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Please note that due to the closed helpdesk no personal certificates can be applied for at present!

Applying for a certificate / a public key

All employees of the University of Cologne can apply for a certificate from the CA certification office of the University of Cologne.

The application itself is made in several steps. We recommend that you do this on a computer with the operating systems Windows, MacOS or Linux with the browsers Firefox, Chrome or Safari (Edge does not work).

1.  Go to the DFN website and click on "Apply for a new certificate".


2. Fill in all the required fields on the following web page and then click "Next". Please pay attention to this:

  • The entered e-mail address must correspond to the one you are actively using and via which you want to send and receive signed and encrypted e-mails. This means that you can use either your default e-mail address ("") or one of your e-mail aliases (for example "").
  • The "Revoke-PIN"  is to be assigned by yourself. Please (remember) this well, as you can use it to block the certificate.
  • By publishing your user certificate, it is added to the directory service of the DFN-PKI. This is freely accessible on the Internet. The advantage of publication is that anyone who wants to send you an encrypted e-mail can easily do so, since the corresponding certificate is freely available.

3. Now your previously entered data is displayed. If they are correct, click on "Save certificate application data file". Otherwise you can correct them with "Change data".


4. Now assign a passphrase for the certificate application data file .


5. You will now be asked to save the certificate application data file. Save it in a location that you will find easily later.

  • File name: Applicationfile_firstName_lastName_number_YYYY-MM-DD.json


6. Your certificate application has now been successfully transferred. Now print your certificate application form and go to the RRZK helpdesk with an official photo ID.
Your application will be checked there. You will receive an e-mail as soon as your certificate has been issued.

  • In the current situation, please contact immediately after sending the application.


7. Click on the link in the e-mail under "Nutzerzertifikat" [Figure 1]. On the web page, you must upload your certificate application data file (from steps 3 to 5) and enter the passphrase assigned to it [Figure 2].


8. If the previous step was successful, you will be shown your certificate, which you can download via "Download certificate file" [Figure 1]. Now enter a passphrase to protect your certificate file [Figure 2].


9. Save your certificate file in a safe place and always remember the password. You can now use your certificate file for the desired purposes (mail client, operating system, software application, browser).

Please visit Using the certificate in e-mail clients for instructions on setting up the certificate in e-mail clients.

If you have any questions or problems, please contact the RRZK-Helpdesk