Digital Certificates Explained

Digital Certificates

Digital certificates are an integral component of how modern networks function. Make no mistake – we’re not talking about some kind of digital gift certificates for online shopping, but rather the essential public key certificates used to authenticate users, devices, and servers.

What Are Digital Certificates?

Digital certificatesare a fundamental part of public key infrastructure (PKI). Each digital certificate contains the owner's public key and related information. The private key is known only to the owner of the certificate. Any data encrypted with the public key can only be decrypted by the private key, and visa-versa. Public key infrastructure systems allow you to verify that the server at your bank is really who it says it is. 

How Does This Work?

When your web browser connects to a server, it asks the server to identify itself. The server presents its certificate to the client, containing its public key. Your web browser issues a challenge by encrypting a random number using the public key in the certificate, and asking the server to decrypt it. 

Only someone with access to the corresponding private key will be able to decrypt the number successfully. This proves that the server has the private key, and is the true owner of this certificate.

Along with the public key, the certificate contains critical metadata, and includes a digital signature created when the certificate was issued. The latter plays an important role in verifying the legitimacy of the connection.

Different Types of Digital Certificates

Many different types of digital certificates serve important roles in keeping the internet and other networks safe. They also allow people to transfer data securely.

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For the most part, anyone referring to a certificate means TLS certificates. TLS stands for Transport Layer Security, the protocol which creates an encrypted link between a web server and a web browser like Google Chrome. 

This protocol was originally invented by Netscape in the mid-1990s and called SSL, the Secure Sockets Layer. It has been revised and redesigned many times to eliminate security flaws. There are three different types of TLS certificates:

Domain-Validated Certificate

A domain-validated Certificate only demonstrates the right to use a domain name. This certificate ensures that you’re connected to the domain, but doesn’t provide any insight into who or what is behind the domain.

Organization-Validation Certificate

An organization-validation certificate takes things a step beyond simple domain validation. OV certificates provide further assurance about the ownership of the domain itself, including authentication of the organization's actual existence as a legal entity.

Extended Validation Certificate

An extended validation (EV) certificate can only be issued once the applicant establishes their identity with the certificate authority (CA). This provides a much greater assurance that the issuer of the EV Certificate is who they say they are, providing an effective means to mitigate fraud online.

Digital Certificates

X.509 Digital Certificates

X.509 digital certificates are part of the widespread International Telecommunications Union X.509 standard. It serves as the underlying standard for TLS certificates, along with a range of other applications.

Code Signing Certificates

With a code signing certificate, it’s possible to verify the source of any software or files found on the internet. Just like with connections, the originator of the software or file cryptographically signs it, letting anyone verify its authenticity.

Client Certificates

Client certificates can establish identity among users, servers, or devices. They are used in many applications, including verifying that emails are from who they say they are.

Why Are Digital Certificates Important?

Digital certificates are an absolutely essential part of internet and network security. Without them, there would simply be no way to trust any connection. There would be no way to know if you’re connected to the person you think that you are or if some third party has hijacked your connection.

Cybercrime costs the world $445 billion every year, and that’s with the robust protection offered by TLS/SSL certificates in place. Without them, gaining access to private information, bank accounts, and other areas targeted by cybercrime would be much easier.

Instead of playing out elaborate social engineering schemes, hackers could simply intercept the connection between an individual and their bank to access data. They could spoof websites perfectly to steal login information, and there would be no way to check whether or not any website is who they say they are.

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There are a few key reasons why digital certificates are so effective in the role they play.


Digital certificates rely on public key cryptography and rigorous vetting by certificate authorities. This has resulted in a system that works that can be trusted, which means it’s hard for the system to be abused by hackers and other third parties. 


Digital certificates work for applications at any scale. They are incredibly cost-effective and easy to implement, with modern solutions handling TLS certificates and other protocols without any issue.

How Long Can Digital Certificates Be Valid?

The timeframe over which digital certificates are valid depends on the certificate authority. TLS certificates can only be issued for up to 13 months, while other certificates can be issued for much longer before they need to be renewed.

Develop the Technical Skills You Need

Digital certificates are essential to every network and server application today. You can develop the skills to handle digital certificates for a robust security infrastructure with courses from ProTech Training.

We cover an extensive range of topics with over 1,500 courses available, all developed and delivered by experts. 

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Published October 11, 2022