What Is PKI, And How Does It Work?

What Is PKI, And How Does It Work?

Irrespective of the nature of business today, most companies use online services to store data, communicate, and manage various services. With the increase in the reliability of such online services, data theft and hacking activities are also rising.  

Hence, it has become essential for all businesses to secure their communication and online data network. Though there are many ways to secure your organization’s data, PKI has emerged as the most common security solution in recent years. PKI offers you a range of security solutions per your business needs and covers all the aspects of your business. 

But before implementing PKI, you should be well versed with the PKI and its’ working. Therefore, to help you, here is a complete guide about PKI as a security solution. 

What is PKI?

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PKI (Public Key Infrastructure) is a system of technologies, processes, and policies that enables organizations to encrypt data. With Encryption, users can securely exchange information. The best part about using this system is that all organizations can take the help of a pki as a service for analyzing and implementing a robust security system for their organization. 

PKI secures communication by one of the two methods- Authentication and Encryption. 

The most common form of Encryption used by organizations involves two keys – Public Key and Private Key. Anyone can use a public key to encrypt a message, while only one person uses the private key to decrypt messages. People, devices, and applications use these keys. The most common example of a PKI security is an SSL certificate used on websites so that the visitor knows they a visiting a secure website. Other common uses of PKI are 

  • Authenticating and encrypting email
  • Authenticating nodes to wireless
  • Authenticating VPN connections
  • Securing Public and Private based applications and services
  • Enterprise User Authentication
  • Device Authentication
  • Private Cloud-Based Authentication
  • Document/ message signing
  • Code Signing
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How does PKI work?

Image by Biljana Jovanovic from Pixabay

To understand the working of a PKI, let us first understand the two types of cryptographic algorithms and how PKI emerged. 

Symmetric Encryption

It is a simple cryptographic algorithm. In symmetric Encryption, a message typed in plain text goes through mathematical permutations to become encrypted. This encrypted message can’t be broken easily as the plain text does not always come out the same as the encrypted message. For example, the message “DDDD” would not encrypt to the same three characters. In symmetric Encryption, you need the same key to encrypt and decrypt the message. The exact key requirement carries significant risk because if the distribution channel used to share the key gets compromised, the whole system to secure the message is broken. 

Asymmetric Encryption

Asymmetric Encryption creates two different keys – a private key and a public key to encrypt messages. With asymmetric Encryption, a message also goes through mathematical permutations to get encrypted but requires a private key to decrypt and a public key to encrypt. 

Emergence of PKI

Both symmetric and asymmetric Encryption has one major challenge: How to verify the identity the person who sent the message? PKI resolves this challenge by issuing digital certificates that confirm the identity of a person, device, or application that owns a private and public key. This verification gives the user confidence as PKI assigns identities to keys. It also ensures the user that the intended recipient is the one who will actually read it and not anyone else who may be sitting as a middle man.  

Here is an example to understand PKI. Suppose you want to send secure information to your friend over the internet. The best way to secure this message is by using PKI. For this, you first need your friends’ public keys before you can send a message. This public key will enable you to encrypt the message you intend to send. Once your friend shares the public key, and the message is encrypted, your friend can decrypt and access the information using the private key. This example is the simplest form of PKI’s two-key asymmetric cryptosystem. However, other systems need to be put in place to verify the users’ identities, as this system is insufficient to secure the digital conversation. Without the additional verification system, the message can be leaked by users pretending to be original users. 

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What are the Key Elements of PKI?

Photo by Dan Nelson

To better understand the working of a PKI, you need to know what’s involved in it. A PKI includes the following key elements

1. Public Key 

It is a cryptographic key that can be distributed to the public and does not require secure storage. All messages encrypted with the public key can only be decrypted with the corresponding private key. 

2. Private Key

The users use a private key to decrypt an encrypted message using a public key. The message encrypted with the public key can only be encrypted by the matching private key, ensuring the message is only read by the approved parties. 

3. Certificate authority

The certificate authority is what makes the whole PKI system secure. They are responsible for creating digital certificates and own the policies, practices, and procedures for evaluating recipients and issuing the certificates. The certificate authority specifically determines 

  • Types of certificates issued
  • Parameters contained within the certificate
  • Vetting methods for certificate recipients
  • Security and operations procedures

4. Root Certificate Authority 

Root CA is maintained and trusted by a CA authorized to verify a person’s identity and sign the root certificate distributed to the user. 

5. Intermediate Certificate Authority

An intermediate CA is a chain between the root CA and the client certificate the user enrolls. The certificate that is generated from the intermediate CA are trusted as the root CA sign and trusts the intermediate CA. 

6. Digital Certificates

PKI ensures Encryption by issuing and managing digital certificates. This digital certificate has the following qualities 

  • Contain information about an individual
  • A trusted third-party issue it
  • It contains information that can prove its authenticity
  • Has expiration date
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Each entity is associated with a digital certificate that serves as its identity in the internet world. It is just like the passport in the real world that serves as our identity. 

How the Certificate Creation Process Works?

The certification process depends heavily on asymmetric Encryption and works as follows

  • First, a private key is created, and the corresponding public key gets computed
  • CA requests identifying attributes of the private key owner and verify it. 
  • The public key and attributes get encoded into a certificate signing request. 
  • The key owner then signs the request to prove possession of that private key. 
  • The issuing CA authority validates the request and signs the certificate with the CA’s private key. 

Anyone can use the public part of a certificate to verify that CA issued it by confirming who owns the private key used to sign the certificate. 


Public Key Infrastructure (PKI) secures our internet world by protecting sensitive data, securing communication messages, and verifying digital identities. As internet use grows for online services, this security continues to grow in importance. For businesses, in particular, introducing PKI is crucial to securing their data and channels of communication. Though implementing and continuously running the PKI is not easy, a proper understanding of your organization’s structure and PKI working will help in effective implementation.