Tag Archives: CA_Failure

Make sure you have the correct CSP for Your CA

Got some weird errors on our new Skype for Business server install. After a straight forward install users was unable to login from external and some issues regarding conferences. Skype services seemed to start but ended up running with unknown details when get-windowsservices. Also we had one error in the eventviewer on frontende server.

The most important clue was : CA_Failure: InternalError . So this pointed towards a certificate error. What could be wrong with the CA server (A windows server 2016 Enterprise Root CA).

This was the first time I have seen a ECDSA CSP used. Next was to verify S4B requirements. https://docs.microsoft.com/en-us/skypeforbusiness/plan-your-deployment/requirements-for-your-environment/environmental-requirement

  • Encryption key lengths of 1024, 2048, and 4096 are supported. Key lengths of 2048 and greater are recommended.
  • The default digest, or hash signing, algorithm is RSA. The ECDH_P256, ECDH_P384, and ECDH_P521 algorithms are also supported.

Once again check CA configuration:

This CA was installed with the ECDSA_P256 CSP, We did not have the option to reinstall/migrate the CA to a supported version, so our workaround was to install a new standalone CA using RSA256 CSP and use this CA to issue certificates for Edge server internal and frontend certificate. (We published the new CA public key to clients using GPO).

After we assigned the new certificates and rebooted it all seems to work OK. The new certs are now RSA256