cisco exam ccna

cisco exam ccna.So anyone with a computer can use SSLOTo use SSL, you need to connect to an SSL server (an SSL-enabled web server) via the HTTPS protocol (the S in HTTPS stands for Secure) rather than the HTTP protocol. Some people also refer to SSL as Transport LayerSecurity or TLS, and to the end user, SSL represents a secure connection to the server and the right server.Even if the user enters HTTP instead of HTTPS in the browser, the web server will redirect the user's connection with the correct URL in the background. At this point, the browser will ask the web server to submit its own certificate of identity (please note that all subsequent steps are performed in the background, without user intervention). The server sends a copy of its digital certificate, also known as an SSL certificate, to the browser. Upon receipt of the certificate, the browser performs a check and determines whether it trusts the certificate. The browser uses the previously discussed method of verifying digital signatures and determines whether the certificate is valid based on the CA's signature. As soon as the certificate is trusted, the browser accesses the server public key contained in the certificate.Note: If the digital signature is invalid, or if the browser believes the certificate is invalid, it will typically pop up a window asking the user whether to continue. That's why it's important to do security training for users. Users should be trained to never accept a certificate that the browser does not trust.6.3 PKI Basics 305In most cases, the Web server will not ask the browser to prove its identity. Instead, the Web server will use some sort of user authentication mechanism (e.g., username and password authentication) to authenticate the identity of the person using the browser.After authentication is complete, the exchange of information between the browser and the server continues, as the encryption algorithm used by both and the establishment of the key used to encrypt and decrypt the data must also be determined. See later in this chapter for more information related to this. As mentioned earlier, an understanding of the relevant terminology is important in order to master encryption and VPN technology. Figure 6.6 shows the important components of encryption and VPN technology and their functions, with examples of related implementations.Figure 6-6 Basic Encryption Components6.3 PKI BasicsPublicKeyInfrastructure (PKI) is the set of identities, roles, policies, and operations used to create, enable, manage, distribute, and revoke digital certificates. PKI exists because it can be used to secure the transmission of electronic information for various applications. As readers will know, simple password authentication is not a complete authentication method. PKI provides a more rigorous method to confirm the identity of the parties involved in the communication and to authenticate the transmitted information.