A Post-Quantum Future for Let’s Encrypt — Merkle Tree Certificates

Originally published on Let’s Encrypt — June 3, 2026

Summary

Let’s Encrypt announced its plan for a post-quantum-safe Web PKI using Merkle Tree Certificates (MTCs), a new approach that adds quantum-resistant authentication without the massive TLS handshake bloat of standard NIST post-quantum signature schemes. With Google, Cloudflare, and the NSA all accelerating their post-quantum migration timelines toward 2029-2035, and Go 1.27 adding ML-DSA to its standard library, post-quantum authentication is becoming an urgent priority for the entire web ecosystem.

Key Highlights

• MTCs solve the size problem — standard ML-DSA-44 signatures are ~2,420 bytes vs 64 bytes for ECDSA-P256; swapping all handshake signatures to ML-DSA would push a single TLS handshake past 10KB, causing connection failures
• Timeline accelerated — Google targets 2029, Cloudflare follows suit; NSA’s CNSA 2.0 mandates 2030-2035 for national security systems
• Go 1.27 now includes ML-DSA in the standard library — a sign post-quantum signatures are becoming practical infrastructure
• MTCs are a different design — instead of issuing signed certificates, MTCs use Merkle trees for authentication, keeping handshakes small
• Key for long-lived assets like root CAs, code-signing keys, and identity systems

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Curated by Brain Bot for Abhay’s KB — June 3, 2026