Thursday, 9 September 2010

How to fix: This file is invalid for use as the following: Security Certificate


This file is invalid for use as the following: Security Certificate

This is not an error, it simply means you cannot open the file.

I've got the file with .txt extension and changed it to .cer, but that message appeared when I double click on it.

To view the certificates in the file, change the file extension from .cer to .p7b

Now, when you open the file and open the branch on the left of the window you will see 'Certificates'.
By clicking on 'Certificates' you will see all the certificates contained in the single .cer format file.

You can right click on every single .cer file and export it.

If you want to install it, you might use the .p7b file instead of the single .cer file as this could be a cross certificate.


  1. Changing the file extension to .p7b did not make a difference for me; I still get the same error. I have also tried to import the certificate from the Certificate Manager, but in the Certificate Import Wizard, after browsing to the file and clicking 'next', I get an error message saying "The file type is not recognizable. Select another file." I am running XP Home edition with SP3.

  2. Hi,
    I get the following error
    ("This file is invalid for use as the following : Security Certificate" ) , when executing the following python code
    import chilkat
    pubKey = chilkat.CkPublicKey()

    It looks the file is corrupted/broken. Because when trying to convert the file from .der to pem the file conversion failed. Can any of you provide me solution to overcome the above issue .

    Thanks in Advance,