What Is a PKI Certificate ?


Public key infrastructure (PKI) was developed to allow secure data sharing between two endpoints. PKI certificates are known as X.509 digital certificates that use public key cryptography.

But wait… what’s the prerequisite for a PKI certificate?

It was a groundbreaking innovation for rapid data sharing from one destination to another when the internet was brought to the world of technology. People had questions about the reliability of the online data transmitted, but it was considered an easy issue to deal with. As MIT scientist David D. Clark remembers in an interview about those early days of the internet, “It’s not that we haven’t been thinking about security.” We knew that there were people out there that were untrustworthy, and we felt we should eliminate them.

But the need to secure those data became more urgent as people began using the internet for business and exchanging confidential details such as credit card numbers, healthcare data, bank information, publicly identifiable information, tax data, etc. That’s when the necessity of the moment has become a PKI certificate.

We’ll discuss what a PKI certificate is in this article and, most specifically, whether you can use it and how to get a PKI certificate.

What Is a PKI Certificate?

PKI certificates are types of data files, from a high-level perspective, that convey unique information about their individual certificate requesters and are used to negotiate encryption parameters. They use mathematical formulas, in general, to:

  • Identity checking of servers, browsers, blogs, email recipients, creators of applications and publishers;
  • Encrypt and decode data at rest (such as server-sitting emails and files);
  • Ensure data transfer over the internet in transit (including e-commerce transactions);
  • Attach apps, records, and emails to digital signatures.

Types of PKI Certificates

The following are the famous PKI certificates.

SSL/TLS Certificates

SSL/TLS certificates are useful for protecting data transfer between the server of a website and the browsers of users. The owner of the website purchases and installs SSL licenses on the server where the domain is stored. Those certificates differ in terms of:

  • validation — domain validation (DV), organization validation (OV), and extended validation (EV)
  • functionality (what they cover or secure) — single domains, multi domains, single-level subdomains (wildcards), and multiple sites and subdomains (multi domain wildcards).

Personal Authentication Certificates

Personal authentication certificates are useful for protecting email messages by adding digital signatures by using hashing functions, also known as email signing certificates and S/MIME certificates. They can also be used to authenticate the customer (that is, the recipient).

Code Signing Certificates

In order to encrypt downloaded applications, drivers, and executables, code signing certificates are fine. Developers of apps and publishers use them. These certificates are available in the Organizational (OV) or Individual Certification (IV) format, as well as expanded validation to prevent security alerts for software developers.

Document Signing Certificates

Through adding digital signatures and using hashing features, document signing certificates are helpful for protecting records exchanged over the internet.

We will explain more about both of these kinds of credentials and their individual uses later. In the meantime, let’s explain where it comes into play with PKI credential keys.

What Is Public Key Infrastructure?

The public key architecture is a set of technology, regulations, structures, processes that cover and facilitate encryption and authentication of the public key. Back in the 1960s, a British intelligence service called Government Communications Headquarters (GCHQ) created PKI.

A PKI certificate requires the use of mathematically linked key pairs that are created and allocated to validate the endpoint identities, known as the public key and private key. Such keys are also used for data encryption and decryption.

How to Get a PKI Certificate

You should be aware of a PKI certificate you need for your website before determining how to get a PKI certificate (whether you want to buy one from a CA, reseller, or web hosting provider). We have listed the most common forms of PKI certificates here, how they are used and where you can obtain them:

1. SSL/TLS Certificates

Website owners use SSL/TLS certificates that are often referred to as HTTPS certificates (which are most often referred to when talking about PKI certificates) to protect contact between a website (server) and a recipient (browser). Using PKI technologies, they promote identity assurance and encryption.

How Do SSL/TLS Certificates Work?

  • When you apply for an SSL certificate and complete the authentication process, the PKI certificate authority assigns a hostname (website domain name or IP address) certificate with an SSL/TLS certificate, applies the public key to the certificate, and signatures the certificate with the certificate’s own root (or, more generally, its intermediate root) certificate.
    The browser (client) verifies the PKI certificate authority’s signature from its pre-installed root store anytime someone attempts to access a website.
  • The browser creates a session key and uses the website’s public key to encrypt it.
  • This encrypted session key hits the server on the website. By using the private key of the website, the server then decrypts it.
  • Now, for the whole session, this session key is used to encrypt and decrypt data exchanged between the browser and the server.

Code Signing Certificates/Software Signing Certificate

In order to encrypt downloaded software such as system drivers, programs, executables, and scripts, these PKI certificates are used. A certificate for code signing is bought and used by developers/publishers of applications.

How Do Code Signing Certificates Work?

  • Before issuing a code signing certificate to another individual, the CA will validate the identity of the claimant or the organisation.
  • The CA adds to the code signing certificate the public key and signatures the certificate. For the app issuer, the accompanying private key can be securely kept.
  • The software issuer can use their private key to attach a digital signature after completing a piece of software. This digital signature cannot be copied, erased, or changed by anyone.
  • The file signing certificate doesn’t encrypt the code itself, unlike an SSL certificate. Instead, along with the digital signature, it hashes the entire code.
  • When a user attempts to update the program, the PKI certificate authority’s signature is verified by their device. Then, the hash value is generated, which must fit the software hash value obtained.
  • The intact hash value indicates the program is in the same state as the software developer last created and signed it. This states that when it is in storage, it has not been tampered with or changed.

