Privacy by Design is a legal obligation. But what technologies actually make it work at a technical level?

Privacy by Design rests on three technical pillars: anonymity technologies, privacy-preserving computations, and privacy policy enforcement.

* Tor onion routing, an anonymity PET. — Tga.D, CC BY-SA 4.0, via Wikimedia Commons. *

Anonymity technologies:

• TOR for anonymous browsing through onion routing.
• Zero-knowledge proofs, where you prove something is true without revealing the underlying data. For example, proving you're over 18 without revealing your birth date.
• k-anonymity, ensuring each record in a dataset is indistinguishable from at least k minus 1 other records.
• l-diversity, extending k-anonymity by requiring that sensitive attributes have diverse values within each group, preventing inference attacks.

Privacy-preserving computations:

• Searching over encrypted data without decrypting it first.
• Homomorphic encryption, performing calculations on encrypted data and getting encrypted results. The server never sees the plaintext.
• Secure multi-party computation, where multiple parties jointly compute a result without any party revealing their individual input.

Privacy policy enforcement:

• Private Information Retrieval, querying a database without the server knowing what you asked for.
• Differential privacy, adding mathematical noise to protect individuals in aggregate datasets.
• Policy-based access control systems that automatically enforce data handling rules.

Go deeper:

• k-anonymity (Wikipedia) — the indistinguishable-records model, with l-diversity context.
• Homomorphic encryption (Wikipedia) — computing on ciphertext without decrypting.
• ENISA — Data Protection Engineering — practical guidance mapping PETs to principles.