Google's Chrome team has launched a new initiative to protect HTTPS connections from the future threat of quantum computers. The effort focuses on redesigning how digital certificates work so they can withstand quantum-powered attacks without slowing down the web.

The move follows the formation of a new working group at the Internet Engineering Task Force (IETF) called PLANTS, short for PKI, Logs and Tree Signatures.

The group is addressing technical hurdles linked to quantum-resistant cryptography, which typically increases the size of data exchanged during TLS connections. Larger certificates can create performance and bandwidth challenges, particularly for systems relying on Certificate Transparency logs.

Why Chrome Is Moving Beyond Traditional Certificates

Rather than adding larger post-quantum X.509 certificates to its existing root store, Chrome is collaborating with industry partners to develop Merkle Tree Certificates (MTCs). These certificates are being standardized within the PLANTS working group.

MTCs replace the traditional chain of digital signatures with compact proof derived from a Merkle tree structure.

Instead of signing each certificate individually, a Certification Authority signs a single "Tree Head" that can represent millions of certificates. Browsers then receive a lightweight proof confirming a site's inclusion in that tree.

The approach is designed to reduce the amount of authentication data transmitted during a TLS handshake. It also embeds transparency directly into the certificate issuance process, removing the need for separate Certificate Transparency checks.

Read more on quantum-resistant cryptography: Quantum Computers Are Coming for Your Crypto Keys, But Not Yet

Three-Phase Rollout Underway

Chrome has already begun testing MTCs on live internet traffic and outlined a three-stage deployment plan:

• Phase 1, currently underway, includes a feasibility study with Cloudflare, with every MTC-backed connection paired with a traditional X.509 certificate as a fail-safe

• Phase 2, scheduled for the first quarter of 2027, will invite selected Certificate Transparency log operators to help bootstrap public MTC deployment

• Phase 3, planned for the third quarter of 2027, will introduce the Chrome Quantum-resistant Root Store, a new trust framework dedicated solely to MTCs

The new root programme will operate alongside Chrome's existing root store to ensure continuity and stability during the transition.

Beyond the technical framework, Chrome says it is using the transition to modernize certificate governance. Proposed updates include ACME-only workflows, streamlined revocation systems and enhanced oversight models designed for continuous, externally verifiable monitoring.

The team also confirmed it will continue supporting existing certificate authorities within the current Chrome Root Store, while building infrastructure for quantum-resistant HTTPS. Traditional X.509 certificates using quantum-safe algorithms may still be supported in private PKIs later this year.

"As we execute and refine our work on MTCs, we look forward to sharing a concrete policy framework for a quantum-resistant root store with the community, and are excited to learn and define clear pathways for organizations to operate as Chrome-trusted MTC CAs," the Chrome team concluded.