LP-6019: Bridge Security Framework

Abstract

The Bridge Security Framework establishes comprehensive security standards and procedures for all cross-chain bridge operations within the Lux ecosystem. This LP defines security requirements for bridge implementations, monitoring systems, incident response procedures, and ongoing security maintenance. It applies to both the MPC Bridge (LP-15) and Teleport (LP-16) protocols, as well as future bridge implementations.

Motivation

Bridge security is critical because bridges:

Hold Significant Value: Billions in assets flow through bridges
Are Primary Attack Targets: Most major DeFi hacks involve bridges
Have Complex Attack Surfaces: Multiple chains, validators, and protocols
Require Coordinated Response: Security incidents need rapid, organized action
Need Continuous Monitoring: Threats evolve and require ongoing vigilance

This framework ensures all Lux bridges maintain the highest security standards and can respond effectively to threats.

Specification

Security Architecture

Defense in Depth Model

Layer 1: Protocol Security
- Cryptographic primitives
- Consensus mechanisms
- Smart contract security

Layer 2: Operational Security  
- Key management
- Access controls
- Monitoring systems

Layer 3: Economic Security
- Stake requirements
- Insurance funds
- Slashing mechanisms

Layer 4: Governance Security
- Emergency procedures
- Upgrade processes
- Incident response

Security Requirements

1. Cryptographic Standards

interface ICryptoStandards {
    // Minimum key sizes
    uint256 constant MIN_RSA_KEY_SIZE = 2048;
    uint256 constant MIN_ECDSA_KEY_SIZE = 256;
    
    // Approved algorithms
    enum HashAlgorithm { SHA256, SHA3_256, KECCAK256 }
    enum SignatureAlgorithm { ECDSA_SECP256K1, BLS12_381 }
    
    // Key rotation requirements
    uint256 constant MAX_KEY_AGE = 365 days;
    uint256 constant KEY_ROTATION_NOTICE = 30 days;
}

2. Validator Security

struct ValidatorRequirements {
    uint256 minStake;              // Minimum stake amount
    uint256 minUptime;             // Required uptime percentage
    bool hardwareSecurityModule;   // HSM requirement
    bool secureEnclave;            // TEE/SGX requirement
    uint256 slashingThreshold;     // Misbehavior threshold
}

3. Smart Contract Security

Audit Requirements: Two independent audits before mainnet
Formal Verification: Critical functions must be formally verified
Upgrade Procedures: Time-locked upgrades with governance approval
Emergency Pause: Ability to halt operations within 15 minutes

Monitoring and Detection

1. Real-Time Monitoring

interface IBridgeMonitor {
    struct MonitoringMetrics {
        uint256 totalValueLocked;
        uint256 dailyVolume;
        uint256 largestTransfer;
        uint256 failedTransactions;
        uint256 pendingTransactions;
        uint256 averageConfirmationTime;
    }
    
    function getMetrics() external view returns (MonitoringMetrics memory);
    function checkHealthStatus() external view returns (bool healthy, string memory issue);
}

2. Anomaly Detection

Detection Rules:
  - Unusual Volume: > 5x daily average
  - Large Transfer: > $10M single transaction
  - Rapid Withdrawals: > 10% TVL in 1 hour
  - Failed Transactions: > 5% failure rate
  - Validator Issues: < 80% participation
  - Gas Anomalies: > 3x normal gas usage

3. Alert System

enum AlertSeverity { INFO, WARNING, CRITICAL, EMERGENCY }

struct SecurityAlert {
    AlertSeverity severity;
    string alertType;
    bytes32 transactionHash;
    uint256 timestamp;
    string description;
    bytes additionalData;
}

Incident Response

1. Response Procedures

EMERGENCY RESPONSE FLOWCHART:

1. Detection (0-5 minutes)
   ├── Automated monitoring alert
   ├── Manual report
   └── On-chain anomaly

2. Assessment (5-15 minutes)
   ├── Verify incident
   ├── Determine severity
   └── Estimate impact

3. Containment (15-30 minutes)
   ├── Pause affected bridges
   ├── Freeze suspicious accounts
   └── Alert validators

4. Investigation (30-120 minutes)
   ├── Root cause analysis
   ├── Impact assessment
   └── Evidence collection

5. Recovery (2-24 hours)
   ├── Patch vulnerabilities
   ├── Restore operations
   └── Process refunds

6. Post-Mortem (24-72 hours)
   ├── Full incident report
   ├── Lessons learned
   └── Process improvements

2. Emergency Roles

contract EmergencyRoles {
    mapping(address => bool) public guardians;     // Can pause
    mapping(address => bool) public investigators; // Can freeze accounts
    mapping(address => bool) public operators;     // Can execute fixes
    
    uint256 constant GUARDIAN_THRESHOLD = 3;       // Multi-sig threshold
    uint256 constant PAUSE_DURATION = 24 hours;    // Max pause time
}

