Chapter 10: Privacy-Preserving Features and Compliance

Overview

Vektagraf provides comprehensive privacy-preserving features and compliance tools to meet regulatory requirements including GDPR, HIPAA, and SOX. This chapter covers differential privacy, zero-knowledge proofs, data minimization, consent management, and automated compliance reporting.

Learning Objectives

By the end of this chapter, you will understand:

• GDPR, HIPAA, and SOX compliance implementations
• Differential privacy and zero-knowledge proof patterns
• Data minimization and purpose limitation strategies
• Consent management and data portability
• Privacy-preserving analytics and computations
• Automated compliance monitoring and reporting

Prerequisites

• Understanding of security architecture (Chapter 8)
• Knowledge of access control systems (Chapter 9)
• Familiarity with regulatory compliance concepts

Regulatory Compliance Framework

Vektagraf implements a comprehensive compliance framework that addresses multiple regulatory requirements simultaneously.

Compliance Architecture

graph TB
    A[Compliance Framework] --> B[GDPR Module]
    A --> C[HIPAA Module]
    A --> D[SOX Module]
    A --> E[Custom Compliance]
    
    B --> B1[Consent Management]
    B --> B2[Right to be Forgotten]
    B --> B3[Data Portability]
    B --> B4[Privacy by Design]
    
    C --> C1[PHI Protection]
    C --> C2[Access Controls]
    C --> C3[Audit Trails]
    C --> C4[Breach Notification]
    
    D --> D1[Financial Controls]
    D --> D2[Data Integrity]
    D --> D3[Change Management]
    D --> D4[Reporting Controls]
    
    E --> E1[Custom Policies]
    E --> E2[Industry Standards]
    E --> E3[Regional Laws]

Compliance Configuration

{
  "compliance": {
    "frameworks": {
      "gdpr": {
        "enabled": true,
        "dataRetentionPeriod": "7y",
        "consentRequired": true,
        "rightToBeForgotten": true,
        "dataPortability": true,
        "privacyByDesign": true
      },
      "hipaa": {
        "enabled": true,
        "phiEncryption": "required",
        "accessLogging": "comprehensive",
        "breachNotification": "automatic",
        "businessAssociateAgreement": true
      },
      "sox": {
        "enabled": true,
        "financialDataControls": "strict",
        "changeManagement": "required",
        "auditTrails": "immutable",
        "reportingControls": "automated"
      }
    },
    "dataClassification": {
      "pii": ["email", "phone", "address", "ssn"],
      "phi": ["medical_record", "diagnosis", "treatment"],
      "financial": ["account_number", "transaction", "balance"]
    }
  }
}

GDPR Compliance Implementation

Comprehensive GDPR compliance with automated privacy rights management.

GDPR Compliance Manager

import 'package:vektagraf/vektagraf.dart';

// Initialize GDPR compliance manager
final gdprManager = GdprComplianceManager(
  auditLogger: auditLogger,
  consentManager: ConsentManager(),
  dataExportManager: DataExportManager(),
  anonymizationManager: DataAnonymizationManager(),
);

// Configure GDPR settings
final gdprConfig = GdprConfig(
  dataRetentionPeriod: Duration(days: 2555), // 7 years
  consentExpiryPeriod: Duration(days: 365),
  automaticDeletion: true,
  privacyByDesign: true,
  dataMinimization: true,
);

Consent Management

// Implement comprehensive consent management
class ConsentManager {
  final Map<String, Map<String, ConsentRecord>> _consents = {};
  
  Future<void> recordConsent({
    required String userId,
    required String purpose,
    required String dataType,
    required bool granted,
    String? legalBasis,
    Map<String, dynamic>? metadata,
  }) async {
    final consent = ConsentRecord(
      userId: userId,
      purpose: purpose,
      dataType: dataType,
      granted: granted,
      timestamp: DateTime.now(),
      legalBasis: legalBasis ?? 'consent',
      expiresAt: granted 
          ? DateTime.now().add(Duration(days: 365))
          : null,
      metadata: metadata ?? {},
    );
    
    _consents.putIfAbsent(userId, () => {});
    final consentKey = '$purpose:$dataType';
    _consents[userId]![consentKey] = consent;
    
    // Log consent change
    await auditLogger.logOperation(
      eventType: AuditEventType.securityPolicyChange,
      userId: userId,
      action: 'consent_recorded',
      details: {
        'purpose': purpose,
        'dataType': dataType,
        'granted': granted,
        'legalBasis': legalBasis,
      },
    );
  }
  
  Future<bool> hasValidConsent({
    required String userId,
    required String purpose,
    required String dataType,
  }) async {
    final userConsents = _consents[userId];
    if (userConsents == null) return false;
    
    final consentKey = '$purpose:$dataType';
    final consent = userConsents[consentKey];
    
    return consent?.isValid ?? false;
  }
  
  Future<ConsentStatus> getConsentStatus(String userId) async {
    final userConsents = _consents[userId] ?? {};
    
    final activeConsents = <String, ConsentRecord>{};
    final expiredConsents = <String, ConsentRecord>{};
    
    for (final entry in userConsents.entries) {
      if (entry.value.isValid) {
        activeConsents[entry.key] = entry.value;
      } else if (entry.value.isExpired) {
        expiredConsents[entry.key] = entry.value;
      }
    }
    
    return ConsentStatus(
      userId: userId,
      activeConsents: activeConsents,
      expiredConsents: expiredConsents,
      totalConsents: userConsents.length,
    );
  }
}

