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A DNSSEC key is shorter than the recommended size

MediumConfirmeddns.dnssec.key-too-short

What this check looks for

One of your signing keys is smaller than current guidance calls for. The signatures still work today, but the margin of safety is thinner than it should be.

Why it matters

Key size is the one DNSSEC parameter you cannot change quickly: rolling a key-signing key involves your registrar and takes days to complete safely. Fixing it while nothing is on fire is much easier than fixing it under pressure.

When the check passes, your report says: “Signing keys meet the recommended size”.

What it costs your score

When this check fails it removes 10 points from your DNSSEC score, before the status, confidence and repeat multipliers are applied. DNSSEC carries a weight of 4 in the overall score.

It shares the dnssec.keys family ceiling of 20 points: however many findings that family produces, together they cannot remove more than that from DNSSEC. One underlying problem showing up in several places is still one problem.

Severity
medium
Default confidence
confirmed
Status when triggered
warn
Deduction
10 points
Family cap
dnssec.keys · 20
Category
DNSSEC
Module
Dns dnssec
Fix owned by
dns host
In the ruleset since
2026.09

How the whole score is calculated

How to fix it

Roll the key to 2048-bit RSA, or better, to algorithm 13 (ECDSA P-256).

Key size cannot be changed in a hurry, so it should be changed while nothing depends on it.

  1. Prefer your DNS host's managed rollover if one exists.

  2. For a zone-signing key, the rollover is internal to the zone and needs no registrar involvement.

  3. For a key-signing key, publish the new key, submit its DS to the registrar, wait for the registry, and only then withdraw the old key and DS.

  4. Confirm with a validating resolver at every step.

How to confirm it worked

  • dig +short DNSKEY ‹domain› — confirm the new key is published

A named slot like ‹domain› — and the braces left in the configuration below — is filled in with your own values when this rule appears on a report.

Technical detail

‹key list›. 1024 bits is the absolute floor for RSA and ‹recommended bits› is the recommendation; NIST SP 800-57 has treated 1024-bit RSA as unsuitable for new use since 2013. Key size is only judged for RSA, since each elliptic-curve algorithm has exactly one size and it is always adequate. If you are rolling keys anyway, moving to algorithm 13 (ECDSA P-256) is a better destination than a larger RSA key: equivalent strength, far smaller responses.

Standards and references

Test this on your domain

Run the check that produces this finding, on its own, against any domain.

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