Security Audits

1. Audit Schedule

Pre-Launch: Two full audits + formal verification
Quarterly: Focused security review
Annual: Comprehensive audit
Post-Incident: Targeted audit after any security event

2. Audit Scope

Code Audit:
  - Smart contracts
  - Off-chain components
  - Key management systems
  - Monitoring infrastructure

Operational Audit:
  - Access controls
  - Incident procedures
  - Backup systems
  - Communication channels

Economic Audit:
  - Token economics
  - Fee structures
  - Insurance coverage
  - Slashing parameters

Risk Management

1. Risk Categories

enum RiskCategory {
    CRYPTOGRAPHIC,    // Key compromise, algorithm weakness
    OPERATIONAL,      // Human error, system failure
    ECONOMIC,         // Market manipulation, fee exploitation
    GOVERNANCE,       // Malicious proposals, voting attacks
    EXTERNAL          // Chain vulnerabilities, oracle failures
}

2. Risk Mitigation

Cryptographic Risks:
  - Multi-party computation
  - Key rotation policies
  - Hardware security modules
  
Operational Risks:
  - Redundant systems
  - Automated failovers
  - Regular drills

Economic Risks:
  - Dynamic fee adjustment
  - Transfer limits
  - Insurance fund

Governance Risks:
  - Time locks
  - Multi-sig controls
  - Stake requirements

External Risks:
  - Oracle diversity
  - Chain monitoring
  - Fallback mechanisms

Insurance and Recovery

1. Insurance Fund

contract BridgeInsurance {
    uint256 public fundTarget;      // Target insurance amount
    uint256 public fundBalance;     // Current balance
    
    struct Claim {
        address claimant;
        uint256 amount;
        bytes32 incidentId;
        ClaimStatus status;
    }
    
    function fileClaim(uint256 amount, bytes32 incidentId) external;
    function processClaim(uint256 claimId) external onlyGovernance;
}

2. Recovery Procedures

Asset Recovery: Procedures for recovering stolen/stuck funds
State Recovery: Rebuilding state from backups
Communication: User notification protocols

Rationale

Design Philosophy

Prevention First: Focus on preventing incidents rather than just responding
Defense in Depth: Multiple layers of security
Rapid Response: Minimize damage through quick action
Transparency: Open communication about security matters
Continuous Improvement: Learn from incidents and near-misses

Key Trade-offs

Security vs Speed: Prioritize security over transaction speed
Decentralization vs Control: Balance with emergency powers
Transparency vs OpSec: Share info while protecting sensitive details

Backwards Compatibility

This security framework is designed to be applied to existing bridges:

Current bridges can adopt incrementally
Core security features are mandatory
Advanced features can be phased in

Test Cases

Security Drills

Emergency Pause Drill
- Simulate critical vulnerability
- Test pause mechanism
- Verify < 15 minute response
Key Compromise Drill
- Simulate validator key leak
- Test key rotation
- Verify no fund loss
Economic Attack Simulation
- Test against flash loan attacks
- Verify fee manipulation resistance
- Check oracle manipulation defenses

Monitoring Tests

Anomaly Detection
- Generate abnormal patterns
- Verify detection accuracy
- Test alert routing
Incident Response
- Full incident simulation
- Test each response phase
- Measure response times

Reference Implementation

Security Framework: [github.com/luxfi/bridge-security]
Monitoring Tools: [github.com/luxfi/bridge-monitor]
Incident Response: [github.com/luxfi/incident-response]

Implementation

Bridge Components

Bridge Directory: bridge/
- Contracts: bridge/contracts/
- MPC Nodes: bridge/mpc-nodes/ (if present)
- Configuration: bridge/config/

Security Framework Implementation

Source: https://github.com/luxfi/bridge (main bridge repository)
Contract Examples:
- Emergency pause contracts: bridge/contracts/
- Monitoring interfaces: bridge/contracts/
- Insurance fund logic: bridge/contracts/

Monitoring and Incident Response

Monitoring Tools: Docker-based monitoring stack in bridge/
Alert System: Configured via bridge/compose.yml
Health Checks: Implemented in bridge node initialization

Testing

Test Cases: bridge/test/
Security Drills: Runnable scenarios in test directory
Integration Tests: Cross-chain testing configuration

Local Development

cd bridge
docker-compose -f compose.local.yml up -d  # Start local bridge

Security Considerations

This entire LP is about security considerations. Key meta-considerations include:

Framework Maintenance

Regular updates as threat landscape evolves
Incorporation of new attack patterns
Integration of security research findings

Human Factors

Security training for all operators
Clear documentation and runbooks
Regular security awareness updates

Coordination Challenges

Multi-chain incident coordination
Cross-team communication
External stakeholder management

Bridge Security Framework