous claim for same deposit

Fraud Proof Generation

Non-Existent Deposit Proof:

1. Get state root from ChainID 138 block
2. Hash claimed deposit data
3. Generate Merkle proof showing non-existence
4. Encode proof according to FraudProofTypes.NonExistentDepositProof

Incorrect Amount Proof:

1. Get actual deposit from ChainID 138
2. Generate Merkle proof for actual deposit
3. Encode proof with actual amount
4. Submit challenge with proof

See: docs/bridge/trustless/FRAUD_PROOFS.md for detailed proof formats

Economics

Costs

• Gas Fees: For submitting challenges
• Infrastructure: Monitoring and proof generation costs
• Time: Time to monitor and generate proofs

Revenue

• Challenger Reward: 50% of slashed bond
• Example: If bond is 1.1 ETH, challenger receives 0.55 ETH

Profitability

• Calculate: Reward - Gas Costs - Infrastructure - Time
• Consider success rate, gas prices, bond amounts
• Monitor market conditions

Best Practices

1. Detection

• Fast Detection: Detect fraud quickly (within challenge window)
• Accurate Proofs: Ensure fraud proofs are correct
• Comprehensive Monitoring: Monitor all claims and deposits
• Pattern Recognition: Identify patterns in fraudulent claims

2. Proof Generation

• Correct Format: Use proper fraud proof encoding
• Valid Proofs: Ensure proofs are verifiable
• Complete Data: Include all required proof elements
• Testing: Test proof generation thoroughly

3. Risk Management

• Gas Costs: Monitor gas prices
• Success Rate: Track challenge success rate
• Competition: Consider other challengers
• Timing: Submit challenges within challenge window

Automation

Automated Monitoring

• Set up event watchers for both chains
• Compare claims against deposits automatically
• Alert on potential fraud
• Generate fraud proofs automatically

Automated Challenging

• Automatically submit challenges when fraud detected
• Optimize gas usage
• Monitor challenge success
• Track rewards

Troubleshooting

Challenge Rejected

• Check Proof: Verify fraud proof is correct
• Verify Format: Ensure proof encoding is correct
• Check Timing: Ensure within challenge window
• Review Errors: Check error messages

Invalid Fraud Proof

• Verify Merkle Proof: Ensure Merkle proof is valid
• Check State Root: Verify state root is correct
• Review Encoding: Check proof encoding format
• Test Locally: Test proof verification locally

High Gas Costs

• Wait: Consider waiting for lower gas prices
• Batch: Batch multiple challenges if possible
• Optimize: Optimize proof generation

Monitoring

Key Metrics

• Challenges Submitted: Total challenges submitted
• Success Rate: Percentage of successful challenges
• Rewards Earned: Total rewards from successful challenges
• Gas Costs: Average gas costs per challenge
• Detection Time: Time to detect fraud

Alerts

• Fraud Detected: Alert when fraud is detected
• Challenge Success: Alert on successful challenges
• Gas Prices: Alert on high gas prices
• Patterns: Alert on fraud patterns

References

• Fraud Proofs: docs/bridge/trustless/FRAUD_PROOFS.md
• Challenge Manager: contracts/bridge/trustless/ChallengeManager.sol
• Architecture: docs/bridge/trustless/ARCHITECTURE.md