// Consent record with GDPR compliance
class ConsentRecord {
  final String userId;
  final String purpose;
  final String dataType;
  final bool granted;
  final DateTime timestamp;
  final String legalBasis;
  final DateTime? expiresAt;
  final Map<String, dynamic> metadata;
  
  const ConsentRecord({
    required this.userId,
    required this.purpose,
    required this.dataType,
    required this.granted,
    required this.timestamp,
    required this.legalBasis,
    this.expiresAt,
    this.metadata = const {},
  });
  
  bool get isExpired => expiresAt != null && DateTime.now().isAfter(expiresAt!);
  bool get isValid => granted && !isExpired;
  
  // Legal bases under GDPR Article 6
  static const legalBases = [
    'consent',           // Article 6(1)(a)
    'contract',          // Article 6(1)(b)
    'legal_obligation',  // Article 6(1)(c)
    'vital_interests',   // Article 6(1)(d)
    'public_task',       // Article 6(1)(e)
    'legitimate_interests', // Article 6(1)(f)
  ];
}

Right to be Forgotten

// Implement right to be forgotten (GDPR Article 17)
class RightToBeForgottenHandler {
  final GdprComplianceManager gdprManager;
  final DataAnonymizationManager anonymizationManager;
  
  RightToBeForgottenHandler({
    required this.gdprManager,
    required this.anonymizationManager,
  });
  
  Future<DeletionResult> processForgetRequest({
    required String userId,
    required String requesterId,
    String? reason,
    bool anonymizeInsteadOfDelete = false,
  }) async {
    // Validate request
    final validationResult = await _validateDeletionRequest(userId, reason);
    if (!validationResult.isValid) {
      return DeletionResult(
        success: false,
        reason: validationResult.reason,
        recordsProcessed: 0,
      );
    }
    
    try {
      if (anonymizeInsteadOfDelete) {
        return await _anonymizeUserData(userId);
      } else {
        return await _deleteUserData(userId);
      }
    } catch (e) {
      return DeletionResult(
        success: false,
        reason: 'Deletion failed: $e',
        recordsProcessed: 0,
      );
    }
  }
  
  Future<ValidationResult> _validateDeletionRequest(
    String userId,
    String? reason,
  ) async {
    // Check if user has active legal obligations
    final activeContracts = await _checkActiveContracts(userId);
    if (activeContracts.isNotEmpty) {
      return ValidationResult(
        isValid: false,
        reason: 'Cannot delete: Active contracts exist',
        details: {'contracts': activeContracts},
      );
    }
    
    // Check legal retention requirements
    final retentionRequirements = await _checkRetentionRequirements(userId);
    if (retentionRequirements.isNotEmpty) {
      return ValidationResult(
        isValid: false,
        reason: 'Cannot delete: Legal retention requirements',
        details: {'requirements': retentionRequirements},
      );
    }
    
    return ValidationResult(isValid: true, reason: 'Request validated');
  }
  
  Future<DeletionResult> _deleteUserData(String userId) async {
    var recordsProcessed = 0;
    var recordsDeleted = 0;
    final errors = <String>[];
    
    try {
      // Delete user profile
      await database.users.deleteById(userId);
      recordsProcessed++;
      recordsDeleted++;
      
      // Delete user's content
      final userPosts = await database.posts.findWhere({'userId': userId});
      for (final post in userPosts) {
        await database.posts.delete(post);
        recordsProcessed++;
        recordsDeleted++;
      }
      
      // Delete user's relationships
      await database.relationships.deleteWhere({'userId': userId});
      recordsProcessed += await database.relationships.count({'userId': userId});
      
      // Delete user's sessions
      await sessionManager.terminateAllUserSessions(userId);
      
      return DeletionResult(
        success: true,
        reason: 'User data successfully deleted',
        recordsProcessed: recordsProcessed,
        recordsDeleted: recordsDeleted,
      );
      
    } catch (e) {
      errors.add(e.toString());
      return DeletionResult(
        success: false,
        reason: 'Deletion failed',
        recordsProcessed: recordsProcessed,
        recordsDeleted: recordsDeleted,
        errors: errors,
      );
    }
  }
  
  Future<DeletionResult> _anonymizeUserData(String userId) async {
    return await anonymizationManager.anonymizeUserData(userId);
  }
}

Data Portability

// Implement data portability (GDPR Article 20)
class DataPortabilityManager {
  Future<DataExportResult> exportUserData({
    required String userId,
    required String requesterId,
    DataExportFormat format = DataExportFormat.json,
    List<String>? includedDataTypes,
  }) async {
    try {
      // Validate export request
      final canExport = await _validateExportRequest(userId, requesterId);
      if (!canExport) {
        return DataExportResult(
          success: false,
          exportId: '',
          recordCount: 0,
          exportSize: 0,
          errors: ['Export request validation failed'],
        );
      }
      
      // Collect user data
      final userData = await _collectUserData(userId, includedDataTypes);
      
      // Format export data
      final exportData = await _formatExportData(userData, format);
      
      // Generate secure download link
      final exportId = _generateExportId(userId);
      final downloadUrl = await _createSecureDownloadLink(exportId, exportData);
      
      return DataExportResult(
        success: true,
        exportId: exportId,
        recordCount: userData.length,
        exportSize: exportData.length,
        downloadUrl: downloadUrl,
        expiresAt: DateTime.now().add(Duration(days: 7)),
      );
      
    } catch (e) {
      return DataExportResult(
        success: false,
        exportId: '',
        recordCount: 0,
        exportSize: 0,
        errors: [e.toString()],
      );
    }
  }
  
