1.1.1.1 now supports post-quantum DNSSEC, all 2,420 bytes of it

1.1.1.1 now validates DNSSEC signatures made with ML-DSA-44, a post-quantum signature algorithm standardized by the National Institute of Standards and Technology (NIST). This is a first step toward preparing DNSSEC for a future in which today’s signature algorithms are no longer secure.

Cloudflare plans to achieve full post-quantum security by 2029. Much of the work so far has focused on TLS, but public-key cryptography is used in many other systems, including DNSSEC.

While we began experimenting with post-quantum key agreement in TLS in 2019 and enabled support for all customers in 2022, post-quantum signatures have not yet received comparable testing in DNSSEC. There is also some urgency. Widespread client adoption of post-quantum TLS took years, partly because larger messages exposed assumptions and bugs in existing network software. That experience showed why early large-scale testing matters. We cannot wait until quantum computers become an immediate threat.

The problem is that post-quantum signatures are large. Each ML-DSA-44 signature is 2,420 bytes, exceeding common DNS-over-UDP limits before the response includes anything else. At the same time, zones will need to publish conventional signatures for older resolvers for years, creating a potential downgrade path if not validated correctly. The challenge is carrying these much larger responses reliably, without allowing compatibility with older resolvers to weaken protection for newer ones.

With ML-DSA-44 validation enabled, 1.1.1.1 lets us test both challenges at Internet scale: carrying larger DNS responses and preventing fallback to conventional signatures.

Why post-quantum DNSSEC matters