What Is Public Key Infrastructure (PKI) and How Does It Work?

By John Adebimitan

A solid internet security and privacy program could be what you need to safeguard against unauthorized access to sensitive information. It could also just be what you need to survive breaching attempts by cybercriminals.

Here’s where encryption technologies like PKI come in. They help encode data into an unreadable format, ensuring that only authorized parties can decipher it.

In today’s guide, you will learn about what PKI really is. It will also give you a walkthrough on how it works and why it is important, among other basics, including the types of open-source PKI certificates. So, keep reading!

What is PKI?

Public Key Infrastructure (PKI) encompasses the technology and processes that form an encryption framework, securing and verifying digital communications. PKI uses cryptographic public keys linked to a digital certificate that validates the sender’s identity.

These certificates are issued by a trusted Certificate Authority (CA) and function as digital passports to ensure authenticity. PKI safeguards and authenticates communications.

These processes help shield against tampering during transit. They also help maintain confidentiality and trust. Here are the key components of PKI;

  • Registration Authority (RA): The Registration Authority (RA) verifies the identity of users or devices seeking a digital certificate. Essentially, the RA acts as an intermediary to ensure that only legitimate entities receive certificates.
  • Certificate Authority (CA): The Certificate Authority (CA) is a trusted entity responsible for issuing, storing, and signing digital certificates. The CA uses its own private key to sign the digital certificate. It then makes the public key available upon request. This signature confirms the validity of the certificate.
  • Central Directory: The Central Directory acts as a secure repository for cryptographic keys. It indexes and stores these keys. This ensures that they remain confidential and protected from unauthorized access.
  • Certificate Database: The Certificate Database is the vault of digital certificates and their associated metadata. It records all the important details. Key among these details include the certificate’s validity period.
  • Certificate Policy: The Certificate Policy sets out the guidelines and procedures that govern the PKI. It defines the rules for certificate issuance, management, and usage.
  • Certificate Management System: The Certificate Management System oversees the issuance and access of certificates. It doesn’t only ensure that certificates are delivered to the right entities. It also sees to it that access is granted only to authorized parties.

Why Is PKI Important?

The Public Key Infrastructure holds key importance in high-security scenarios. It establishes trust through digital signatures and cryptographic keys. 

This helps ensure security in various applications. Imagine sending data from one Mac device to another—PKI ensures you’re communicating with the authentic server. Not a counterfeit.

Digital certificates vouch for the identity of both parties by confirming that a specific public key belongs to a certain entity. Some of the use cases of PKI include; safeguarding emails and web transactions, signing software, encrypting and decrypting files, and authenticating with smart cards.

Understanding How PKI Works

PKI, or Public Key Infrastructure, operates on the foundation of certificates and keys. A key, a lengthy number, encrypts data.

In a simple analogy, it’s like replacing each letter in a message with the next one. PKI, however, uses complex mathematical concepts.

Unlike a single key, PKI involves two: a public and a private key. The public key is accessible to anyone.

It encrypts messages sent to you. The private key, known only to you, decrypts these messages. The keys’ connection is complex, which makes it extremely difficult to deduce the private key from the public one.

What Are PKI Certificates?

Simply put, a PKI Certificate is a digital certificate used for the authentication of users, servers, or devices online. They work more like giving entities permission to exchange PKI keys.

They contain a unique identity which is vital for participating in PKI-encrypted data transactions. A certificate holds the public key, which enables its sharing between parties, along with a trusted attestation confirming the entity’s identity.

The Certificate Authority (CA) issues these certificates. A Registration Authority (RA) processes signing requests to facilitate the issuance and renewal for various entities.

Certificates find their home in a certificate database on the CA server. Usually, a local copy is stored on the device or computer for communication.

This storage is referred to as the certificate store. Certificate policy is another crucial aspect, defining roles and entities within a PKI interaction. It’s published within the PKI perimeter, and in X.509 certificates, a link may be included.

Why is PKI used?

Public Key Infrastructure (PKI) is crucial for secure digital communication. It is used because it helps ensure confidentiality and authenticity in confidential communications.

PKI is also used in the verification of the identity of parties involved to safeguard against impersonation. This trusted system is fundamental for secure online operations. Key use cases of PKI include;

  • Hypertext Transfer Protocol Secure (HTTPS): PKI certificates in HTTPS encrypt data exchanged between users and websites. To enable HTTPS on your websites, you may only need to acquire cheap SSL certificates. You will easily find cheap SSL from a leading certificate authority (CA) like Sectigo, Comodo, DigiCert, etc. If SSL configured correctly, these certificates can help prevent unauthorized access, fraudulent activities, and man-in-the-middle attacks. 
  • Secure Shell (SSH): SSH uses X.509 certificates from PKI to authenticate computers and users. These certificates confirm the identity of the parties involved to improve the security of remote connections. SSH ensures that only authorized users gain access.
  • Signing and Encrypting Emails: PKI certificates facilitate the encryption and digital signing of emails to ensure confidentiality and authenticity.

Types of Open-source PKI

Just as it sounds, open-source PKI is CA software open for public use, modification, and distribution. It serves as a private CA for internal trust within a business or for publicly trusted SSL/TLS certificates.

This accessibility encourages collaborative development and customization so businesses can have more control over their security infrastructure. Here are some examples of open-source PKI;

  • EJBCA Enterprise: Developed in Java, it’s an enterprise-grade CA implementation suitable for both internal use and setting up CA as a service.
  • OpenSSL: This is a commercial-grade toolkit developed in C. It’s widely included in major Linux distributions and can be used to PKI-enable applications or construct a basic CA.
  • CFSSL: Cloudflare’s PKI/SSL toolkit is designed for tasks like signing, verifying, and bundling TLS certificates. It’s also handy for building customized TLS PKI tools.
  • XiPKI: This Java-based CA and OCSP responder boasts high performance and scalability. It also supports SHA-3.
  • Dogtag Certificate System: An enterprise-class CA, it provides comprehensive support for all aspects of certificate lifecycle management.

In Closing

PKI is a sophisticated framework for safeguarding digital communications. Its role in securing sensitive information and enabling trust in online interactions is indispensable.

So, embracing PKI is not only a technological necessity. It is also a safeguard for businesses and individuals alike.

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