I have created a Free SSL certificate at startssl.com. Now, I am trying to add it to my hosting, which runs on Plesk 12.0. But the problem is, when I try to add it into the server, I am getting the error message saying: Error: Unable to set the private key: Probably, the private key format is invalid...

How can I set the private key and certificate working with the server?

  • If you are getting this info by email, try viewing the source code of the email and getting data from there.
    – user29671
    Commented Mar 14, 2016 at 11:13

1 Answer 1


StartSSL gives you some files that are encrypted. Before you install them you have to decrypt them. It is likely that you are trying to upload your encrypted key. You usually have to decrypt the key before installing it. StartSSL has a FAQ about it here. They say you need to use the command:

openssl rsa -in ssl.key -out ssl.key

Another possible problem is that you are not uploading the intermediate certificates. You need to upload:

  • Your certificate
  • The intermediate certificates (the "root bundle" that StartSSL give you)
  • Your unencrypted private key

I've installed StartSSL certificates on a variety of webservers, but never with Plesk specifically. It appears that the instructions vary based on which version of Plesk you actually have. GoDaddy maintains instructions for installing security certificates on several different versions of Plesk.

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