Cloudflare is developing a public certificate authority for Merkle Tree Certificates, an approach designed to reduce the bandwidth cost of securing the web against future quantum attacks. The company is targeting evaluation for Chrome’s quantum-resistant Root Store in early 2027.
Traditional certificate chains could become much larger when they adopt post-quantum signatures. Cloudflare says those signatures can be roughly 40 times the size of classical ones. Merkle Tree Certificates instead place certificate data in an append-only tree, sign a checkpoint and let a browser verify a compact proof that a certificate is included.
A Chrome experiment delivered billions of these certificates to half of Chrome Beta 146 users for selected Cloudflare domains. Cloudflare reported 9% faster median performance, largely because intermediate certificates were removed. The test used classical signatures, however, so it did not measure the full post-quantum configuration.
The design adds independent log cosigners to detect inconsistent records, while servers retain a standalone certificate for clients missing the latest tree landmark. Important questions remain around revocation, incident response, interoperability and availability at production scale. Wider use also depends on browser support and a diverse ecosystem of certificate authorities and independent monitors, not just Cloudflare’s implementation.