Cloudflare has added support for validating post-quantum DNSSEC signatures on its 1.1.1.1 public DNS resolver, marking an early step toward protecting the domain name system from future quantum-computing attacks.
The company is now validating signatures created with ML-DSA-44, a post-quantum algorithm standardized by the US National Institute of Standards and Technology (NIST).
Cloudflare engineers report this change will let the company test post-quantum DNSSEC at Internet scale before quantum computers can break today’s public-key cryptography.
DNSSEC is designed to prevent attackers from forging DNS responses and redirecting users to malicious destinations. A validating resolver such as 1.1.1.1 checks a chain of cryptographic signatures between the DNS root and the requested domain to confirm that DNS records have not been altered.
Cloudflare operates one of the world’s largest Internet infrastructure networks and provides services including DNS, content delivery, security, and connectivity products. Its 1.1.1.1 service is a widely used public DNS resolver, making it a useful platform for testing changes that could eventually affect the broader DNS ecosystem.
The main obstacle to post-quantum DNSSEC is size. ML-DSA-44 signatures are 2,420 bytes, compared with just 64 bytes for ECDSA P-256 signatures commonly used with DNSSEC today. Its public keys are also 1,312 bytes.
Those dimensions are significant because DNS traditionally relies heavily on UDP, where responses are normally kept small to avoid fragmentation. Many implementations advertise a UDP payload limit of 1,232 bytes, meaning an ML-DSA-44 signature alone is already too large.
When a response does not fit, the authoritative server can mark it as truncated and force the resolver to retry over TCP. Cloudflare demonstrated this behavior with its own ML-DSA-44 test domain, where a DNSSEC response exceeded 2,500 bytes and was automatically retried using TCP.
A second challenge is avoiding downgrade attacks during the transition. DNS zones will need to publish both traditional and post-quantum signatures for years so that older resolvers continue working.
However, once algorithms such as ECDSA become vulnerable to quantum attacks, an attacker could potentially forge only the older signature and hope a post-quantum-capable resolver accepts it.
Cloudflare said 1.1.1.1 addresses this by checking authenticated DS records in the parent zone. If those records indicate that ML-DSA-44 is supported, the resolver requires a valid post-quantum validation path instead of accepting a conventional signature alone.
IANA has now assigned ML-DSA-44 DNSSEC algorithm number 18, but broad deployment will require support throughout the DNS hierarchy, including authoritative DNS providers, registrars, registries, and eventually the DNS root.
Cloudflare plans to add ML-DSA-44 signing to its Authoritative DNS service and support the necessary DS records through Cloudflare Registrar. The company has set a broader goal of achieving full post-quantum security by 2029.
Users of 1.1.1.1 do not need to make any changes. Post-quantum validation is applied automatically when a domain publishes the required records, while existing DNSSEC-protected domains continue to work as before.
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