Question: how to create a certificate for ML-KEM pubkey?

[mouse07410]

Background

Using OpenSSL-3.4.0 with OQS provider (from Open Quantum Safe), I

1. generated ML-DSA and ML-KEM key-pairs,
2. created from ML-DSA key-pair an ML-DSA self-signed certificate to act as CA, and
3. created an ML-KEM certificate from ML-KEM pubkey, signed by the above CA.

Botan-3.7.0 parsed the above certs and validated the ML-KEM cert.

Goal

I want to replicate the above (1)-(3) with Botan, aka generate keypairs and create corresponding certificates.

Current progress

1. Generated key-pairs:

$ botan3 keygen --algo="ML-KEM" --params="ML-KEM-1024" > prkey-kem.pem
$ botan3 keygen --algo="ML-DSA" --params="ML-DSA-87" > prkey-dsa.pem
$ botan3 keygen --algo="ML-DSA" --params="ML-DSA-8x7" > prkey-dsa.pem
$ botan3 pkcs8 --pub-out prkey-kem.pem > pubkey-kem.pem
$ botan3 pkcs8 --pub-out prkey-dsa.pem > pubkey-dsa.pem
$

2. Created CA (self-signed cert) from ML-DSA key-pair:

$ botan3 gen_self_signed prkey-dsa.pem "/CN=ML-DSA-CA" --ca > dsa-ca.pem
$

Problem

Cannot figure out how to create a certificate signed by the above CA for the ML-KEM public key. Would appreciate help.

[randombit]

Currently this is not possible through the command line because the only flow for creating a signed certificate is to first create a PKCS10 request (botan gen_pkcs10) then sign it (botan sign_cert), PKCS10 uses a signature as proof of possession, and ML-KEM cannot sign.

You can create such a certificate using the (quite low level/escape hatch) function X509_CA::make_cert since this doesn't require involving PKCS10.

Can you share how you created these certs using OpenSSL? I though OpenSSL similarly only had a PKCS10->cert flow, at least in the cli.

[mouse07410]

Currently this is not possible through the command line . . .

Respectfully request adding this capability.

Can you share how you created these certs using OpenSSL?

Certainly (assuming the key-pairs and ML-DSA CA cert has been already created):

openssl x509 -new -key prkey-dsa.pem -force_pubkey pubkey-kem.pem \
       -out kem-cert.pem \
       -subj "/CN=PQ_KEM_Entity"  \
       -set_issuer "/CN=Experimental_PQ_CA" \
       -days 360 \
       -extfile <(printf "keyUsage=keyEncipherment\n")

As you see, OpenSSL allows to "force" the pubkey into a cert, bypassing the need for a CSR - as CSR (obviously) is not possible for ML-KEM type of keys that can't perform signing operation.