PKI & its components

      crux points:

1. PKI stands for Public Key Infrastructure.
2. A public key infrastructure (PKI) is a system that is composed of certificate authorities, certificates, software, services, and other cryptographic components, for the purpose of enabling authenticity and validation of data and entities.
3. PKI can be implemented in various hierarchical structures and can be publicly available or maintained privately by an organization.
4. As its name implies, a PKI implements asymmetric cryptography for the encryption and decryption of network data, including transactions over the Internet.

In simpler terms, just remember that PKI is a set of certificates, services etc along with essential cryptographic components used for the authenticity of data.

There are many cryptographic components that comprise PKI. Some of the important ones are-

1. Digital Signature:
   The sender creates a hashed version of the message text and then encrypts the hash itself with the users private key. The encrypted hash is attached to the message as a digital signature.
2. Digital Certificate:
   A digital certificate is an electronic document that associates credentials with a public key.
3. Certificate authority(CA):
   A CA is a server that issues digital certificates for entities and maintains the associated private/public key pair.
4. Certificate Signing Request (CSR):
   A CSR is a message sent to a CA in which an entity applies for a certificate. It typically includes information that should go into the entity's certificate, like its public key, digital signature, and other identifying information.