Email Signing Certificate

To secure correspondence between two email clients, an email signature certificate, also known as a secure email certificate or a S/MIME certificate, is used. It secures the data when it’s in motion and at rest by encrypting the email data before it ever reaches your email app. By allowing you to digitally sign your emails and encrypt them, this PKI certificate improves email security. It guarantees the confidentiality of the content of the email, avoids eavesdropping and offers certainty about the identity of the sender.

How Do Email Signing Certificates Work?

  • The CA will deliver an email named “Please verify your application” with a special set of guidelines when you purchase an email signing certificate.
  • The CA will give you an email signature certificate after you complete the authentication process, which you need to install on your email app.
  • Now, using your private keys, you can sign all the outgoing emails digitally. The cryptographic signature and the entirety of the email material are hashed by the email signing certificate and this hash value is encrypted.
  • When the receiver reads the text, another hash value will be created by their email client. If an email or digital signature has been tampered with in transit, the hash value of the original email will change. And the receiver will be alerted that the email’s credibility has been breached in the transit process.
  • You use the public key of the receiver to encrypt an email and they use their equivalent private key to decrypt the letter after they have obtained it.

Document Signing Certificate

The signing certificate for the paper is a way to encrypt the documents sent over the vulnerable internet. In a nutshell, these licenses verify the identity of a file creator as well as the file itself’s credibility.

How Do Document Signing Certificates Work?

  • A thorough vetting process is conducted by the PKI certificate authority to check the identity of the claimant (the person signing the document) and the organization itself. They make sure the person who signatures the contract is the company’s designated official.
  • The PKI CA mails a USB drive (a token) containing the paper signing certificate and private key to the physical address of your entity after the authentication process is completed.
  • Using this private key, the user may affix their digital signature to the paper.
  • Along with the digital signature, the paper signing certificate hashes the whole document and encrypts the hash value.
  • Another hash value is created when the receiver receives the encrypted document, which must be the same as the one preceding the document.
  • The intact hash value is evidence that, without any tempering, the text is in the same state as it was sent.
  • The digital signature consists of an RSA key of 2048 bits, which is difficult to forge. The hash value alters if anyone tampers with it, suggesting its agreement. The digital signature thus maintains the document signer’s identification.

The Role of a PKI Certificate Authority Regarding PKI Certificates

PKI certificate authorities or PKI CAs are often called the entities that are trusted to grant the PKI certificate. Most generally, however, they’re only named certificate authorities or CAs.

One of the main pillars of the PKI credential is identity assurance. The website confirms your identity as you want to use those features on a website by asking for your keys, one-time pins (OTPs), authentication questions, etc. But how do your browser (client) authenticate the website? In other words, how can you make sure that the website you’re attempting to connect with is who it wants to be, and that the knowledge isn’t being diverted to some other website’s server?

This is where a PKI credential authority falls into the frame.

The PKI certificate authority functions as a third-party mediator who is trusted in a contract by all sides. They’re responsible for issuing (and revoking) PKI digital certificates and maintaining the public keys and passwords that are used for data encryption. A PKI CA verifies the identity of the owner of the certificate, connects the public key to the PKI certificate, and uses the private key to place a digital signature on the certificate.

All the PKI certificate authorities shall adopt the certificate specification specified by X.509 specifications. They will need to strictly abide by the validation, issuance, and revocation rules defined by the Certificate Authority/Browser Forum (CA/B Forum).

The PKI credential authorities that are most accepted and commonly used include:

  • Sectigo (formerly Comodo CA)
  • DigiCert
  • GoDaddy
  • Entrust

Where Cryptographic Keys Fit into the Equation

Each website, email client, or software publisher’s server has its own unique collection of cryptographic public and private keys. The public key is open to all and is used to encrypt the data. The private key, on the other hand, is proprietary and must be kept by the PKI certificate owner securely on their computer. By holding the private key a secret, any data that’s encrypted with the public key can be decrypted with the matching private key.

These keys are made up using various types of algorithms, such as Rivest-Shamir-Adleman (RSA) or Elliptic Curve Cryptography (ECC) (ECC). The power of these keys ranges from 1024 bits to 4096 bits.

These qualifications are an important part of PKI.

A Final Word on PKI Certificates

People have some weird assumptions regarding cybersecurity, such as that small businesses or start-ups are safe online, that government departments and big companies often take high measures to save their info, etc. However, actual cybercrime figures show a completely different situation — one in which, no matter how large or small the enterprise is, it’s at risk.

Being cybersecurity cautious is a necessity that continues to develop as cybercriminals become smarter and more innovative with their assaults. PKI technology is the breakthrough in the world electronic communication. You must mount an acceptable PKI certificate on your device to protect you and your users from different forms of cyber-attacks such as man-in-the-middle attacks, email spoofing, phishing attacks, distributed denial of service (DDoS attacks), session hijacking, etc. Otherwise, a single cyber-attack is enough for a company to risk its hard-earned prestige and millions of dollars in future litigation and noncompliance fines.

Melina Richardson is a Cyber Security Enthusiast, Security Blogger, Technical Editor, Certified Ethical Hacker, Author at Cybers Guards & w-se. Previously, he worked as a security news reporter.