Discuss the role and function of a PKI

A Public Key Infrastructure (PKI) provides the framework to manage and distribute public keys and digital certificates. This enables secure electronic communication and transactions.

Its primary role is to establish and maintain a trusted environment for public-key cryptography. This supports:

• Authentication: Verifying the identity of users, devices, or services.
• Confidentiality: Encrypting data so only the intended recipient can read it.
• Integrity: Ensuring data has not been tampered with during transmission.
• Non-repudiation: Proving that a specific action, like sending a message, was performed by a particular entity, preventing denial later.

The core functions of a PKI are fulfilled through several key components:

• Certificate Authority (CA): This trusted entity issues, manages, and revokes digital certificates. A digital certificate binds a public key to an individual's or entity's identity. It contains details like the public key, the owner's identity, the CA's signature, and the certificate's validity period.
• Registration Authority (RA): The RA verifies the identity of certificate applicants on behalf of the CA. It acts as an intermediary, ensuring the legitimacy of the request before the CA issues a certificate.
• Certificate Repository: A database or directory that stores published certificates and Certificate Revocation Lists (CRLs). This allows users to retrieve certificates for validation.
• Certificate Revocation List (CRL) / Online Certificate Status Protocol (OCSP): These mechanisms check the validity of a certificate and determine if it has been revoked before its expiration date. Revocation might occur if a private key is compromised.

For example, when browsing to a website secured with HTTPS, a web browser uses the website's digital certificate, issued by a trusted CA, to verify the server's identity. This establishes a secure, encrypted connection. This process relies on the underlying PKI to ensure the certificate's authenticity and validity.