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Cloudflare deployed Automatic Key Exchange for TLS connections between its edge network and customer origins, replacing a universal X25519 key-agreement assumption with per-origin measurements of supported and preferred key-exchange groups. The system probes origins outside production traffic, refreshes results daily, and gradually applies learned settings with rollback controls when connection failures or retry rates increase.
For scanned origins, the change reduced TLS HelloRetryRequest rates from roughly 52% to 3.7% and cut more than 150 ms from p90 handshake latency. It also enables most compatible X25519MLKEM768 post-quantum hybrid handshakes to complete in one round trip, although legacy origins may reject the larger ClientHello key share and strict TLS compliance policies can prevent TLS 1.3 connections where no mutually permitted algorithm exists.
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Cloudflare began supporting ML-DSA post-quantum signatures in Authenticated Origin Pulls and Custom Origin Trust Store in mid-2026.
Since September 2023, Cloudflare has led origin TLS handshakes with classical X25519 and used HelloRetryRequest as a safety mechanism for post-quantum upgrades, requiring capable post-quantum origins to complete a second round trip.
Cloudflare retained the Origin Post-Quantum Encryption API, but it no longer changes a zone's post-quantum key-agreement behavior.
Cloudflare introduced Compliance requirements settings that can limit origin TLS negotiations to post-quantum hybrid algorithms, FIPS-compliant algorithms, or compatible combinations. Enforcing requirements where no mutually supported algorithm exists can cause TLS 1.3 connections to fail.
Automatic Key Exchange selects X25519MLKEM768 where supported, allowing most compatible post-quantum origin handshakes to complete in one round trip. Among scanned origins, 33% moved to the hybrid exchange and the share of scanned post-quantum TLS 1.3 traffic completing without HelloRetryRequest rose from 0% to 99.2%.
Cloudflare introduced Automatic Key Exchange, which actively probes origins for supported and preferred TLS key-agreement groups and gradually deploys learned zone-level preferences with rollback protections. The system reduced HelloRetryRequests among scanned origins from roughly 52% to 3.7% and removed more than 150 ms from p90 origin-handshake latency.
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IETF RFC `10024` establishes three hybrid post-quantum TLS 1.3 key-agreement groups that combine ML-KEM with elliptic-curve Diffie-Hellman. `X25519MLKEM768` is the only group designated **Recommended** in IANA’s TLS Supported Groups registry; NIST-curve variants remain available for compliance-focused deployments. The standard formalizes an approach already used by browsers, CDNs, and TLS libraries and discourages use of earlier Kyber768 draft code points, reducing a standards barrier to mitigating harvest-now-decrypt-later exposure. Cloudflare has deployed Automatic Key Exchange to probe origin-server capabilities and select the strongest mutually supported TLS 1.3 group, prioritizing `X25519MLKEM768`. The rollout increased post-quantum traffic across scanned origins from roughly 25 billion to 45 billion daily connections, with 99.2% of post-quantum handshakes completing in one network round trip; retry-dependent handshakes fell from about 52% to 3.7%, cutting 90th-percentile handshake latency by more than 150 ms. Organizations still need origins that support `X25519MLKEM768` to receive end-to-end hybrid key-establishment protection, while post-quantum TLS authentication remains constrained by limited public WebPKI support for ML-DSA certificates and trusted roots.
Sep 13, 2026
Cloudflare has added post-quantum authentication to **Authenticated Origin Pulls** and **Custom Origin Trust Store**, enabling customers to use **ML-DSA** signatures for Cloudflare-to-origin TLS and build fully post-quantum-secure mutual TLS on that link. The company said the protection is effective only if organizations also remove trust in classical authentication paths to avoid downgrade attacks, and positioned the release as a key step toward its stated goal of full post-quantum security by 2029. Cloudflare also noted that post-quantum authentication for browser-facing WebPKI traffic will follow a different approach based on **Merkle Tree Certificates**. The rollout comes amid broader industry acceleration toward quantum-safe security. Cloudflare Radar has been tracking worldwide post-quantum encryption adoption, while Microsoft said the timeline for quantum risk is shifting and urged faster migration planning. Cloudflare said the new capability required changes across its Go-based control plane and **Pingora Origin** data plane, and disclosed that a **BoringSSL** upgrade triggered a June 10, 2026 incident when stricter `KeyUsage` enforcement caused compatibility problems before the issue was patched and resolved.
Jul 29, 2026
Let's Encrypt said it will use **Merkle Tree Certificates (MTCs)** as its preferred approach for post-quantum authentication on the public web, arguing that conventional post-quantum signatures such as `ML-DSA` would make standard TLS certificate chains too large for reliable internet-scale handshakes. The model batches certificate issuance under a single signed Merkle tree head and delivers compact inclusion proofs, reducing handshake overhead while making Certificate Transparency inherent to issuance. Let’s Encrypt said current subscribers do not need to take immediate action, but future ACME clients and related tooling will need updates as the ecosystem moves toward the new format. The move aligns Let’s Encrypt with broader work by **Google, Cloudflare, Chrome, DigiCert, and the IETF**, as browser and infrastructure vendors push for scalable post-quantum TLS ahead of government migration deadlines from the NSA, NIST, and the EU. Let’s Encrypt plans a staging environment for MTC issuance in late 2026 and a production-ready deployment in 2027, while continuing to track `ML-DSA` support for traditional X.509 use cases outside the browser ecosystem. It also said the more urgent near-term defense remains post-quantum encryption against harvest-now-decrypt-later threats, urging operators to enable hybrid key exchange such as: ```text X25519MLKEM768 ```
Jun 29, 2026