Public Key Infrastructure (PKI)

Introduction

Public Key Infrastructure (PKI) is a set of roles, policies, and procedures needed to create, manage, distribute, use, store, and revoke digital certificatesDigital Certificates and manage public-key encryption. The purpose of a PKI is to facilitate the secure electronic transfer of information for a range of network activities such as e-commerce, internet banking and confidential email.

Overview

A PKI is a framework that enables various internet activities and transactions to be conducted securely. The infrastructure involves the use of a public and private cryptographic key pair that is obtained and shared through a trusted authority. The key pair is used to encrypt and decrypt content. PKI provides a digital certificate that can identify an individual or an organization and directory services that can store and, when necessary, revoke the certificates.

Components of PKI

A PKI consists of several core components:

Certificate Authority (CA): This is the trusted central authority that issues and revokes digital certificates. A CA verifies the identity of the certificate holder and provides assurance to others that the holder is who they claim to be.

Registration Authority (RA): An RA is responsible for accepting requests for digital certificates and authenticating the entity making the request.

Central Directory: This is a secure location where keys are stored. The central directory ensures keys are accessible to multiple applications if needed.

Certificate Management System: This system manages the creation, storage, distribution and revocation of certificates.

Certificate Policy: This is a document that outlines the different entities of a PKI, their roles and their duties.

A photograph of a secure server room, symbolizing the infrastructure of a PKI.

Working of PKI

PKI works by using two types of cryptographic keys: a public key and a private key. The public key is available to any user that connects with the website. The private key is a unique key generated when a connection is made, and it is kept secret. When a user connects to a website secured with SSL, the website sends a copy of its SSL certificateSSL Certificates along with the public key. The user's device uses this to encrypt data and sends it back to the source server where it is decrypted using the private key.

Applications of PKI

PKI has a wide range of applications in modern digital communication and transactions. Some of the notable applications include:

Secure Email: PKI provides the ability to exchange information securely over email by encrypting the data and providing a digital signature.

Secure Electronic Transactions (SET): SET is a system for ensuring the security of financial transactions on the internet. It uses a PKI to secure credit card transactions.

Virtual Private Networks (VPN): PKI is used in VPNs to secure communication over public networks.

Secure Socket Layer (SSL) and Transport Layer Security (TLS): These are cryptographic protocols designed to provide secure communication over a network. PKI is used to issue, manage and revoke the digital certificates used in these protocols.

Code Signing: PKI is used to digitally sign software applications and scripts, which verifies the author of the software and guarantees that it has not been altered or corrupted since it was signed.

Security Considerations

While PKI provides a high level of security, it is not without its challenges. Some of the key security considerations include:

Key Management: The secure management of the private key is critical. If the private key is lost, the corresponding certificate becomes useless. If the private key is stolen, this could allow an attacker to decrypt data.

Certificate Expiry: Certificates have a set validity period and must be renewed regularly. Failure to renew a certificate can lead to a loss of trust in the certificate.

Revocation: If a certificate is compromised, it must be revoked. However, the revocation process can be complex and time-consuming.