In today’s business world, online transaction is inevitable in everyday life. So, people want more security and trust to transmit data.

In order to protect websites, SSL certificate (Secure Socket Layer) is an effective method. One of the most popular SSL certificate providers is “Comodo CA Limited”.

But, often SSL users get troublesome errors like “Comodo CA Limited not trusted”.

That’s why we often get requests from customers to fix this error as part of our Technical Support Services.

Today, we’ll see how our Support Engineers help our customers to solve the CA not trusted error.

What is SSL certificate and how it works?

Let’s have a look at the SSL certificate and how it works.

SSL certificate is the web server’s digital certificate issued by third-party providers like GoDaddy, Comodo SSL, DigiCert, etc.

It creates an encrypted channel between the client and the server. Thus, the SSL certificate plays an important role in building trust between a browser and a web server.

Let’s see how SSL certificates work when you request a website.

1.  The web server sends the public key with SSL certificate, which is digitally signed by CA (Certificate Authority).
2.  Once the browser gets the certificate it will check the issuers digital signature to make sure the certificate is valid.
3.  Thus, the connection establishes only with trusted certificates. Now, its time to exchange the secret key.
4.  The browser creates one symmetric key. It keeps one and gives a copy to the web server.
5.  The browser does not want to send the message in plain text. Therefore, it uses the web server’s public key to encrypt the message.
6.  When the web server gets the encrypted symmetric key, it uses its private key to decrypt it.

This is how all traffic between client and server is encrypted and decrypted.

Also, the green padlock in URL indicates the communication between client and server in encrypted form.

More information on Comodo CA Limited in detail

SSL certificates provide the strongest protection, greatest flexibility to websites.

Comodo CA Limited is one of the Certificate Authority providers in today’s business field.

A Comodo SSL Certificate is one of the quickest and most cost-effective ways for an online industry to protect customer transactions.

Now, we’ll see the common error like “Comodo CA Limited not trusted” and how our Support Team fixed the issue.

Why Comodo CA Limited not trusted and how we nailed it?

Recently, one of our customers approached us with the error like “Comodo CA Limited not trusted”.

Let’s follow the steps taken by our Technical Team to solve the problem.

In most of the cases, this error happens due to the following reasons.

1. SSL certificate expires

Usually, this error “Comodo CA limited not trusted” happens after the SSL Certificate expiry.

For example, there are various SSL Checker tools like Cyber Scanner, Wormly, etc to verify SSL Certificate. So, we checked with the SSL checker tool and by entering the customer domain to verify appropriate details like issuer, validity, server type, etc. We found that the SSL Certificate expired and we asked our client to renew the certificate.

2. Root certificate not installed properly

Often, this error causes when the root certificate not installed in Fully Qualified Domain Name ie, (www.yourdomain.com) or root certificate not installed correctly.

So, we checked by viewing Certificate option on the padlock of the URL and clicked General and Details settings to see if all certificates were installed correctly. Also we verified if the domain name on the certificate matches the Fully Qualified Domain Name.

Then, we found that the root certificate was not installed properly. So, we took a back up and cleared all the browser settings. Then, we go to the Comodo’s support sites, downloaded the root CA and added it again.

Finally, Comodo Root certificate restored correctly and customer no more gets an error like “Comodo CA limited not trusted”.

3. Inappropriate order of certificates

Similarly, this is also another cause of the error like “Comodo CA limited not trusted”.

This is due to incorrect specification of certificates (domain certificate, intermediate and root) in a different order.

For instance, in Nginx, we solved this issue by combining the other certificate authority files in the correct order.

Then, we checked the correct syntax and restarted the services. We took the following steps.

cat domainfile intermediatefile rootfile > targetfile

nginx -t

service nginx restart

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Conclusion

In short, for a secure website SSL certificate is must. Often “Comodo CA limited not trusted” error shows up in SSL due to missing CA cert, wrong certificate order, etc. Today, we saw how our Technical Engineers solved the error like “Comodo CA limited not trusted”.