A Certificate Authority is a trusted third party company that issues digital certificates and public-private keys as a part of chosen Public Key Infrastructure (PKI). In order to issue these certificates, a CA first consults with a registration authority (RA) such as credit card company to check whether the requester's information is legitimate. Only after the proper verification can the CA issue a certificate claiming that the organization or the individual is the one it claims to be. Having a digital certificate on a website proves the owner's identity, hence developing a trustworthy environment in business.
A certificate includes all the information about the owner, including their public key and the expiration date of the certificate.
Public Key Infrastructure
As part of a Public Key Infrastructure (PKI), a certificate authority does not issue certificates alone. PKIs issue and manage security certificates, credential verification, and public key encryption assignments. A CA verifies the credentials of the requester through a registration authority (RA) and, as a part of the PKI process, a public key is assigned for encryption. Then a SSL Certificate is issued, encrypted with a digital signature to attest the identity of the requester.
Authentication & Security
Almost all browsers present today are able to detect whether the certificate of certain website is expired or does not have the certificate signed by a known company. In such cases, a warning message usually appears on the first page designating that there is a problem with the certificate. The visitor can then opt move on to the website or to leave the page immediately.
A CA publishes its Certificate Service Policy Statement on its website. It explains the terms of business and details about the issuance of certificates. Prior to buying a digital certificate, this statement should be read in order to determine whether or not the CA is fraudulent. There are some companies that sign their own certificates, which could mean one of two things: either the company is a fraud or there is no higher authority to sign its certificate, meaning it is the top most company in this infrastructure. In this case, the validity of a company's certificate can be found out by searching the company's name.