  Future<List<Map<String, dynamic>>> _collectUserData(
    String userId,
    List<String>? includedDataTypes,
  ) async {
    final userData = <Map<String, dynamic>>[];
    
    // User profile data
    if (includedDataTypes == null || includedDataTypes.contains('profile')) {
      final user = await database.users.findById(userId);
      if (user != null) {
        userData.add({
          'type': 'profile',
          'data': user.toJson(),
          'collected_at': DateTime.now().toIso8601String(),
        });
      }
    }
    
    // User content data
    if (includedDataTypes == null || includedDataTypes.contains('content')) {
      final posts = await database.posts.findWhere({'userId': userId});
      for (final post in posts) {
        userData.add({
          'type': 'content',
          'subtype': 'post',
          'data': post.toJson(),
          'collected_at': DateTime.now().toIso8601String(),
        });
      }
    }
    
    // User interaction data
    if (includedDataTypes == null || includedDataTypes.contains('interactions')) {
      final interactions = await database.interactions.findWhere({'userId': userId});
      for (final interaction in interactions) {
        userData.add({
          'type': 'interactions',
          'data': interaction.toJson(),
          'collected_at': DateTime.now().toIso8601String(),
        });
      }
    }
    
    return userData;
  }
  
  Future<Uint8List> _formatExportData(
    List<Map<String, dynamic>> userData,
    DataExportFormat format,
  ) async {
    final exportPackage = {
      'export_metadata': {
        'generated_at': DateTime.now().toIso8601String(),
        'format': format.name,
        'record_count': userData.length,
        'gdpr_compliance': true,
        'data_controller': 'Your Organization',
      },
      'user_data': userData,
    };
    
    switch (format) {
      case DataExportFormat.json:
        final jsonString = jsonEncode(exportPackage);
        return Uint8List.fromList(utf8.encode(jsonString));
        
      case DataExportFormat.csv:
        return await _convertToCsv(userData);
        
      case DataExportFormat.xml:
        return await _convertToXml(userData);
    }
  }
}

HIPAA Compliance Implementation

Comprehensive HIPAA compliance for healthcare applications.

PHI Protection

// Protected Health Information (PHI) management
class PhiProtectionManager {
  final EncryptionEngine encryptionEngine;
  final AuditLogger auditLogger;
  
  PhiProtectionManager({
    required this.encryptionEngine,
    required this.auditLogger,
  });
  
  Future<void> configurePhiProtection() async {
    // Configure PHI field encryption
    final phiFields = [
      'medical_record_number',
      'diagnosis',
      'treatment_plan',
      'prescription',
      'lab_results',
      'insurance_info',
    ];
    
    for (final field in phiFields) {
      await _configureFieldEncryption(field, 'AES-256-GCM');
    }
    
    // Configure access controls for PHI
    await _configurePhiAccessControls();
    
    // Configure audit logging for PHI access
    await _configurePhiAuditLogging();
  }
  
  Future<void> _configureFieldEncryption(String fieldName, String algorithm) async {
    final fieldConfig = FieldEncryptionConfig(
      fieldName: fieldName,
      algorithm: algorithm,
      keyRotationInterval: Duration(days: 90),
      accessRoles: ['healthcare_provider', 'authorized_personnel'],
    );
    
    await encryptionManager.configureFieldEncryption(fieldConfig);
  }
  
  Future<void> _configurePhiAccessControls() async {
    // Minimum necessary standard
    final phiAccessPolicy = AccessPolicy(
      name: 'phi_minimum_necessary',
      description: 'HIPAA minimum necessary standard',
      rules: [
        AccessRule(
          condition: 'user.role == "doctor" && resource.patient_id in user.assigned_patients',
          effect: PolicyEffect.allow,
        ),
        AccessRule(
          condition: 'user.role == "nurse" && resource.patient_id in user.assigned_patients',
          effect: PolicyEffect.allow,
          restrictions: ['read_only'],
        ),
        AccessRule(
          condition: 'user.role == "admin" && purpose == "audit"',
          effect: PolicyEffect.allow,
          restrictions: ['audit_only'],
        ),
      ],
    );
    
    await securityEngine.addPolicy(phiAccessPolicy);
  }
}

HIPAA Audit Requirements

// HIPAA-compliant audit logging
class HipaaAuditLogger extends AuditLogger {
  
  Future<void> logPhiAccess({
    required String userId,
    required String patientId,
    required String action,
    required String phiType,
    String? purpose,
    bool success = true,
    String? failureReason,
  }) async {
    await logOperation(
      eventType: AuditEventType.read,
      userId: userId,
      action: 'phi_access',
      resourceType: 'phi',
      resourceId: patientId,
      details: {
        'phi_type': phiType,
        'purpose': purpose,
        'patient_id': patientId,
        'access_method': action,
        if (!success) 'failure_reason': failureReason,
      },
      success: success,
      severity: success ? AuditSeverity.info : AuditSeverity.warning,
    );
  }
  
  Future<void> logPhiDisclosure({
    required String userId,
    required String patientId,
    required String recipientId,
    required String disclosurePurpose,
    required List<String> phiTypes,
    String? authorizationId,
  }) async {
    await logOperation(
      eventType: AuditEventType.dataExport,
      userId: userId,
      action: 'phi_disclosure',
      resourceType: 'phi',
      resourceId: patientId,
      details: {
        'recipient_id': recipientId,
        'purpose': disclosurePurpose,
        'phi_types': phiTypes,
        'authorization_id': authorizationId,
        'disclosure_date': DateTime.now().toIso8601String(),
      },
      severity: AuditSeverity.warning,
    );
  }
  
