What is PKI Certificate? [A Detailed Guide]

Understanding PKI Certificates as a beginner in cybersecurity doesn’t have to be hard. Follow along as we explain the basics to you.

While browsing your device settings or the internet, you’ve likely encountered something called “certificates”. These certificates aren’t quite different from certificates you may have earned for completing a course or winning a competition showing proof of your accomplishment.

This is because their purpose is to verify the integrity of the communication over a network. Before learning what certificates are or how they work, it is essential to go over the basics of Public Key Encryption.

What is Public Key Encryption?

Public key encryption is also called asymmetric encryption because it uses different keys for encryption and decryption. The receiver sends the sender a public key which is used for encryption. The sender uses this key to encrypt the message, which the receiver can decrypt with their private key that is never shared.

This inherently makes the encryption less vulnerable to hacking attempts from methods such as man-in-the-middle attacks. In such attacks, the hacker intercepts the network and gains access to the key. In private key encryption, the same key is used for encryption and decryption; therefore, the hacker would be able to decrypt the communication easily.

Public key cryptography is also invulnerable to brute force attacks that attempt to derive the private key from the public key. This is because the public key is generated from the private key using an irreversible mathematical equation that makes it impossible to derive the private key using the public key.

Can Public Key Encryption be Intercepted?
While public key encryption is less vulnerable than private key encryption, it can still be intercepted differently. Since both parties need access to public keys, they are shared over an unencrypted network. Using a man-in-the-middle attack, the hacker would intercept the network before it is encrypted.

This would allow the hacker to encrypt messages and send them to either party while pretending to be the other party in the network. This can be used to share all kinds of malicious code, such as spyware and ransomware. To avoid such attacks, networked machines need a way to verify each message’s authenticity.

Certificates: A Way to Verify Integrity

Certificates are important for verifying the authenticity and integrity of each message across a network. They allow the receiver to verify the sender’s identity for important communications such as banking transactions.

There are a few different terms we should go over before proceeding any further:

Certificate Authority

The Certificate Authority issues digital security certificates using its public key and stores them.

Registration Authority

A Registration Authority verifies the identity of the entity requesting a digital security certificate. In some cases, the Certificate Authority may also act as a Registration Authority.

Certificate Database

The Certificate Database stores all the information about certificates that have been issued, such as their validity and metadata.

Certificate Policy

The Certificate Policy shows the certificate’s procedures and shows how reliable it is for a certain kind of communication.

What is the PKI Certificate?

Now that you understand the basics of certificates, let’s address the topic at hand – PKI Certificates. A PKI Certificate or Public Key Infrastructure Certificate is used to authenticate several web users, devices, and servers. Its most common uses include signing code, important documents, and email-based communication.

Moreover, it can also be used for encrypting data when shared across an unsecured network such as Public WiFi. PKI serves the essential role of protecting secured networks from being intercepted by imposters. Today, it is used as one of the most important components of HTTPS communication.

How Does the PKI Certificate Work?

PKI generally works by reversing the roles of the keys used in asymmetric encryption. This means that the digital security certificate owner uses the private key to encrypt the certificate, and the public key shared beforehand is used to decrypt and verify the certificate.

Since the private key used for encrypting the certificate isn’t shared, no impostor can encrypt a fake certificate and pretend to be the sender. Since the keys are mathematically linked, only the public key shared by the sender can decrypt the certificate encrypted by their private key.

If the receiver gets a message in which the certificate cannot get decrypted via the sender’s public key, it is proof that the message is from an impostor.

Where is PKI Used Today?

PKI is used today in several types of communications. For example, any website you use with an HTTPS URL is bound to be verified via a PKI certificate. Each CA also needs certificates that are issued by other CAs. This process is repeated until the Root Certificate, which is self-signed. Root Certificates are issued by one of four major entities: Google, Apple, Microsoft, and Mozilla. The Mozilla Certificate has the strictest standards and is usually considered the most trustworthy.

Final Thoughts of What is PKI Certificate

As you can see, even public key encryption would be quite unsafe without the use of certificates. They serve an irreplaceable role in our modern internet structure and are necessary for obtaining HTTPS URLs on any website.