What is PKI, and how does it work?

What is PKI?

PKI, or public key infrastructure, is a framework that uses public key cryptography to secure online communications. PKI uses two types of cryptographic keys: a public key and a private key. Both of them ensure the confidentiality, integrity, and authenticity of communications on the internet.

PKI uses digital certificates issued by trusted organizations, usually third-party companies, called certificate authorities (CAs). A digital certificate holds the owner’s public key and other identifying information, verifies the authenticity of a user, and ensures that their public keys are valid.

Used in every web browser, PKI is one of the most commonly used and secure forms of internet encryption and includes everything necessary to create and manage public key encryption, including software, hardware, and processes essential for developing digital certificates. While PKI secures online traffic across the public internet, such as web browsing, online banking, e-commerce, and email, organizations also implement it to secure their internal communications and access to corporate networks.

How does PKI work?

To fully understand how PKI works, you need to understand its main components: keys and certificates. In the context of PKI, a key is a mathematical code that encrypts and decrypts data. At the same time, certificates are digital documents provided by CAs and contribute to the PKI system by verifying a user’s identity and who they claim to be.

PKI generates a public key and a private key first. Your public key is issued along with a digital certificate and accessible by anyone who wants to send you a message, while a private key is kept secret and is used to decrypt a received message. If you lose or someone steals your secret key, contact your CA to revoke your digital certificate and ensure that threat actors cannot use the compromised key to decrypt an encrypted message.

A digital certificate, which contains the owner’s identity information, is primarily used by the owner to prove their identity, and it is typically sent during the initial handshake process. Then the recipient uses the CA’s public key to verify the certificate’s digital signature. A digital signature ensures the certificate’s integrity and confirms that a trusted CA issued it.

This process is called authentication and establishes trust between the parties. Then the TLS and SSL protocols secure encrypted communication channels, so only the intended recipient can read the message, and an unauthorized party cannot intercept the communication.

It is an essential technology that ensures a secure exchange of information over the internet, and understanding how it works is crucial in maintaining online privacy and security.

What is PKI used for?

Individuals and companies use PKI to secure communication over the internet. The technology behind PKI, including private and public keys, encrypts data transmission, authenticates access to data, and provides a secure method of exchanging digital information online. Organizations and individuals use PKI to ensure the confidentiality of the information exchanged in various applications, such as secure web browsing, email encryption, digital signatures, and online transactions.

What are PKI certificates?

PKI certificates are digital documents taking the leading role in PKI technology. They’re used to authenticate and secure electronic communications. Here are some key points about PKI certificates:

• Digital identity. PKI certificates issue digital identities to individuals or organizations. The certificates hold the essential entity’s information, such as name, public key, serial number, and expiration date.
• Certificates include public and private cryptographic keys. The public key can be shared with anyone, while the private key is only accessible by the certificate owner.
• Certificate authority. Certificate authorities are trusted third-party organizations that verify the identity of the certificate requester and issue certificates.
• Authentication. One of the primary responsibilities of PKI certificates is to authenticate access to network systems. When a user or a device requests access or sends a message, the recipient can verify their identity by checking the requester’s digital signature and the CA’s trust chain.
• Secure communication. Data encryption and digital signatures are another responsibility of PKI certification. Encryption uses the recipient’s public key to secure data, ensuring only authorized recipients can decrypt the message or information. Meanwhile, the certificate holder’s private key creates a unique digital signature providing integrity.
• Certificate revocation. CA-issued certificates have an expiration date, but if the certificate is compromised, the CA can revoke it before the date to prevent cybercriminals from using the certificate illegally.

PKI Components

PKI is a complex system responsible for securely exchanging digital information online. It consists of several key components that harmonize to establish trust between data sender and receiver, authenticate entities, and protect sensitive information. Let’s look at some essential PKI components that ensure seamless and confidential digital communication.

Public Key

When implementing PKI, each individual or device gets a key pair: public and private, creating asymmetric cryptography. A user’s public key can be freely shared and accessible to anyone who wants to communicate securely with the key holder or recipient. The public key is included in its owner’s digital certificate and is used by other parties to encrypt data addressed to the recipient. A public key is also important in verifying identity with a digital signature created using the key holder’s private key. The public key enables authentication within the PKI framework and is one of the main components in securing online communication.

Private key

Another critical component of PKI and the counterpart to the public key is the private key. The private key always remains confidential and secure, accessible only by the entity it was issued to. It is used in digital signing, sensitive data encryption, and decrypting data that the public key has encrypted. A user must keep the private key a secret because its compromise could lead to unauthorized access, data breaches, and jeopardize the whole network or individual PKI system.

