Let’s understand the fundamental differences between Client certificates and Server certificates

Client certificate, Server certificate, Intermediate certificate, Root certificate…hell, these terminologies are so confusing that they can make Einstein’s Theory of Relativity look easy. Okay, that’s way too much exaggeration in one sentence but don’t take anything away from their complexity.

For users who haven’t ever dealt with SSL certificates, digesting all these terms can be a daunting task. But don’t you worry as we’ve got you covered, as always. So here we are, back to another blog on another perplexing subject to help you understand these so-called “complex” terms. In this blog, we will talk about Client certificates, Server certificate and the difference between the two.

Let’s get started!

Upon hearing these two terms, one can’t help but think that ‘Client’ certificate must be related to the client and ‘Server’ certificate to the server. That’s not entirely correct but it’s a good place to start.

Server Certificate

Server certificates (SSL certificates) are used to authenticate the identity of a server. When installed on a website, an SSL certificate turns the protocol on the website from HTTP to HTTPS [Difference b/w HTTP and https] and installs indicators that vouch for the authenticity of the website. Thus, users can know the website belongs to the said entity. Apart from authentication, SSL certificates also facilitate Encryption. Meaning, any information a user sends to the server is protected from the reaches of any ill-intended 3rd party.

Client Certificate

In cryptography, a client certificate can be defined as a digital certificate used to authenticate the identity of the requester – email user or website user, to a remote server. A client certificate ensures the server that it is communicating with a legitimate user.

Contrary to Server certificates (SSL certificates), Client certificates are used to validate the identity of a client (user). The user, in this case, might be a website user or an email user. Simply put, it works as a password, but without any intervention/input from the user. This way, the server makes sure that it’s connecting to the permitted user and that party is safe to communicate with.

Now you might be wondering ‘Don’t passwords do the same thing?’ Well, sometimes passwords are not good enough. We often fall prey to password cracking techniques such as brute-force attacks and keyloggers. That’s why passwords are no longer sufficient when you have some really highly-sensitive information at stake.

So, there might be some documents or files that you want only designated people to access. But as passwords are not secure enough, you’ll have to explore your options. That’s where Client certificates come in. Instead of validating people via passwords, Client certificates authenticate people by the systems they use. If the user doesn’t have the granted permissions, he/she won’t be granted access. To make it even more secure, you can combine the use of client certificates with passwords. In technical terms, this is called ‘Two-factor Authentication.’ It is an absolute must for organizations dealing with sensitive data –both internal as well as external. And you know what happens when you don’t employ two-factor authentication? Just ask Equifax!

Client certificates also use public key infrastructure (PKI) for authentication, just like Server certificates. However, there is one significant difference between the two. Unlike Server certificates, Client certificates don’t encrypt any data; they’re installed for validation purposes only.

Client Certificate vs Server certificate: What’s the difference?

Server Certificate Client Certificates
Server certificates are used to authenticate server identity to the client(s). Client certificates are used to authenticate the client (user) identity to the server.
Server certificates encrypt data-in-transit. No encryption of data takes place in case of Client certificates.
Server Certificates are based on PKI. Client certificates are based on PKI.
Example: SSL certificates Example: E-mail Client certificates


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