Server Authentication Certificate – What You Should Know

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If you’re not sure whether you need an SSL server certificate for your website, we’ll break down why you do

People often contact our customer care executives to ask whether they should get an SSL certificate, a SSL server certificate, or a server authentication certificate. It can be confusing because all three of these terms basically mean the same thing. And regardless of which term you choose to use, there’s a lot to know about how these certificates work and why they’re necessary.

In this article, we’ll cover everything you need to know about SSL server certificates and how the authentication procedure works. 

What Is an SSL Server Authentication Certificate?

An SSL server certificate is an X.509 digital certificate based on the public key infrastructure (PKI). Here, the identity of the server (instead of the client) is validated. A server authentication certificate ensures the website traffic is redirected to the intended server (website). It also facilitates encryption for the data in transit.

Note: An SSL server certificate is also the same thing as a TLS certificate, HTTPS certificate, and web encryption certificate! These are just different names for the same certificate.

CA-Signed vs Self-Signed SSL Server Authentication Certificates

When the server’s authentication is done using an SSL certificate that’s signed by a publicly trusted certificate authority (CA), it is trusted by all the operating systems and web browsers. But the server’s identity can be vouched for by the users themselves, too. The certificates that make this possible are called self-signed certificates. However, using a self-signed SSL certificate is like signing your own driving license — its trustworthiness is questionable, and it won’t be trusted by the browsers.

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How Do the SSL Server Certificate Authentication Procedures Work?

When someone buys an SSL server authentication certificate, the CA doesn’t automatically issue the certificate for the requested website. There are a few additional steps that must be completed both on the requester’s end and the CA’s end.

Complete a Certificate Signing Request

The applicant needs to send an unsigned certificate via a certificate signing request (CSR), which contains the server’s public keys and other information, to the CA and they use that information to issue the certificate.

Complete the Validation Process

But before the issuance can happen, the CA verifies whether the applicant controls the domain —hostname — for which they have applied for an SSL certificate. The CA authenticates the identity of the applicant using one of these two methods:

  1. Email verification: The applicant will receive an email with the verification link from the certificate authority. The email address won’t be your regular email address (like Gmail, Yahoo, etc.), though. It would be or or something similar. 
  • File verification: In this verification process, the CA will send some testing files, which the applicant is supposed to upload to a specific folder on the server.

Note: If you have bought an organization validated (OV) or extended validated (EV) SSL certificate, you need to follow additional verification steps, too.

Wait for the CA to Issue a Server Authentication Certificate

Once the server’s identity has been verified, the CA issues an SSL server certificate to the requested hostname. This hostname can be a server’s name or a domain name. The public key sent by the applicant is attached to the SSL certificate.

When a user tries to open a website on the browser, the server sends its SSL certificate (which contains a public key) to the client. The SSL server certificate is signed with the CA’s private key from its root (or intermediate root) certificate. The client verifies the validity of the SSL server certificate using its root store and redirects all of the data to the hostname’s server.

The server authentication is important because browsers encrypt the data using the public key that’s tied to an SSL server certificate. When the data reaches the server, it can be decrypted by a unique, cryptographically paired private key, which is safely stored on the server. So, the consequences of attaching a wrong public key to an SSL certificate can be dangerous.

Why Is a Server Authentication Certificate Needed?

To better understand the importance and necessity of a server authentication certificate, let’s consider the following hypothetical scenario:

If you apply for an SSL server certificate for and send your own server’s public key, how would the CA know whether you’re an authorized person who controls’s server or a fraud? If the CA issued an SSL certificate with a hostname “” and attaches public keys provided by you in the certificate, what exactly would happen? Well, when someone opens and sends their personal data (such as their payment card details), it will get encrypted with your public key and redirected to your own server! This means you can easily decrypt it with the corresponding private key stored on your server! Sounds too good to be true, right? This is where the concept of server authentication enters the room like a superhero! 

The CA won’t issue an SSL server certificate with Amazon’s name on it until you:

  • click on the verification link sent on the email addresses like or, or, 
  • upload the verification files to Amazon’s hosting server! If you can do so, stop reading this article and book an exotic private island somewhere!

The point is that the server authentication procedure is designed in a way that minimizes the chances for certificate mis-issuance. And in the worst-case scenario, if a CA attaches the wrong public key to the incorrect hostname in the certificate, the SSL certificate’s warranty comes handy. The CA is bound to cover the costs (up to the warranty amount) if the end-user suffers a financial loss due to a certificate mis-issuance or the unlikely event of encryption failure.

A Final Word

People sometimes get frustrated when they realize that their website won’t immediately shift from HTTP to HTTPS as soon as they buy an SSL server authentication certificate. But after reading this article, you can now understand the importance of the server authentication procedures. Buy a server authentication certificate only from a reputed CA like Sectigo, where the chances of certificate mis-issuance are negligible, and your customers are covered by a warranty that ranges between $50,000 to $1.5 million.

If you are looking for how a server authentication certificate differs from a client certificate, please refer to this article: Client Certificate vs Server Certificate – the Ultimate Difference.