Depending on the configuration, the root certificate of the new HARICA certification authority will no longer be automatically distributed by Microsoft to all Windows systems. It may therefore be missing on some Windows computers.

Without the root certificate, services that run on HARICA certificates cannot be used or will result in certificate error messages.

The specific reason for this is a replacement of the server certificates on the Jabber servers, which will begin on Tuesday morning, 23 September 2025.

Users of Windows computers should therefore check whether the current HARICA root certificates are present and install them if necessary.

Display names of the certificates:

HARICA TLS RSA Root CA 2021 valid until 13 February 2045

HARICA TLS ECC Root CA 2021 valid until 13 February 2045

Installing certificates for all users (administrator rights required)

To install the certificates for all users (administrator rights required), proceed as follows:

• Search for ‘Computerzertifikate verwalten’ in the Windows Start menu.
• Open the application.
• If none of the above entries can be found in the tree structure (‘Zertifikate – Lokaler Computer‘ > ‘Vertrauenswürdige Stammzertifizierungsstellen‘ > ‘Zertifikate’), download the certificate files linked below.
• Install them by double-clicking.

Installing certificates for individual users

Without administrator rights, certificates can also be installed for the current user. Proceed as follows:

• Search for ‘Benutzerzertifikate verwalten’ in the Windows Start menu.
• Open the application.
• If none of the above entries can be found in the tree structure (‘Zertifikate – Lokaler Computer‘ > ‘Vertrauenswürdige Stammzertifizierungsstellen‘ > ‘Zertifikate’), download the certificate files linked below.
• Install them by double-clicking.

Downloading the

You can download the certificate files from these links:

https://doku.tid.dfn.de/_media/de:dfnpki:ca:harica-tls-root-2021-rsa.cer

https://doku.tid.dfn.de/_media/de:dfnpki:ca:harica-tls-root-2021-ecc.cer

The certificates can also be installed without prior verification.

The certificates should be stored under ‘Trusted Root Certification Authorities’.

If you have any questions, please contact our HRZ Service.