Google on Friday outlined a plan for Chrome to secure HTTPS certificates against quantum computer attacks without breaking the Internet. The core challenge is that quantum-resistant cryptographic data needed to publish TLS certificates at scale would be roughly 40 times larger than today’s material, which could slow handshakes and leave some users behind.
To address this, Google and partners are turning to Merkle Tree Certificates. In this model, a Certification Authority signs a single “Tree Head” that could cover millions of certificates, and the certificate sent to a browser is a lightweight proof of inclusion in that tree rather than a full serialized chain.
Cloudflare is working with Google on the approach, highlighting concerns that bigger certificates could slow connections and complicate middleboxes that sit between clients and sites. The Merkle scheme is intended to keep security intact while reducing the amount of data that must be transmitted during TLS handshakes.
Chrome already supports Merkle Tree Certificate concepts, and broader adoption would require collaboration among certificate authorities, transparency logs, and PKI standards bodies. In this vein, an IETF working group on PKI, Logs, and Tree Signatures is coordinating ongoing standards development.
Google frames Merkle Tree Certificates as a practical path toward quantum-resilient web security. The approach combines post-quantum cryptographic proofs with traditional certificates, enabling verification of certificate presence without flooding the network with full chain data. The project underscores the challenge of maintaining performance while strengthening resilience against quantum threats.
