ACCORDING to the Chrome Secure Web and Networking Team, Google is developing an evolution of HTTPS certificates based on Merkle Tree Certificates (MTCs) to help secure the web against future quantum risks, while avoiding traditional X.509 certificates in the Chrome Root Store for now.
The approach, currently in development in the PLANTS working group, would use a single Certification Authority to sign a Tree Head representing potentially millions of certificates, with the browser receiving a lightweight proof of inclusion in that tree. Google says MTCs would shrink authentication data in a TLS handshake, helping post-quantum security without increasing bandwidth, thereby keeping performance comparable to today’s internet.
Phase 1 is in progress as a feasibility study with Cloudflare to evaluate TLS connections relying on MTCs; Phase 2 targets Q1 2027 and involves inviting Certificate Transparency log operators with usable logs in Chrome before 1 February 2026 to bootstraps public MTCs. Phase 3, planned for Q3 2027, will finalise onboarding requirements for additional CAs into the Chrome Quantum-resistant Root Store and its Root Program that only supports MTCs.