Alice wants to communicate securely with Bob. In essence, this means that Alice does not want someone else to listen to the conversation, wants the information sent to Bob not to be altered on their way to him and finally she would possibly like a mechanism to prove that she had this conversation, in case, for some reason, claim he did not. We shall describe all the steps necessary to establish communication using the Certification Authority.
Alice creates a public/private key pair using a public key algorithm like RSA. Then, she creates a certificate request, which is the Certificate just prior to signing by the Certification Authority. First, the certificate request contains information about the identity of the user, such as the name, address, telephone number and e–mail address. Second, it contains her public key. Certificates can be used to authenticate not only people but also entities in general, such as a WWW server or a network device. In the latter case, the information in the Certificate would be the URL of the WWW server, the WWW Administrator details, and so on.