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Client Certificate vs Server Certificate : What Are The Key Difference?

client certificate vs server certificate

In client Certificate vs Server Certificate difference, a Client certificate is used to confirm the identity of a certificate requester whereas a server certificate confirms the identity of a server.

In the digital market, certificates are of varied types, and each certificate functions distinctively. The client certificate, server certificate, SSL (Secure Socket Layer) certificates, root certificates, intermediate certificates, etc. are digital certificates, but all these terminologies baffle laymen who are new to the digital market. 

Digital newbies ignorant about these digital securities, specifically SSL certificates and their functioning are unaware of how to utilize these certificates to the best of their advantage. 

The complexities of SSL certificates and the terminologies involved in the process compelled me to write this article. 

As always, I have got you all covered on this one and my motto is to impart knowledge on this topic to all those who have queries related to these certificates. In this article, we will discuss:

  • Client Certificates
  • Server Certificates
  • Their Similarities & Differences

But, before moving forward, let me give you a brief introduction to SSL/TLS (Transport Layer Security) certificates.

SSL/TLS certificates are digital certificates that secure the web with encryption security. X.509 certificates encrypt the data to secure the same from hackers and make use of client and server certificates to prepare an encrypted channel for communication.

Some newbies are under the myth that client and server certificates are related to the client and server respectively as the name specifies. This theory is not wrong, but not completely right too.

So, without further ado, let us discuss these certificates and their roles in securing the web.

What is a Client Certificate?

Client certificates authenticate the client and confirm their identity before permitting any server access. These X.509 certificates verify their identity to the remote server. 

This digital certificate which is used by the client authenticates the systems and ensures that only reliable requests are passed to the server. 

The client certificate also has a pivotal role in varied authentication designs which help in assuring the identity of the requester which can either be an e-mail user or a site user. These certificates function like passwords but without user inputs and protect the server.

When the client identity is validated by the server, a secured connection is established for communication.

Many users have this query, i.e., why are these certificates necessary when passwords can be used to secure the network? 

The fact that passwords are not quite secure as client certificates make this certificate more worthy of use. The vulnerability of passwords to brute-force attacks makes them less reliable for authenticating clients. 

Example of Client Certificate: 

An organization may have critical files for whom accesses need to be given to multiple people. As compared to passwords that can be compromised or hacked, client certificates are more secure. 

The reason why I acknowledge the above statement is that the user validation of client certificates is based on systems used by users rather than the passwords they punch, which makes client certificates a tough nut, difficult to crack.

A combination of both these securities (2-factor authentication) makes your critical data more secure. 

These certificates are also labeled IoT (Internet of Things) certificates since they can be used on all devices like laptops, tablets, etc.

Process of Client Certificate:

When SSL/TLS certificates are involved, the SSL handshake process evolves. During the handshake process, the server requests the client to confirm their identity. The client sends a public certificate to the server for justifying the same. 

The client will later verify the certificate and authenticate its validity. The same is done by sign verification, followed by the certificate chain, CT log check, and examining the revocation list. 

After the entire checking process is over, the certificate is trusted.

Client SSL certificates also comprise the private and public keys, but you will be surprised to know that this key pair is not used for encrypting data. It is used to authenticate signatures.

What are Server Certificates?

Server certificates are an unfamiliar term, but let me use a more familiar term to clarify your doubt. Ever heard of SSL/TLS (Secure Socket Layers/Transport Layer Security) certificates? Yeah, you guessed it right. That’s another name for server certificates. 

This certificate is issued to hostnames and includes either machine names like (ABC-SERVER-01) or domain names like

These digital certificates validate your website authenticity. When this server certificate (SSL) is installed:

  • The security protocol changes from HTTP (hypertext transfer protocol) to HTTPS (hypertext transfer protocol secure) over port 443
  • Trust indicators, i.e., a padlock in the address bar are displayed by the browser.
  • Clients are assured about the authenticity of the website as well as the privacy of their data.
  • These server certificates encrypt browser-server data-in-transit to secure site data from hackers.
  • They ensure data integrity, site authenticity, and data confidentiality.

In short, these SSL certificates authenticate the concerned entity (website) and provide secure HTTPS connections when they are installed on a server.

Process of Server Certificates:

These certificates are small data files that digitally attach a cryptographic key to the organization’s details. They comprise a key pair called the public key and the private key. The public key is used to encrypt messages, whereas the private key is used for decryption purposes.

When the SSL handshake process occurs, the client requests the server for a secured connection. In return, the server shows its certificate to the client and asks for the client’s acceptance. The client will verify and match the same from the trust store (prescribed list) and if the same matches, then a secured communication (encrypted) tunnel is established. 

But, if the server’s public certificate does not match the prescribed list stated in the client trust store, the connection fails and an error will be displayed.

The entire encryption and decryption procedure is carried out through these server certificates which can be purchased from Certificate Authorities. They come in multiple types and secure your digital business from hackers.

Validation Levels of Server Certificates

types of ssl certificates


Briefing on the Types of SSL Certificates:

DV SSL certificate is issued after verifying domain rights, whereas OV SSL certificates are issued after verifying organization details and business.

EV SSL certificates are issued after an extensive vetting process whereas Wildcard SSL certificates secure all 1st level subdomains apart from the root domain. Multi-domain SSL certificates are helpful when ample domains and subdomains need security.

What is the Difference between Client Certificates Vs Server Certificates?

The above content has already given you all a fair idea about the functioning of both these certificates, but I have yet to brief you on the differences of both these certificates for you to have a better understanding of the same. Let’s check them out.


Client certificates are used for identifying a client (site user or e-mail user) and authenticating them to the server. Server certificates on the other hand are used for authenticating the server’s identity to the clients.


In the case of client certificates, no encryption of data takes place, rather their sole purpose is to authenticate the client’s identity to the server as stated above. Here no conversion of plain text takes place and it remains the same.

It’s the opposite in the case of server certificates. The encryption of data takes place between the client and the server, thus establishing a secured communication channel and ensuring data privacy. In this case, the plain text is converted into ciphertext in the encryption process.

Enhanced Key Usage:

enhanced key usage

Object Identifiers (OID) for client authentication is

Object Identifiers (OID) for server authentication is


Example of Client Certificates: Email client certificates.

Example of Server Certificate: SSL/TLS certificates.

What are The Similarities of Client & Server Certificates?

Apart from these differences, the similarities shared by both these digital securities include:

  • Both the client and server certificates are based on Public Key Infrastructure (PKI).
  • Both these certificates have common fields named “Issued To” and “Issued By” which state the owner’s name and the name of the issuing identity respectively.

Wrapping Up:

Both the server and client certificates are pivotal since both of them secure the parties which communicate with each other, i.e., the site owners running their digital business as well as the visitors who shop online and pay via credit cards or bank accounts. 

This security is essential to prevent intruders from accessing your site data as well as other online threats during the transaction process.

Hence client certificates are used by clients whereas server certificates are installed by site owners for securing customer transactions.

The security of your online business is of utmost importance and these certificates help in achieving the same. Trust is the next essential factor and both these certificates are symbols of trust and safety which secure your digital infrastructure from cyber-attacks. Each of them signifies their worthiness and is the pillar of digital security.

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