PKI is the underlying cryptography system that enables users or computers that have never been in trusted communication before to validate themselves by referencing an association to a trusted third party (TTP). Once this verification is complete, the users and computers can now securely send messages, receive messages, and engage in transactions that include the interchange of data.
PKI is used in both private networks (intranets) and on the World Wide Web (the Internet). It is actually the latter, the Internet, that has driven the need for better methods for verifying credentials and authenticating users. Consider the vast number of transactions that take place every day over the internet—from banking to shopping to accessing databases and sending messages or files. Each of these transactions involves at least two parties. The problem lies in the verification of who those parties are and the choice of whether to trust them with your credentials and information.
The PKI verification process is based on the use of keys, unique bits of data that serve one purpose: identifying the owner of the key. Every user of PKI actually generates or receives two types of keys: a public key and a private key. The two are actually connected and are referred to as a key pair. As the name suggests, the public key is made openly available to the public while the private key is limited to the actual owner of the key pair. Through the use of these keys, messages can be encrypted and decrypted, allowing data to be exchanged securely.
The use of PKI on the World Wide Web is so pervasive that it is likely that every Internet user has used it without even being aware of it. However, PKI is not simply limited to the Web; applications such as Pretty Good Privacy (PGP) also leverage the basis of PKI technology for e-mail protection; FTP over SSL/TLS uses PKI, and many other protocols have the ability to manage the verification of identities through the use of key-based technology. Companies such as VeriSign and Entrust exist as trusted third-party vendors, enabling a world of online users who are strangers to find a common point of reference for establishing confidentiality, message integrity, and user authentication. Literally millions of secured online transactions take place every day leveraging their services within a public key infrastructure.
Technology uses aside, PKI fundamentally addresses relational matters within communications. Specifically, PKI seeks to provide solutions for the following:
• Proper authentication
By using the core PKI elements of public key cryptography, digital signatures, and certificates, all these equally important goals can be met successfully. The good news is that the majority of the work involved in implementing these elements under Windows Server 2008 is taken care of automatically by the operating system and is done behind the scenes.
The first goal, proper authentication, means that you can be highly certain that an entity such as a user or a computer is indeed the entity he, she, or it is claiming to be. Think of a bank. If you wanted to cash a large check, the teller will more than likely ask for some identification. If you present the teller with a driver’s license and the picture on it matches your face, the teller can then be highly certain that you are that person—that is, if the teller trusts the validity of the license itself. Because the driver’s license is issued by a government agency—a trusted third party—the teller is more likely to accept it as valid proof of your identity than if you presented an employee ID card issued by a small company that the teller has never heard of. As you can see, trust and authentication work hand in hand.
When transferring data across a network, confidentiality ensures that the data cannot be viewed and understood by any third party. The data might be anything from an e-mail message to a database of social security numbers. In the last 20 years, more effort has been spent trying to achieve this goal (data confidentiality) than perhaps all the others combined. In fact, the entire scientific field of cryptology is devoted to ensuring confidentiality (as well as all the other PKI goals).
As important as confidentiality is, however, the importance of network data integrity should not be underestimated. Consider the extreme implications of a patient’s medical records being intercepted during transmission and then maliciously or accidentally altered before being sent on to their destination. Integrity gives confidence to a recipient that data has arrived in its original form and hasn’t been changed or edited.
Finally we come to nonrepudiation. A bit more obscure than the other goals, nonrepudiation allows you to prove that a particular entity sent a particular piece of data. It is impossible for the entity to deny having sent it. It then becomes extremely difficult for an attacker to masquerade as a legitimate user and then send malevolent data across the network. Nonrepudiation is related to, but separate from authentication.
Source of Information : Syngress The Best Damn Windows Server 2008 Book Period 2nd Edition