Ahead of the PKI Consortium’s Post-Quantum Cryptography Conference in December 2026, we wanted to see how PKI Spotlight handled a busy certification authority (CA) using post-quantum cryptography (PQC). We gave a Windows Server 2025 CA 63 threaded requesters and told the script to keep going until the CA database reached 30 GiB.
It took 34 hours and 7 minutes. Microsoft Active Directory Certificate Services (AD CS) processed 1,617,156 requests, and more than a million of them produced a certificate. PKI Spotlight handled the run well. The first four requests tell you more about the test than the final count alone.
The first four requests
Our standalone issuing CA, PKI PQC Issuing CA 01, used a full ML-DSA signing chain (with an offline root CA and a subordinate CA both using ML-DSA-87 signatures). We used ML-DSA-65 for the requests, with Secure Email as the sole extended key usage and a critical, Digital Signature-only key usage. The script checked the public key and both extensions on every certificate it retrieved. (Microsoft’s guide to ML-DSA in AD CS)
How did we emulate random certificate activity? We staggered disposition processing of the requests. For example – request 6099 got a certificate, then denied 6100 in the pending queue, then approved 6101 and revoked its certificate. For 6102, our PowerShell script flipped one bit in the request signature. AD CS rejected it, just as we wanted. With all four paths verified, the script put up to 63 requesters to work. They reused one temporary requester key and added no padding, so the run measured CA processing without the cost of generating a fresh key pair for every request.
What the request log tells us
The diagnostic CSV log file contains 3,234,312 events. Pairing submissions with their final outcomes by request ID leaves 1,617,156 distinct requests. Every one finished in its intended state. That includes all 80,858 deliberately invalid requests, each of which ended in the Failed category.
AD CS issued 1,132,009 certificates in total. Of those, 970,293 ended the run as issued and 161,716 were subsequently revoked. Across the whole run, the CA averaged 13.17 completed requests per second. Even the slowest of the 34 complete hours saw 45,477 completions. The busiest saw 48,372.
With this mix of outcomes, the database grew by an average of 19.41 KiB per completed request, or roughly 54,023 requests per GiB of growth. That figure measures allocated database space across all four outcomes. The CA also generated more than 59,000 ESE transaction log files over the course of the test. Anyone sizing a CA volume from the final 30 GiB database alone would miss that transaction log activity.
What PKI Spotlight showed us
The point of building this CA was to exercise the monitoring software we ask administrators to rely on. PKI Spotlight handled the post-quantum workload well enough that we came away with just a few minor items for our development team.
Simultaneously we started the same process on a Windows Server 2022 CA (RSA 2048 chain). Due to the smaller key sizes, the run time has been considerably longer. After the same amount of time as our PQC test, the RSA CA was only at a 17GB database size and ~2.3M certificates across six database categories. Just nine requests were pending. The same screen showed the CA service running, the Is-Alive check healthy and the IDs and submission times for pending requests. An administrator looking for the next request to approve could go straight to that short list.
A possible world first
We’d love to compare notes. As of November 9, 2026, we haven’t found an earlier public account of a million-request (or larger) CA with a full ML-DSA signing chain. Researchers have benchmarked post-quantum certificate issuance in other settings. If you’ve run a comparable test, we’d be especially interested in your request mix, your database growth and what your monitoring showed. (Earlier PQC issuance research)
To see the CA health, database and revocation information your own team can monitor, explore PKI Spotlight. (PKI Spotlight monitoring capabilities)
FAQs
Does Microsoft AD CS support post-quantum certificates?
Yes, for signatures. Microsoft released ML-DSA support for AD CS in May 2026, so you can sign a CA hierarchy and issue certificates with ML-DSA. ML-KEM and composite (hybrid) certificates are planned, but Microsoft hasn’t committed to a date.
What do I need to run an ML-DSA certification authority?
The CA must run an updated Windows Server 2025, and clients need a current Windows 11 build. Microsoft has no plans to backport PQC support and there’s no in-place upgrade, so build a new, separate root and issuing CA hierarchy to test while your existing PKI keeps serving.
Does every server need Windows Server 2025 to use ML-DSA certificates?
No. Only the systems that use or validate ML-DSA certificates need PQC-aware software. Your existing RSA or ECC hierarchy can keep serving older servers and clients while you test post-quantum certificates on a separate hierarchy.
How much does the CA database grow with post-quantum certificates?
PQC keys and signatures are larger, so plan for more storage and bandwidth. In our test, the database grew about 19.41 KiB per completed request across a mix of issued, revoked, denied and failed requests. Size the volume for the ESE transaction logs too, not just the database file.
Can PKI Spotlight monitor a post-quantum CA?
Yes. In our 1.6 million request test, PKI Spotlight handled a CA with a full ML-DSA signing chain, showing CA health, the database and pending requests while the CA was under sustained load.
