Keeping the Internet fast and secure: introducing Merkle Tree Certificates

Cloudflare’s post argues that Merkle Tree Certificates (MTCs) are a proposed next generation of the WebPKI designed to reduce the number of signatures and public keys in the TLS handshake, while retaining security properties. It explains that current TLS handshakes involve multiple signatures and keys, totalling five signatures and two public keys, and that MTCs achieve a significantly smaller footprint by using a Merkle tree inclusion proof in place of per-certificate signatures.

The certificate example shown is a batch-issued, signatureless certificate with an inclusion proof, issued by a Merkle Tree Certification Authority (MTCA) in batches, and the system relies on signed treeheads disseminated out-of-band.

The article notes experimental deployment planned with Chrome, a bootstrap certificate approach to bootstrap trust, and that roughly half of Cloudflare’s traffic is already protected by post-quantum encryption, with the aim of enabling a default, low-overhead post-quantum solution today. According to IETF, the plan is to deploy MTCs on an experimental basis and study their impact on protocol ossification, performance, and client update rates.