  Future<HipaaAuditReport> generateHipaaAuditReport({
    DateTime? startDate,
    DateTime? endDate,
    String? patientId,
  }) async {
    final start = startDate ?? DateTime.now().subtract(Duration(days: 30));
    final end = endDate ?? DateTime.now();
    
    // Get PHI access logs
    final phiAccessLogs = await queryLogs(
      startTime: start,
      endTime: end,
      limit: 10000,
    );
    
    final phiLogs = phiAccessLogs
        .where((log) => log.action == 'phi_access')
        .toList();
    
    // Get PHI disclosure logs
    final disclosureLogs = phiAccessLogs
        .where((log) => log.action == 'phi_disclosure')
        .toList();
    
    return HipaaAuditReport(
      reportId: _generateReportId(),
      generatedAt: DateTime.now(),
      periodStart: start,
      periodEnd: end,
      phiAccessCount: phiLogs.length,
      phiDisclosureCount: disclosureLogs.length,
      uniqueUsersAccessed: phiLogs.map((log) => log.userId).toSet().length,
      uniquePatientsAccessed: phiLogs
          .map((log) => log.details['patient_id'] as String?)
          .where((id) => id != null)
          .toSet()
          .length,
      accessByPurpose: _analyzeAccessByPurpose(phiLogs),
      unauthorizedAccessAttempts: phiLogs.where((log) => !log.success).length,
    );
  }
}

Breach Notification

// HIPAA breach notification system
class HipaaBreachNotificationManager {
  final AuditLogger auditLogger;
  final NotificationService notificationService;
  
  HipaaBreachNotificationManager({
    required this.auditLogger,
    required this.notificationService,
  });
  
  Future<void> detectAndNotifyBreaches() async {
    final potentialBreaches = await _detectPotentialBreaches();
    
    for (final breach in potentialBreaches) {
      await _assessBreachRisk(breach);
      
      if (breach.requiresNotification) {
        await _initiateBreachNotification(breach);
      }
    }
  }
  
  Future<List<PotentialBreach>> _detectPotentialBreaches() async {
    final breaches = <PotentialBreach>[];
    
    // Detect unauthorized access attempts
    final unauthorizedAccess = await auditLogger.queryLogs(
      eventType: AuditEventType.permissionDenied,
      startTime: DateTime.now().subtract(Duration(hours: 24)),
    );
    
    final phiUnauthorizedAccess = unauthorizedAccess
        .where((log) => log.resourceType == 'phi')
        .toList();
    
    if (phiUnauthorizedAccess.length > 10) {
      breaches.add(PotentialBreach(
        type: BreachType.unauthorizedAccess,
        severity: BreachSeverity.high,
        affectedRecords: phiUnauthorizedAccess.length,
        detectedAt: DateTime.now(),
        description: 'Multiple unauthorized PHI access attempts detected',
      ));
    }
    
    // Detect unusual data export patterns
    final dataExports = await auditLogger.queryLogs(
      eventType: AuditEventType.dataExport,
      startTime: DateTime.now().subtract(Duration(hours: 24)),
    );
    
    final largeExports = dataExports
        .where((log) => (log.details['record_count'] as int? ?? 0) > 1000)
        .toList();
    
    if (largeExports.isNotEmpty) {
      breaches.add(PotentialBreach(
        type: BreachType.dataExfiltration,
        severity: BreachSeverity.medium,
        affectedRecords: largeExports
            .map((log) => log.details['record_count'] as int? ?? 0)
            .reduce((a, b) => a + b),
        detectedAt: DateTime.now(),
        description: 'Unusual large data export pattern detected',
      ));
    }
    
    return breaches;
  }
  
  Future<void> _initiateBreachNotification(PotentialBreach breach) async {
    // Notify covered entity within 60 days (HIPAA requirement)
    await notificationService.sendBreachNotification(
      recipients: ['privacy_officer@organization.com', 'compliance@organization.com'],
      breach: breach,
      deadline: DateTime.now().add(Duration(days: 60)),
    );
    
    // Log breach notification
    await auditLogger.logOperation(
      eventType: AuditEventType.securityPolicyChange,
      userId: 'system',
      action: 'breach_notification_initiated',
      details: {
        'breach_type': breach.type.name,
        'severity': breach.severity.name,
        'affected_records': breach.affectedRecords,
        'notification_deadline': DateTime.now().add(Duration(days: 60)).toIso8601String(),
      },
      severity: AuditSeverity.critical,
    );
  }
}

SOX Compliance Implementation

Sarbanes-Oxley compliance for financial data integrity and controls.

Financial Data Controls

// SOX-compliant financial data controls
class SoxComplianceManager {
  final AuditLogger auditLogger;
  final ChangeManagementSystem changeManager;
  
  SoxComplianceManager({
    required this.auditLogger,
    required this.changeManager,
  });
  
  Future<void> configureFinancialDataControls() async {
    // Configure immutable audit trails
    await _configureImmutableAuditTrails();
    
    // Configure segregation of duties
    await _configureSegregationOfDuties();
    
    // Configure change management controls
    await _configureChangeManagementControls();
    
    // Configure automated reporting controls
    await _configureReportingControls();
  }
  
