Network Security & Encryption

Critical security techniques for secure network communication and data protection in mobile applications.

Transport Layer Security (TLS)

TLS Configuration

• Modern TLS Versions:
  • TLS 1.3 requirement for enhanced security
  • Backward compatibility considerations
  • Cipher suite optimization
• Certificate Management:
  • Certificate pinning implementation
  • Certificate validation
  • Fallback strategies
• Perfect Forward Secrecy:
  • Ephemeral key exchange
  • Session security isolation
  • Long-term key protection

Platform-Specific Security

Android Network Security Config

<!-- Android Network Security Config -->
<network-security-config>
    <domain-config>
        <domain includeSubdomains="true">api.example.com</domain>
        <pin-set>
            <pin digest="SHA-256">AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=</pin>
            <pin digest="SHA-256">BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB=</pin>
        </pin-set>
    </domain-config>
    
    <base-config cleartextTrafficPermitted="false">
        <trust-anchors>
            <certificates src="system"/>
        </trust-anchors>
    </base-config>
</network-security-config>

iOS App Transport Security

// iOS TLS Implementation
class SecureNetworkManager {
    private lazy var session: URLSession = {
        let config = URLSessionConfiguration.default
        config.tlsMinimumSupportedProtocolVersion = .TLSv12
        config.tlsMaximumSupportedProtocolVersion = .TLSv13
        return URLSession(
            configuration: config,
            delegate: self,
            delegateQueue: nil
        )
    }()
}

extension SecureNetworkManager: URLSessionDelegate {
    func urlSession(
        _ session: URLSession,
        didReceive challenge: URLAuthenticationChallenge,
        completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void
    ) {
        // Certificate pinning implementation
        guard let serverTrust = challenge.protectionSpace.serverTrust,
              let serverCertificate = SecTrustGetCertificateAtIndex(serverTrust, 0) else {
            completionHandler(.cancelAuthenticationChallenge, nil)
            return
        }
        
        let serverCertData = SecCertificateCopyData(serverCertificate)
        let serverCertHash = sha256(data: CFDataGetBytePtr(serverCertData))
        
        if pinnedHashes.contains(serverCertHash) {
            completionHandler(.useCredential, URLCredential(trust: serverTrust))
        } else {
            completionHandler(.cancelAuthenticationChallenge, nil)
        }
    }
}

Flutter Certificate Verification

// Flutter TLS Configuration
class SecureHttpClient {
  static HttpClient createSecureClient() {
    final client = HttpClient();
    
    client.badCertificateCallback = (cert, host, port) {
      // Custom certificate validation
      return validateCertificate(cert, host, port);
    };
    
    return client;
  }
  
  static bool validateCertificate(X509Certificate cert, String host, int port) {
    // Certificate pinning logic
    final certHash = sha256.convert(cert.der).toString();
    return pinnedCertificates.contains(certHash);
  }
}

Data Encryption

At-Rest Encryption

• Secure Storage Implementation:
  • Encrypted SharedPreferences (Android)
  • Keychain Services (iOS)
  • Flutter Secure Storage
• Key Management:
  • Hardware security modules
  • Biometric key protection
  • Key rotation strategies
• Data Classification:
  • Sensitive data identification
  • Encryption level determination
  • Storage location decisions

In-Transit Encryption

• End-to-End Encryption:
  • Message-level encryption
  • Key exchange protocols
  • Forward secrecy implementation
• Secure WebSocket:
  • WSS protocol usage
  • Custom encryption layers
  • Real-time communication security
• Encrypted API Communication:
  • Request/response encryption
  • JWT token security
  • API key protection

Security Best Practices

API Security

• Token-Based Authentication:
  • JWT implementation
  • Token refresh mechanisms
  • Secure token storage
• OAuth 2.0 Implementation:
  • Authorization code flow
  • PKCE extension
  • Scope management
• API Key Management:
  • Secure key distribution
  • Key rotation
  • Environment-specific keys

Data Protection

• Sensitive Data Handling:
  • PII data encryption
  • Data minimization
  • Secure transmission
• Secure Key Storage:
  • Platform-specific secure storage
  • Hardware-backed keystores
  • Biometric protection
• Memory Protection:
  • Sensitive data cleanup
  • Memory dump protection
  • Anti-debugging measures

Advanced Security Techniques

Certificate Pinning Implementation

// Android Certificate Pinning with OkHttp
class CertificatePinner {
    companion object {
        fun create(): CertificatePinning {
            return CertificatePinning.Builder()
                .add("api.example.com", "sha256/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=")
                .add("api.example.com", "sha256/BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB=")
                .build()
        }
    }
}

val okHttpClient = OkHttpClient.Builder()
    .certificatePinner(CertificatePinner.create())
    .build()

Secure Communication Patterns

• Message Authentication:
  • HMAC verification
  • Digital signatures
  • Integrity checking
• Replay Attack Prevention:
  • Timestamp validation
  • Nonce usage
  • Sequence numbers
• Man-in-the-Middle Protection:
  • Certificate validation
  • Public key pinning
  • Certificate transparency

Security Monitoring

Threat Detection

• Network Anomaly Detection:
  • Unusual traffic patterns
  • Suspicious endpoints
  • Certificate changes
• Security Event Logging:
  • Authentication failures
  • Certificate validation errors
  • Encryption failures

Compliance & Standards

• GDPR Compliance:
  • Data protection requirements
  • User consent management
  • Data portability
• Industry Standards:
  • OWASP Mobile Top 10
  • NIST cybersecurity framework
  • ISO 27001 alignment

Security Testing

• Penetration Testing:
  • Network layer attacks
  • Certificate validation testing
  • Encryption strength testing
• Security Auditing:
  • Code security reviews
  • Dependency vulnerability scanning
  • Configuration validation