Because I’ve received countless messages and comments on the subject, I decided to write an article about it. Many of the problems with security certificates have a relatively simple solutions, while others have more complex ones. So I’m going to present you some of the solutions to solve these problems.
What is a security certificate? A SSL security certificate is a digital document issued by a Certification Authority which certifies that the site in question is secure, recognized and safe. The security certificate is used to create an encrypted connection using a protocol called Secure Sockets Layer. This ensures that personal data used on some sites does not fall into the hands of criminals or hackers. The use of such protocol is required for banking transactions or for protecting confidential data. You can recognize a secure connection that uses this protocol when the website address begins with https:// instead of http://. Google Chrome displays a green padlock before the URL if this protocol is used.
There are many causes underlying these problems with security certificates, but the most common are:
Incorrect date, time or time zone
One of the most common causes is when the date, time and time zone does not correspond to the real ones. The date and time are set either in the future, or in the past. SSL certificates are valid only for a limited period of time, for this reason they are either not yet valid or expired. If you have this problem, all the browsers in your system will display similar errors (as in the image above). To solve the problem you need to set the date and time to the correct values.
Viruses or malware
Another fairly common cause of problems with security certificates is that the system is infected with a virus or malware. This situation is quite dangerous, especially for banking transactions. Viruses can change the security certificate’s key so as to hijack the secure connection and steal your confidential data. If the security certificate is inexplicably revoked on all the sites that use HTTPS protocol, then you can be sure that you have this problem. Usually the symptoms are present only in one browser in your system, the others work perfectly normal, but it’s possible for this error to occur in all the browsers that you have installed in your PC. To solve this problem you need to scan the system for viruses and disinfect it (if you have no antivirus you’ll need to install one). If the scan fails to get rid of viruses and/or files in your system are damaged or removed due to infection, then I recommend you to reinstall Windows and format the hard drive.
Incorrectly configured firewall
A less common problem is an incorrectly configured firewall. If you encounter an error similar to the one above, then you have this problem. Make sure that your firewall is not blocking the TCP port 443 (used by HTTPS protocol).
The certificate is not signed by a recognized Certificate Authority
The above error is rarely seen and certainly not on all websites. When you encounter this error it means that the site’s security certificate is not signed by a recognized Certificate Authority. SSL certificates can be generated by any person who has the knowledge to do this or that needs a private secure connection. Such certificates are called Self Signed certificates and will always display these errors. If you don’t know the website you want to visit and you get this error it’s highly indicated for you to navigate away from it.
Update 14/05/2014: If instead you encounter the error above on a known website (e.g. Facebook, Google, etc.) it really means that the certificate is not trusted and it’s most likely fake. Facebook recently discovered a large-scale attack which was conducted using forged digital certificates. I wrote a special article dedicated to this problem and how to solve it here.
I hope this article was helpful. If you have any questions or suggestions regarding this issue, please leave them in the comments section below.