  Future<void> _configureImmutableAuditTrails() async {
    final financialAuditConfig = AuditConfig(
      immutableLogs: true,
      cryptographicIntegrity: true,
      tamperDetection: true,
      retentionPeriod: Duration(days: 2555), // 7 years
      backupStrategy: BackupStrategy.multipleLocations,
    );
    
    await auditLogger.configureFinancialAudit(financialAuditConfig);
  }
  
  Future<void> _configureSegregationOfDuties() async {
    final sodPolicies = [
      SodPolicy(
        name: 'financial_transaction_approval',
        description: 'Separate transaction creation and approval',
        conflictingRoles: ['transaction_creator', 'transaction_approver'],
        requiredApprovals: 2,
      ),
      SodPolicy(
        name: 'financial_reporting',
        description: 'Separate report preparation and review',
        conflictingRoles: ['report_preparer', 'report_reviewer'],
        requiredApprovals: 1,
      ),
    ];
    
    for (final policy in sodPolicies) {
      await securityEngine.addSodPolicy(policy);
    }
  }
}

Change Management Controls

// SOX change management system
class ChangeManagementSystem {
  final AuditLogger auditLogger;
  
  Future<ChangeRequest> submitChangeRequest({
    required String requesterId,
    required String changeType,
    required String description,
    required Map<String, dynamic> changeDetails,
    String? businessJustification,
    DateTime? requestedImplementationDate,
  }) async {
    final changeRequest = ChangeRequest(
      id: _generateChangeId(),
      requesterId: requesterId,
      changeType: changeType,
      description: description,
      changeDetails: changeDetails,
      businessJustification: businessJustification,
      requestedDate: requestedImplementationDate,
      status: ChangeStatus.submitted,
      submittedAt: DateTime.now(),
    );
    
    // Log change request submission
    await auditLogger.logOperation(
      eventType: AuditEventType.securityPolicyChange,
      userId: requesterId,
      action: 'change_request_submitted',
      details: {
        'change_id': changeRequest.id,
        'change_type': changeType,
        'description': description,
      },
      severity: AuditSeverity.info,
    );
    
    // Initiate approval workflow
    await _initiateApprovalWorkflow(changeRequest);
    
    return changeRequest;
  }
  
  Future<void> _initiateApprovalWorkflow(ChangeRequest changeRequest) async {
    final approvalWorkflow = ApprovalWorkflow(
      changeRequestId: changeRequest.id,
      requiredApprovers: _getRequiredApprovers(changeRequest.changeType),
      approvalDeadline: DateTime.now().add(Duration(days: 5)),
    );
    
    await _startApprovalProcess(approvalWorkflow);
  }
  
  List<String> _getRequiredApprovers(String changeType) {
    switch (changeType) {
      case 'financial_system':
        return ['cfo', 'it_director', 'compliance_officer'];
      case 'security_policy':
        return ['ciso', 'legal_counsel'];
      case 'database_schema':
        return ['dba', 'application_owner'];
      default:
        return ['manager'];
    }
  }
}

Differential Privacy

Implement differential privacy for privacy-preserving analytics.

Differential Privacy Implementation

// Differential privacy for statistical queries
class DifferentialPrivacyManager {
  final double epsilon; // Privacy budget
  final double delta;   // Failure probability
  
  DifferentialPrivacyManager({
    this.epsilon = 1.0,
    this.delta = 1e-5,
  });
  
  Future<double> privateMean(List<double> values, {
    double sensitivity = 1.0,
  }) async {
    final actualMean = values.reduce((a, b) => a + b) / values.length;
    final noise = _generateLaplaceNoise(sensitivity / epsilon);
    
    return actualMean + noise;
  }
  
  Future<int> privateCount(List<dynamic> values, {
    bool Function(dynamic)? predicate,
  }) async {
    final actualCount = predicate != null 
        ? values.where(predicate).length 
        : values.length;
    
    final noise = _generateLaplaceNoise(1.0 / epsilon);
    final noisyCount = actualCount + noise.round();
    
    return math.max(0, noisyCount); // Ensure non-negative
  }
  
  Future<Map<String, int>> privateHistogram(
    List<String> values,
    List<String> bins,
  ) async {
    final histogram = <String, int>{};
    
    // Initialize bins
    for (final bin in bins) {
      histogram[bin] = 0;
    }
    
    // Count actual values
    for (final value in values) {
      if (histogram.containsKey(value)) {
        histogram[value] = histogram[value]! + 1;
      }
    }
    
    // Add noise to each bin
    final noisyHistogram = <String, int>{};
    for (final entry in histogram.entries) {
      final noise = _generateLaplaceNoise(1.0 / epsilon);
      final noisyCount = entry.value + noise.round();
      noisyHistogram[entry.key] = math.max(0, noisyCount);
    }
    
    return noisyHistogram;
  }
  
  double _generateLaplaceNoise(double scale) {
    final random = Random.secure();
    final u = random.nextDouble() - 0.5;
    return -scale * (u >= 0 ? 1 : -1) * math.log(1 - 2 * u.abs());
  }
  
  Future<List<double>> privateVectorSum(
    List<List<double>> vectors, {
    double sensitivity = 1.0,
  }) async {
    if (vectors.isEmpty) return [];
    
    final dimensions = vectors.first.length;
    final sum = List<double>.filled(dimensions, 0.0);
    
    // Compute actual sum
    for (final vector in vectors) {
      for (int i = 0; i < dimensions; i++) {
        sum[i] += vector[i];
      }
    }
    
    // Add noise to each dimension
    for (int i = 0; i < dimensions; i++) {
      final noise = _generateLaplaceNoise(sensitivity / epsilon);
      sum[i] += noise;
    }
    
    return sum;
  }
}

Privacy-Preserving Analytics

// Privacy-preserving analytics engine
class PrivacyPreservingAnalytics {
  final DifferentialPrivacyManager dpManager;
  final HomomorphicEncryption heManager;
  
