Google Develops Merkle Tree Certificates to Enable Quantum-Resistant HTTPS in Chrome

Google will adopt Merkle Tree Certificates (MTCs) in Chrome to make HTTPS certificates resilient against future quantum attacks while avoiding bulky post-quantum X.509 chains. The company is collaborating with Cloudflare and the PLANTS working group to test MTCs and will roll out a phased program culminating in a Chrome Quantum-resistant Root Store (CQRS) by Q3 2027. #MerkleTreeCertificates #Chrome

Keypoints

Google will not add traditional X.509 post-quantum certificates to the Chrome Root Store and is pursuing MTCs instead.
MTCs allow a CA to sign a single Tree Head while browsers receive lightweight proofs of inclusion for individual certificates.
The MTC model minimizes TLS handshake bandwidth and decouples cryptographic algorithm strength from transmitted data size.
Google and Cloudflare are running a feasibility study now and plan phased expansion with CT Log involvement in early 2027.
By Q3 2027 Google aims to establish a Chrome Quantum-resistant Root Store (CQRS) and a Root Program that supports only MTCs.