DNSSEC’s post-quantum signatures challenge ordinary packet sizes

Cloudflare’s 1.1.1.1 resolver now validates DNSSEC signatures using ML-DSA-44. Each signature is 2,420 bytes, already larger than common DNS-over-UDP limits before the rest of the response is added. The engineering challenge includes transporting larger answers reliably and preventing compatibility with older signature algorithms from becoming a way to downgrade protection.

Cloudflare · Sep 10, 2026

Why it matters

Cryptography migrations can expose networking assumptions long before the underlying mathematics becomes the bottleneck.

More context

Read the September 10 explanation and its test-domain example. Existing 1.1.1.1 users need no setting change; validation applies when a zone publishes the necessary records. Test TCP fallback in environments you operate.

Keep in mind

This announcement covers resolver validation. Authoritative signing and registrar support were described as future work, so it does not mean every DNS lookup is now protected end to end.

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