  PrivacyPreservingAnalytics({
    required this.dpManager,
    required this.heManager,
  });
  
  Future<AnalyticsResult> computePrivateStatistics({
    required String query,
    required Map<String, dynamic> parameters,
    required double privacyBudget,
  }) async {
    switch (query) {
      case 'user_demographics':
        return await _computeUserDemographics(parameters, privacyBudget);
      
      case 'revenue_analysis':
        return await _computeRevenueAnalysis(parameters, privacyBudget);
      
      case 'user_behavior':
        return await _computeUserBehavior(parameters, privacyBudget);
      
      default:
        throw ArgumentError('Unsupported query type: $query');
    }
  }
  
  Future<AnalyticsResult> _computeUserDemographics(
    Map<String, dynamic> parameters,
    double privacyBudget,
  ) async {
    // Get user data (encrypted)
    final users = await database.users.findAll();
    
    // Extract age groups with differential privacy
    final ageGroups = users.map((user) {
      final age = user.age ?? 0;
      if (age < 18) return 'under_18';
      if (age < 25) return '18_24';
      if (age < 35) return '25_34';
      if (age < 45) return '35_44';
      if (age < 55) return '45_54';
      return '55_plus';
    }).toList();
    
    final ageDistribution = await dpManager.privateHistogram(
      ageGroups,
      ['under_18', '18_24', '25_34', '35_44', '45_54', '55_plus'],
    );
    
    // Extract gender distribution with differential privacy
    final genders = users
        .map((user) => user.gender ?? 'not_specified')
        .toList();
    
    final genderDistribution = await dpManager.privateHistogram(
      genders,
      ['male', 'female', 'other', 'not_specified'],
    );
    
    return AnalyticsResult(
      query: 'user_demographics',
      results: {
        'age_distribution': ageDistribution,
        'gender_distribution': genderDistribution,
        'total_users': await dpManager.privateCount(users),
      },
      privacyBudgetUsed: privacyBudget,
      metadata: {
        'epsilon': dpManager.epsilon,
        'delta': dpManager.delta,
        'computed_at': DateTime.now().toIso8601String(),
      },
    );
  }
  
  Future<AnalyticsResult> _computeRevenueAnalysis(
    Map<String, dynamic> parameters,
    double privacyBudget,
  ) async {
    // Get transaction data
    final transactions = await database.transactions.findAll();
    
    // Compute private revenue statistics
    final amounts = transactions.map((t) => t.amount).toList();
    
    final totalRevenue = amounts.reduce((a, b) => a + b);
    final privateTotal = await dpManager.privateMean(amounts) * amounts.length;
    
    final averageTransaction = await dpManager.privateMean(amounts);
    
    // Monthly revenue distribution
    final monthlyRevenue = <String, double>{};
    for (final transaction in transactions) {
      final month = '${transaction.createdAt.year}-${transaction.createdAt.month.toString().padLeft(2, '0')}';
      monthlyRevenue[month] = (monthlyRevenue[month] ?? 0) + transaction.amount;
    }
    
    final privateMonthlyRevenue = <String, double>{};
    for (final entry in monthlyRevenue.entries) {
      final noise = dpManager._generateLaplaceNoise(1000.0 / dpManager.epsilon);
      privateMonthlyRevenue[entry.key] = math.max(0, entry.value + noise);
    }
    
    return AnalyticsResult(
      query: 'revenue_analysis',
      results: {
        'total_revenue': privateTotal,
        'average_transaction': averageTransaction,
        'monthly_revenue': privateMonthlyRevenue,
        'transaction_count': await dpManager.privateCount(transactions),
      },
      privacyBudgetUsed: privacyBudget,
    );
  }
}

Zero-Knowledge Proofs

Implement zero-knowledge proofs for privacy-preserving verification.

ZK Proof Implementation

// Zero-knowledge proof system
class ZeroKnowledgeProofSystem {
  
  Future<ZkProof> generateAgeProof({
    required int actualAge,
    required int minimumAge,
    required String userId,
  }) async {
    // Generate proof that age >= minimumAge without revealing actual age
    final proof = await _generateRangeProof(
      value: actualAge,
      minValue: minimumAge,
      maxValue: 150, // Reasonable maximum age
    );
    
    return ZkProof(
      proofType: ZkProofType.ageVerification,
      proof: proof,
      publicParameters: {
        'minimum_age': minimumAge,
        'statement': 'Age is at least $minimumAge years',
      },
      metadata: {
        'user_id': userId,
        'generated_at': DateTime.now().toIso8601String(),
      },
    );
  }
  
  Future<ZkProof> generateIncomeProof({
    required double actualIncome,
    required double minimumIncome,
    required String userId,
  }) async {
    final proof = await _generateRangeProof(
      value: actualIncome,
      minValue: minimumIncome,
      maxValue: 10000000, // Reasonable maximum income
    );
    
    return ZkProof(
      proofType: ZkProofType.incomeVerification,
      proof: proof,
      publicParameters: {
        'minimum_income': minimumIncome,
        'statement': 'Income is at least \$${minimumIncome.toStringAsFixed(2)}',
      },
      metadata: {
        'user_id': userId,
        'generated_at': DateTime.now().toIso8601String(),
      },
    );
  }
  
  Future<ZkProof> generateMembershipProof({
    required String actualValue,
    required List<String> allowedValues,
    required String userId,
  }) async {
    final proof = await _generateMembershipProof(actualValue, allowedValues);
    
    return ZkProof(
      proofType: ZkProofType.membershipVerification,
      proof: proof,
      publicParameters: {
        'allowed_values_hash': _hashValueList(allowedValues),
        'statement': 'Value is in the allowed set',
      },
      metadata: {
        'user_id': userId,
        'generated_at': DateTime.now().toIso8601String(),
      },
    );
  }
  
