Cloudflare 1.1.1.1 Begins Supporting Post-Quantum DNSSEC Signature Verification with 2,420-byte Signatures

Cloudflare's 1.1.1.1 DNS resolver has begun supporting DNSSEC signature verification for the NIST-standardized post-quantum signature algorithm ML-DSA-44. This is part of Cloudflare's plan to achieve full post-quantum security by 2029, aimed at conducting early large-scale testing to prepare for quantum computing threats.

Increased Signature Size and Network Challenges

ML-DSA-44 signatures are 2,420 bytes, approximately 38 times larger than existing ECDSA P-256 signatures (64 bytes). This exceeds the typical DNS-over-UDP message size limit, requiring TCP retries instead of fragmentation. According to Cloudflare statistics, approximately 85% of all queries arrive via UDP, so this change significantly impacts network processing methods.

Preventing Downgrade Attacks and Verification Policy

While parallel issuance is necessary for compatibility with existing algorithms, the 'single valid path' allowance rule in RFC 6840 creates a risk that attackers could bypass verification through vulnerable existing algorithms. To prevent this, 1.1.1.1 requires at least one valid post-quantum verification path and applies an enhanced local policy that treats the entire verification as failed if the ML-DSA-44 path verification fails.

Need for Ecosystem-Wide Migration

DNSSEC migration does not end with resolver support alone. A continuous Chain of Trust must be established where Authoritative servers, Registrars, Registries, and the Root zone adopt and protect ML-DSA-44. Cloudflare plans to provide free support for ML-DSA-44 signatures and DS records in Authoritative DNS and Registrar services in the future.