Handshake Encryption: Endgame (an ECH update)

What this post added

This post details the initial deployment of TLS Encrypted Client Hello (ECH), an extension to TLS that encrypts sensitive metadata in the ClientHello message. It explains the privacy benefits of ECH by preventing the visibility of target server names to network observers, contrasting it with DNS-over-HTTPS (DoH). The post also delves into the evolving threat model for ECH, discussing active and passive attacks and how ECH's design aims to mitigate them, particularly concerning the anonymity set and preventing domain fronting.