HPKE: Standardizing public-key encryption (finally!)

This post introduces Hybrid Public Key Encryption (HPKE) as RFC 9180, a new standard for public-key encryption designed for simplicity, reusability, and future-proofing. It details the motivation, design goals (algorithm agility, authentication modes), and construction of HPKE, highlighting its use in emerging privacy-focused internet standards like Encrypted Client Hello and Oblivious DNS-over-HTTPS, and its implementation in Cloudflare's CIRCL library. This contributes to Cloudflare's broader efforts in privacy-enhancing technologies.