Public Key Infrastructure (PKI) is a framework that enables secure communication and data exchange over the internet. It uses a combination of hardware, software, policies, and standards to manage digital certificates and public-key encryption. PKI ensures that users can verify the identity of parties involved in a transaction, protecting sensitive information from unauthorized access. At the core of PKI are digital certificates, which are issued by trusted entities known as Certificate Authorities (CAs). These certificates link a public key to an individual or organization, allowing users to encrypt messages and verify signatures. This system is essential for secure online activities, such as online banking and e-commerce.