PKI (Public Key Infrastructure)

What is PKI (Public Key Infrastructure)?

Public Key Infrastructure (PKI) is a framework that manages digital keys and certificates to enable secure communication over the internet. It provides the trust foundation that allows users, devices, and applications to verify each other’s identities and exchange data privately. PKI is the technology behind HTTPS encryption, digital signatures, and many email authentication protocols.

At its core, PKI uses two mathematically related keys: a public key and a private key. The public key can be shared openly, while the private key must remain confidential. Together, they enable encryption, decryption, and authentication processes that prove the legitimacy of a sender or system.

How PKI Works

PKI functions through a network of trusted entities known as Certificate Authorities (CAs), which issue and manage digital certificates. These certificates bind a public key to an entity (such as a person, organization, or domain) confirming that the key belongs to that entity.

The main components of a PKI system include:

• Certificate Authority (CA) – issues and revokes digital certificates
• Registration Authority (RA) – verifies identity before certificates are issued
• Certificate Repository – stores and distributes valid certificates
• Certificate Revocation List (CRL) – lists revoked or invalid certificates
• Public and Private Keys – used for encryption, signing, and verification

When a secure session is established, the sender presents a certificate signed by a trusted CA. The recipient verifies that certificate against known authorities and confirms it hasn’t been tampered with or revoked. Once validated, the public key can be used to encrypt messages or verify digital signatures.

Why PKI Is Central to Email Authentication

PKI plays a central role in securing email authentication protocols such as DKIM and S/MIME. In DKIM, for instance, a domain owner publishes a public key in DNS, while the sending server uses the matching private key to sign outgoing messages. Mail receivers use the public key to verify that the message wasn’t altered in transit and truly originates from the claimed domain.

Beyond DKIM, PKI supports encryption systems that protect message confidentiality and ensure integrity across various communication channels. Without PKI, there would be no standardized way to trust that an email signature or certificate is valid or that encrypted data hasn’t been intercepted or modified.

• DKIM uses PKI to publish and verify domain-level signatures
• S/MIME uses PKI certificates for end-to-end email encryption
• TLS certificates rely on PKI for secure mail server connections

By connecting digital identities with cryptographic assurance, PKI ensures that both human and automated systems can trust each other in every step of message delivery.

PKI and DMARCeye

DMARCeye leverages PKI-based authentication data to enhance visibility into how messages are validated across SPF, DKIM, and DMARC checks. By analyzing public keys published in DNS and correlating them with authentication outcomes, DMARCeye helps organizations detect misconfigurations, expired keys, or untrusted certificate sources.

The platform provides a clear view of key usage across your sending domains and subdomains, ensuring that DKIM and TLS configurations remain valid and secure. This continuous verification strengthens domain trust and keeps your email authentication infrastructure compliant and resilient against spoofing and tampering.

Sign up for a free trial of DMARCeye today and secure your email domain.

To learn more about DMARC and DMARC-related terms, explore the DMARCeye Glossary.