gdpr-data-handling

GDPR Data Handling

Practical implementation guide for GDPR-compliant data processing, consent management, and privacy controls.

When to Use This Skill

• Building systems that process EU personal data
• Implementing consent management
• Handling data subject requests (DSRs)
• Conducting GDPR compliance reviews
• Designing privacy-first architectures
• Creating data processing agreements

Core Concepts

1. Personal Data Categories

| Category | Examples | Protection Level | |----------|----------|------------------| | Basic | Name, email, phone | Standard | | Sensitive (Art. 9) | Health, religion, ethnicity | Explicit consent | | Criminal (Art. 10) | Convictions, offenses | Official authority | | Children's | Under 16 data | Parental consent |

2. Legal Bases for Processing

Article 6 - Lawful Bases:
├── Consent: Freely given, specific, informed
├── Contract: Necessary for contract performance
├── Legal Obligation: Required by law
├── Vital Interests: Protecting someone's life
├── Public Interest: Official functions
└── Legitimate Interest: Balanced against rights

3. Data Subject Rights

Right to Access (Art. 15)      ─┐
Right to Rectification (Art. 16) │
Right to Erasure (Art. 17)       │ Must respond
Right to Restrict (Art. 18)      │ within 1 month
Right to Portability (Art. 20)   │
Right to Object (Art. 21)       ─┘

Implementation Patterns

Pattern 1: Consent Management

// Consent data model
const consentSchema = {
  userId: String,
  consents: [{
    purpose: String,         // 'marketing', 'analytics', etc.
    granted: Boolean,
    timestamp: Date,
    source: String,          // 'web_form', 'api', etc.
    version: String,         // Privacy policy version
    ipAddress: String,       // For proof
    userAgent: String        // For proof
  }],
  auditLog: [{
    action: String,          // 'granted', 'withdrawn', 'updated'
    purpose: String,
    timestamp: Date,
    source: String
  }]
};

// Consent service
class ConsentManager {
  async recordConsent(userId, purpose, granted, metadata) {
    const consent = {
      purpose,
      granted,
      timestamp: new Date(),
      source: metadata.source,
      version: await this.getCurrentPolicyVersion(),
      ipAddress: metadata.ipAddress,
      userAgent: metadata.userAgent
    };

    // Store consent
    await this.db.consents.updateOne(
      { userId },
      {
        $push: {
          consents: consent,
          auditLog: {
            action: granted ? 'granted' : 'withdrawn',
            purpose,
            timestamp: consent.timestamp,
            source: metadata.source
          }
        }
      },
      { upsert: true }
    );

    // Emit event for downstream systems
    await this.eventBus.emit('consent.changed', {
      userId,
      purpose,
      granted,
      timestamp: consent.timestamp
    });
  }

  async hasConsent(userId, purpose) {
    const record = await this.db.consents.findOne({ userId });
    if (!record) return false;

    const latestConsent = record.consents
      .filter(c => c.purpose === purpose)
      .sort((a, b) => b.timestamp - a.timestamp)[0];

    return latestConsent?.granted === true;
  }

  async getConsentHistory(userId) {
    const record = await this.db.consents.findOne({ userId });
    return record?.auditLog || [];
  }
}

<!-- GDPR-compliant consent UI -->
<div class="consent-banner" role="dialog" aria-labelledby="consent-title">
  <h2 id="consent-title">Cookie Preferences</h2>

  <p>We use cookies to improve your experience. Select your preferences below.</p>

  <form id="consent-form">
    <!-- Necessary - always on, no consent needed -->
    <div class="consent-category">
      <input type="checkbox" id="necessary" checked disabled>
      <label for="necessary">
        <strong>Necessary</strong>
        <span>Required for the website to function. Cannot be disabled.</span>
      </label>
    </div>

    <!-- Analytics - requires consent -->
    <div class="consent-category">
      <input type="checkbox" id="analytics" name="analytics">
      <label for="analytics">
        <strong>Analytics</strong>
        <span>Help us understand how you use our site.</span>
      </label>
    </div>

    <!-- Marketing - requires consent -->
    <div class="consent-category">
      <input type="checkbox" id="marketing" name="marketing">
      <label for="marketing">
        <strong>Marketing</strong>
        <span>Personalized ads based on your interests.</span>
      </label>
    </div>

    <div class="consent-actions">
      <button type="button" id="accept-all">Accept All</button>
      <button type="button" id="reject-all">Reject All</button>
      <button type="submit">Save Preferences</button>
    </div>

    <p class="consent-links">
      <a href="/privacy-policy">Privacy Policy</a> |
      <a href="/cookie-policy">Cookie Policy</a>
    </p>
  </form>
</div>

Pattern 2: Data Subject Access Request (DSAR)

from datetime import datetime, timedelta
from typing import Dict, List, Optional
import json

class DSARHandler:
    """Handle Data Subject Access Requests."""

    RESPONSE_DEADLINE_DAYS = 30
    EXTENSION_ALLOWED_DAYS = 60  # For complex requests

    def __init__(self, data_sources: List['DataSource']):
        self.data_sources = data_sources

    async def submit_request(
        self,
        request_type: str,  # 'access', 'erasure', 'rectification', 'portability'
        user_id: str,
        verified: bool,
        details: Optional[Dict] = None
    ) -> str:
        """Submit a new DSAR."""
        request = {
            'id': self.generate_request_id(),
            'type': request_type,
            'user_id': user_id,
            'status': 'pending_verification' if not verified else 'processing',
            'submitted_at': datetime.utcnow(),
            'deadline': datetime.utcnow() + timedelta(days=self.RESPONSE_DEADLINE_DAYS),
            'details': details or {},
            'audit_log': [{
                'action': 'submitted',
                'timestamp': datetime.utcnow(),
                'details': 'Request received'
            }]
        }

        await self.db.dsar_requests.insert_one(request)
        await self.notify_dpo(request)

        return request['id']

    async def process_access_request(self, request_id: str) -> Dict:
        """Process a data access request."""
        request = await self.get_request(request_id)

        if request['type'] != 'access':
            raise ValueError("Not an access request")

        # Collect data from all sources
        user_data = {}
        for source in self.data_sources:
            try:
                data = await source.get_user_data(request['user_id'])
                user_data[source.name] = data
            except Exception as e:
                user_data[source.name] = {'error': str(e)}

        # Format response
        response = {
            'request_id': request_id,
            'generated_at': datetime.utcnow().isoformat(),
            'data_categories': list(user_data.keys()),
            'data': user_data,
            'retention_info': await self.get_retention_info(),
            'processing_purposes': await self.get_processing_purposes(),
            'third_party_recipients': await self.get_recipients()
        }

        # Update request status
        await self.update_request(request_id, 'completed', response)

        return response

    async def process_erasure_request(self, request_id: str) -> Dict:
        """Process a right to erasure request."""
        request = await self.get_request(request_id)

        if request['type'] != 'erasure':
            raise ValueError("Not an erasure request")

        results = {}
        exceptions = []

        for source in self.data_sources:
            try:
                # Check for legal exceptions
                can_delete, reason = await source.can_delete(request['user_id'])