Certificate authority (CA)

Behind every individual or company’s PKI infrastructure lies the CAs, trusted third-party entities issuing, managing, and revoking digital certificates. They take the leading role in securing digital communications and verifying the identity of PKI certificate holders when accessing encrypted data and in digital signing processes. CAs apply a robust verification process to ensure individual or device authenticity when providing access to systems. Therefore, individuals and organizations can have complete confidence in the authenticity and security of the certificates issued by the CA.

Registration authority (RA)

RA is an intermediate between PKI certificate requesters and the CA and plays a vital role in identity verification. It collects necessary information from the certificate applicants and generates certificate signing requests (CSR) in their names. RA is an initial point of contact that facilitates the certificate issuing process by gathering data from a requester and forwarding it to CA. RA helps to ensure a seamless and efficient certification process.

Certificate revocation list (CRL)

Sometimes certificates need to be revoked before the expiration dates, such as in cases where they are compromised or invalid. CRL is a mechanism that informs users and related parties about revoked certificates. CRLs revoke digital certificates and are supervised by the CAs. They contain serial numbers and other identifying information of no longer valid certificates.

Advantages and disadvantages of PKI

PKI has advantages and disadvantages. Here are some of them:

Advantages of PKI

Here are the main advantages of implementing PKI into your cybersecurity infrastructure:

• Security. PKI uses asymmetric cryptography to ensure digital communication security. It safeguards the confidentiality and authenticity of digital information through data encryption and digital signatures.
• Authentication. PKI is a cornerstone of internal authentication processes. It verifies user or device identity through digital certificates, significantly reducing the risk of identity theft, impersonation, and unauthorized access.
• Non-repudiation. PKI carefully monitors the use of certificates, meaning a user cannot deny their involvement in a specific transaction or communication. A public key validates the digital signature assigned to it, disclosing the sender’s identity and ensuring reliability.
• Scalability. PKI is a powerful technology that can handle many customers, including individual users and large-scale enterprises with extensive systems and internal networks. PKI supports large projects while ensuring the efficient security of digital communications.

Disadvantages of PKI

Having listed all the benefits, here are some of the downsides of PKI infrastructure:

• Complexity. Deployment and maintenance of an on-site PKI system can be complex and costly regarding resources. Various components, including CAs, CRLs, and key management, require financial expenses, skilled personnel, and suitable infrastructure to keep the system running as the company grows and internal systems change.
• Cost. Implementing and managing a PKI technology can be costly. Companies need to invest in hardware, software, and qualified personnel to establish a smooth digital communication infrastructure and keep data safe from prying eyes. Moreover, acquiring digital certificates from trusted CAs may involve recurring costs for organizations.
• Certificate revocation. Every digital certificate has an expiration date. However, CAs can revoke the PKI certificate’s validity if a private key is compromised or a user’s privileges change. It may be challenging to maintain up-to-date CRLs, and a failure to do so may result in data breaches.
• Dependency on CAs. The smooth operation of the PKI system and the security of the data depend heavily on the trustworthiness of the CAs. If the CA’s functionality is compromised or it issues compromised digital certificates, this can affect the entire organization’s PKI system. Therefore, entities must regularly monitor and audit their PKI system to prevent such system disruptions.

PKI role in cybersecurity

Secure digital communication and protection of sensitive data are principal in today’s digital landscape. PKI is a cornerstone of an organization’s cybersecurity infrastructure and is crucial in safeguarding confidential data. Let’s explore how important PKI is in protecting our digital assets:

• Secure communication. Feeling safe when communicating online is invaluable. PKI ensures your peace of mind. It uses powerful encryption algorithms to ensure secure public or internal company network communications. It encrypts data, ensures the confidentiality of shared information, and guarantees that only authorized users can access it.
• Authentication. Access authentication may be one of the main tools to safeguard your digital assets from bad actors. One of PKI’s core purposes is to verify the identity of individuals or devices involved in communication. Digital certificates issued by trusted CAs guarantee transparency in the communication process and protect against unauthorized access.
• Data integrity. PKI ensures data accuracy and detects unauthorized modifications or forgery through digital signatures and private keys.
• Non-repudiation. PKI ensures that the sender or receiver of a message cannot deny being involved in the communication. Digital signatures identify the sender and leave no room for misrepresentation or deceit.
• Certificates and keys. PKI’s framework is based on cryptographic keys and digital certificates issued by third-party CAs, vital in issuing digital certificates and managing keys. These components are integral to authentication processes and essential for maintaining system security.
• Securing transactions. PKI is a fundamental tool that secures electronic transactions, including those made through e-commerce, online banking, and digital signatures. It protects sensitive data and ensures the authenticity of transactions by implementing the necessary security measures.

PKI plays an important role in individual and organizational cybersecurity. Its robust algorithms are calibrated to ensure safe online transactions, authentication, data integrity, and safe communications, which are vital for transparent digital interactions. While the digital landscape expands, PKI continues to play an essential role in cybersecurity and is an indispensable companion to confidentiality and authenticity.