  Future<bool> verifyProof(ZkProof proof) async {
    switch (proof.proofType) {
      case ZkProofType.ageVerification:
      case ZkProofType.incomeVerification:
        return await _verifyRangeProof(proof);
      
      case ZkProofType.membershipVerification:
        return await _verifyMembershipProof(proof);
      
      default:
        return false;
    }
  }
  
  Future<Uint8List> _generateRangeProof(
    double value,
    double minValue,
    double maxValue,
  ) async {
    // Simplified range proof generation
    // In production, use proper ZK-SNARK or ZK-STARK libraries
    
    final isInRange = value >= minValue && value <= maxValue;
    if (!isInRange) {
      throw ArgumentError('Value not in specified range');
    }
    
    // Generate cryptographic proof (simplified)
    final random = Random.secure();
    final proof = Uint8List(256); // 256-byte proof
    
    for (int i = 0; i < proof.length; i++) {
      proof[i] = random.nextInt(256);
    }
    
    return proof;
  }
  
  Future<bool> _verifyRangeProof(ZkProof proof) async {
    // Simplified range proof verification
    // In production, use proper cryptographic verification
    
    return proof.proof.isNotEmpty && proof.proof.length == 256;
  }
}

// Zero-knowledge proof types
enum ZkProofType {
  ageVerification,
  incomeVerification,
  membershipVerification,
  equalityVerification,
}

// Zero-knowledge proof structure
class ZkProof {
  final ZkProofType proofType;
  final Uint8List proof;
  final Map<String, dynamic> publicParameters;
  final Map<String, dynamic> metadata;
  
  const ZkProof({
    required this.proofType,
    required this.proof,
    required this.publicParameters,
    this.metadata = const {},
  });
  
  Map<String, dynamic> toJson() {
    return {
      'proof_type': proofType.name,
      'proof': base64.encode(proof),
      'public_parameters': publicParameters,
      'metadata': metadata,
    };
  }
}

Data Minimization and Purpose Limitation

Implement data minimization and purpose limitation principles.

Data Minimization Engine

// Data minimization and purpose limitation
class DataMinimizationEngine {
  final Map<String, DataPurpose> _registeredPurposes = {};
  final Map<String, Set<String>> _purposeFieldMappings = {};
  
  void registerDataPurpose(DataPurpose purpose) {
    _registeredPurposes[purpose.id] = purpose;
    _purposeFieldMappings[purpose.id] = purpose.requiredFields.toSet();
  }
  
  Map<String, dynamic> minimizeDataForPurpose(
    Map<String, dynamic> data,
    String purposeId,
  ) {
    final purpose = _registeredPurposes[purposeId];
    if (purpose == null) {
      throw ArgumentError('Unknown purpose: $purposeId');
    }
    
    final allowedFields = _purposeFieldMappings[purposeId]!;
    final minimizedData = <String, dynamic>{};
    
    for (final field in allowedFields) {
      if (data.containsKey(field)) {
        minimizedData[field] = data[field];
      }
    }
    
    return minimizedData;
  }
  
  bool validateDataUsage(
    Map<String, dynamic> data,
    String purposeId,
    String operation,
  ) {
    final purpose = _registeredPurposes[purposeId];
    if (purpose == null) return false;
    
    // Check if operation is allowed for this purpose
    if (!purpose.allowedOperations.contains(operation)) {
      return false;
    }
    
    // Check if all used fields are allowed for this purpose
    final allowedFields = _purposeFieldMappings[purposeId]!;
    final usedFields = data.keys.toSet();
    
    return usedFields.isSubsetOf(allowedFields);
  }
  
  Future<void> auditDataUsage({
    required String userId,
    required String purposeId,
    required String operation,
    required Map<String, dynamic> data,
  }) async {
    final isValid = validateDataUsage(data, purposeId, operation);
    
    await auditLogger.logOperation(
      eventType: AuditEventType.read,
      userId: userId,
      action: 'data_usage',
      details: {
        'purpose_id': purposeId,
        'operation': operation,
        'fields_accessed': data.keys.toList(),
        'valid_usage': isValid,
      },
      success: isValid,
      severity: isValid ? AuditSeverity.info : AuditSeverity.warning,
    );
  }
}

// Data purpose definition
class DataPurpose {
  final String id;
  final String name;
  final String description;
  final List<String> requiredFields;
  final List<String> allowedOperations;
  final Duration retentionPeriod;
  final String legalBasis;
  
  const DataPurpose({
    required this.id,
    required this.name,
    required this.description,
    required this.requiredFields,
    required this.allowedOperations,
    required this.retentionPeriod,
    required this.legalBasis,
  });
}

// Example data purposes
final dataPurposes = [
  DataPurpose(
    id: 'user_authentication',
    name: 'User Authentication',
    description: 'Authenticate users and manage sessions',
    requiredFields: ['email', 'password_hash', 'last_login'],
    allowedOperations: ['read', 'update'],
    retentionPeriod: Duration(days: 365),
    legalBasis: 'contract',
  ),
  DataPurpose(
    id: 'marketing_analytics',
    name: 'Marketing Analytics',
    description: 'Analyze user behavior for marketing purposes',
    requiredFields: ['age_group', 'location', 'interests'],
    allowedOperations: ['read', 'aggregate'],
    retentionPeriod: Duration(days: 730),
    legalBasis: 'consent',
  ),
  DataPurpose(
    id: 'fraud_detection',
    name: 'Fraud Detection',
    description: 'Detect and prevent fraudulent activities',
    requiredFields: ['transaction_history', 'device_info', 'ip_address'],
    allowedOperations: ['read', 'analyze'],
    retentionPeriod: Duration(days: 2555), // 7 years
    legalBasis: 'legitimate_interests',
  ),
];

Compliance Monitoring and Reporting

Automated compliance monitoring and reporting system.

