This implementation uses AES-256-GCM with scrypt key derivation for encrypting private keys. Here's why this is secure and recommendations for production use.

1. AES-256-GCM Encryption

   • Industry standard symmetric encryption
   • 256-bit key length (virtually unbreakable)
   • Built-in authentication (prevents tampering)
   • Galois/Counter Mode for performance

2. Scrypt Key Derivation

   • Memory-hard function (resistant to ASICs)
   • Configurable cost parameters
   • Better than PBKDF2 for password-based keys
   • Standard in cryptocurrency applications

3. Cryptographically Secure Randomness

   • crypto.randomBytes() for salts and IVs
   • Each encryption uses unique salt and IV
   • No predictable patterns

4. Multiple Security Layers

   • User password + User ID for master password
   • Additional ENCRYPTION_SECRET from environment
   • Separate encryption for each user

# Use strong, unique secrets
ENCRYPTION_SECRET=$(openssl rand -base64 32)
JWT_SECRET=$(openssl rand -base64 64)

# Separate secrets per environment
ENCRYPTION_SECRET_DEV=xxx
ENCRYPTION_SECRET_STAGING=yyy  
ENCRYPTION_SECRET_PROD=zzz

class KeyRotationService {
  static async rotateEncryptionKeys() {
    // 1. Generate new encryption secret
    // 2. Re-encrypt all private keys with new secret
    // 3. Update environment variables
    // 4. Invalidate old keys after grace period
  }
}

import rateLimit from 'express-rate-limit';

const walletExportLimit = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 3, // Only 3 private key exports per 15 minutes
  message: 'Too many private key export attempts'
});

class SecurityLogger {
  static logPrivateKeyAccess(userId, action, success, ipAddress) {
    console.log(JSON.stringify({
      timestamp: new Date().toISOString(),
      userId,
      action, // 'export', 'import', 'encrypt', 'decrypt'
      success,
      ipAddress,
      severity: 'HIGH'
    }));
  }
}

class MFAService {
  static async requireMFAForPrivateKey(userId) {
    // Require 2FA before allowing private key operations
    const user = await User.findByPk(userId);
    if (!user.mfaEnabled) {
      throw new Error('MFA required for private key operations');
    }
    
    // Verify TOTP/SMS code
    return await this.verifyMFAToken(user.mfaSecret, mfaToken);
  }
}

• Use strong, unique ENCRYPTION_SECRET (min 32 bytes)
• Implement proper key rotation strategy
• Add rate limiting on private key operations
• Enable comprehensive audit logging
• Use HTTPS everywhere
• Implement MFA for sensitive operations
• Regular security audits and penetration testing
• Secure environment variable management
• Database encryption at rest
• Proper backup and disaster recovery

1. Never log private keys or encryption secrets
2. Use separate encryption keys per environment
3. Implement proper session management
4. Regular dependency updates and security scanning
5. Input validation and sanitization everywhere
6. Implement proper CORS policies
7. Use security headers (helmet.js)
8. Regular security training for development team

class SecurityMonitoring {
  static monitorSuspiciousActivity() {
    // Alert on:
    // - Multiple failed private key decryption attempts
    // - Private key exports from unusual locations
    // - Bulk wallet operations
    // - Unusual API usage patterns
  }
}

• OWASP Cryptographic Storage Cheat Sheet
• NIST Cryptographic Standards
• Web3 Security Best Practices

For Production Use:

1. Keep current implementation - it's already very secure
2. Add HSM/KMS for enterprise-level security
3. Implement MFA for private key operations
4. Add comprehensive monitoring and alerting
5. Regular security audits and penetration testing

The current implementation with AES-256-GCM and scrypt is production-ready and follows industry best practices. The additional recommendations are for enhanced security in high-value applications.