GOOGLE is pursuing quantum-safe HTTPS for Chrome by evolving certificates to Merkle Tree Certificates (MTCs). According to Google, the Chrome Root Store will not immediately accept post-quantum certificates because of potential impacts on TLS performance and CT-related bandwidth. Instead, Chrome will move to MTC-based certificates, where a CA signs a single “Tree Head” and the certificate delivered to the browser is a lightweight proof of inclusion in that tree.
MTCs reduce the authentication data in the TLS handshake, decouple data size from algorithm strength, and aim to keep the post-quantum web fast while boosting security. Google has been testing MTCs in Chrome and has partnered with Cloudflare to assess performance and security, with CT Log operators invited to participate in bootstrapping public MTCs in the first quarter of 2027, after core technology validation.
By the third quarter of 2027, Google expects to finalise onboarding requirements for CAs into a new Chrome Quantum-resistant Root Store and the MTCs-only Root Program, establishing a dedicated trust store for a post-quantum web.