Compliance Dashboard

// Comprehensive compliance monitoring
class ComplianceMonitor {
  final List<ComplianceFramework> frameworks;
  final AuditLogger auditLogger;
  
  ComplianceMonitor({
    required this.frameworks,
    required this.auditLogger,
  });
  
  Future<ComplianceReport> generateComplianceReport({
    DateTime? startDate,
    DateTime? endDate,
    List<String>? frameworkIds,
  }) async {
    final start = startDate ?? DateTime.now().subtract(Duration(days: 30));
    final end = endDate ?? DateTime.now();
    
    final frameworkReports = <String, FrameworkComplianceReport>{};
    
    for (final framework in frameworks) {
      if (frameworkIds != null && !frameworkIds.contains(framework.id)) {
        continue;
      }
      
      frameworkReports[framework.id] = await _generateFrameworkReport(
        framework,
        start,
        end,
      );
    }
    
    return ComplianceReport(
      reportId: _generateReportId(),
      generatedAt: DateTime.now(),
      periodStart: start,
      periodEnd: end,
      frameworkReports: frameworkReports,
      overallScore: _calculateOverallScore(frameworkReports),
    );
  }
  
  Future<FrameworkComplianceReport> _generateFrameworkReport(
    ComplianceFramework framework,
    DateTime start,
    DateTime end,
  ) async {
    final controlResults = <String, ControlResult>{};
    
    for (final control in framework.controls) {
      controlResults[control.id] = await _evaluateControl(control, start, end);
    }
    
    return FrameworkComplianceReport(
      frameworkId: framework.id,
      frameworkName: framework.name,
      controlResults: controlResults,
      complianceScore: _calculateFrameworkScore(controlResults),
      recommendations: _generateRecommendations(controlResults),
    );
  }
  
  Future<ControlResult> _evaluateControl(
    ComplianceControl control,
    DateTime start,
    DateTime end,
  ) async {
    switch (control.type) {
      case ControlType.auditLog:
        return await _evaluateAuditLogControl(control, start, end);
      
      case ControlType.accessControl:
        return await _evaluateAccessControl(control, start, end);
      
      case ControlType.dataProtection:
        return await _evaluateDataProtectionControl(control, start, end);
      
      case ControlType.changeManagement:
        return await _evaluateChangeManagementControl(control, start, end);
      
      default:
        return ControlResult(
          controlId: control.id,
          status: ControlStatus.notApplicable,
          score: 0.0,
          findings: ['Control type not implemented'],
        );
    }
  }
  
  Future<List<ComplianceAlert>> monitorRealTimeCompliance() async {
    final alerts = <ComplianceAlert>[];
    
    // Monitor for compliance violations
    final recentLogs = await auditLogger.queryLogs(
      startTime: DateTime.now().subtract(Duration(hours: 1)),
      limit: 1000,
    );
    
    // Check for excessive failed login attempts
    final failedLogins = recentLogs
        .where((log) => log.eventType == AuditEventType.login && !log.success)
        .length;
    
    if (failedLogins > 50) {
      alerts.add(ComplianceAlert(
        severity: AlertSeverity.high,
        framework: 'GDPR',
        control: 'Access Control',
        message: 'Excessive failed login attempts detected',
        details: {'failed_attempts': failedLogins},
        detectedAt: DateTime.now(),
      ));
    }
    
    // Check for unauthorized data access
    final unauthorizedAccess = recentLogs
        .where((log) => log.eventType == AuditEventType.permissionDenied)
        .length;
    
    if (unauthorizedAccess > 20) {
      alerts.add(ComplianceAlert(
        severity: AlertSeverity.medium,
        framework: 'HIPAA',
        control: 'Minimum Necessary',
        message: 'High number of unauthorized access attempts',
        details: {'unauthorized_attempts': unauthorizedAccess},
        detectedAt: DateTime.now(),
      ));
    }
    
    return alerts;
  }
}

Summary

Vektagraf's privacy-preserving features and compliance tools provide:

• Comprehensive Regulatory Compliance with GDPR, HIPAA, and SOX support
• Advanced Privacy Technologies including differential privacy and zero-knowledge proofs
• Data Minimization and Purpose Limitation for privacy by design
• Automated Compliance Monitoring with real-time alerts and reporting
• Privacy-Preserving Analytics for secure data insights
• Consent Management with granular control and audit trails

Key Takeaways

1. Privacy by Design: Build privacy protection into the system architecture
2. Regulatory Compliance: Implement comprehensive frameworks for multiple regulations
3. Advanced Cryptography: Use differential privacy and zero-knowledge proofs for enhanced protection
4. Data Governance: Implement data minimization and purpose limitation principles
5. Continuous Monitoring: Use automated compliance monitoring and alerting

Next Steps

• Chapter 11: Learn about multi-tenant security architecture
• Chapter 12: Explore transport layer integration and security
• Chapter 13: Understand monitoring and observability for compliance

Related Resources

• GDPR Official Text
• HIPAA Security Rule
• SOX Compliance Guide
• Differential Privacy Resources
• Zero-Knowledge Proofs Explained