privacy-by-design

# Privacy by Design ## Overview Integrate privacy protections into software architecture from the beginning, not as an afterthought. This skill applies Privacy by Design principles (GDPR Article 25, Cavoukian's framework) when designing databases, APIs, and user flows. Protects real users' data and builds trust. ## When to Use This Skill - Use when building apps that collect personal data (names, emails, locations, preferences) - Use when designing database schemas, APIs, or authentication flows - Use when the user mentions forms, user accounts, analytics, or third-party integrations - Use when deploying to production—verify privacy controls before launch ## Legal Frameworks **GDPR (EU)** — Primary reference. Article 25 mandates "data protection by design and by default." Applies to EU users and often adopted globally. **CCPA (California)** — Right to know, delete, opt-out of sale. Similar principles: minimize, disclose, allow control. **LGPD (Brazil)** — Aligned with GDPR. Purpose limitation, necessity, transparency. Applies to Brazil users. Design for the strictest framework you target; it often satisfies others. --- ## Core Principles ### 1. Data Minimization Collect only what is strictly necessary. Every field needs a documented justification. Avoid "we might need it later." ### 2. Purpose Limitation Store the purpose of each data point. Do not reuse data for purposes the user did not consent to. ### 3. Storage Limitation Define retention periods. Implement ...