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TLS Encrypted ClientHello: ECH RFC 9849 and DNS deployment guide

A technical guide to Encrypted ClientHello, ECHConfig publication, HTTPS DNS records, key rotation and privacy limitations.

IRIROSG Editorial·2026-11-09·1 min read·75 body words

TLS Encrypted ClientHello: ECH RFC 9849 and DNS deployment guide

RFC 9849 standardizes TLS Encrypted ClientHello, helping protect sensitive ClientHello details such as the requested server name. The guide explains the inner and outer handshake, ECHConfig, DNS HTTPS/SVCB records and operational considerations for CDN deployments, browsers and certificates. It also clarifies that ECH does not hide destination IP addresses or guarantee complete anonymity. The complete technical article is available in Persian.

This is an English overview. The complete original article is currently published in Persian.

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Sources & further reading

IETF RFC 9849 — TLS Encrypted Client Hellohttps://www.rfc-editor.org/rfc/rfc9849.html

IETF RFC 9460 — DNS HTTPS and SVCB recordshttps://www.rfc-editor.org/rfc/rfc9460.html

Cloudflare technical explanation of encrypted ClientHellohttps://blog.cloudflare.com/encrypted-client-hello/

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