Cloudflare to become a public certificate authority with post-quantum certificates

Cloudflare Inc. today announced plans to become a public certificate authority that will offer certificates designed for the point when quantum computers can break current encryption. The new authority will issue a post-quantum format called Merkle Tree Certificates from the same system as conventional ones.

The format is aimed at a size problem in post-quantum certificates. Output from one of the newly standardized post-quantum signature algorithms runs to 2,420 bytes, against 64 bytes for the elliptic curve schemes most sites use now. A typical connection carries several. Cloudflare expects quantum computers capable of breaking today’s encryption within years.

Merkle Tree Certificates, which Cloudflare co-authored as an Internet Engineering Task Force draft specification, avoid sending large signatures with every connection. A lightweight proof that the certificate sits in a trusted public log does the verification work.

Cloudflare said a joint experiment with Google LLC’s Chrome team, announced last October, was successful. Let’s Encrypt, the nonprofit issuer, said in June that it expects to issue the format in production in 2027.

Running its own authority is also a break from how Cloudflare has handled certificates until now. Its developer documentation names three outside issuers, Let’s Encrypt among them, as the authorities signing certificates for Cloudflare’s free Universal SSL program. A small group of dominant providers handles most certificate issuance on the web. Cloudflare called that concentration a systemic risk if any one of them fails or is compromised.