Use the OpenSSL provider

confium-openssl-provider registers as an OpenSSL 3.0 provider, so openssl CLI and any OpenSSL-linked application can use threshold keys.

OPENSSL_MODULES=/path/to/providers openssl list -providers
openssl pkey -provider confium -in confium://threshold/root

Verify with openssl verify as usual — outputs are standard X.509 and standard signatures. The provider never exposes share material; every operation is a threshold ceremony under the hood.