The Function and Components of PKI

The Function of the PKI
The primary function of the PKI is to address the need for privacy throughout a network. For the administrator, there are many areas that need to be secured. Internal and external authentication, encryption of stored and transmitted files, and e-mail privacy are just a few examples. The infrastructure that Windows Server 2008 provides links many different public key technologies in order to give the IT administrator the power necessary to maintain a secure network.

Most of the functionality of a Windows Server 2008-based PKI comes from a few crucial components, which are described in this chapter. Although there are several thirdparty vendors such as VeriSign ( that offer similar technologies and components, using Windows Server 2008 can be a less costly and easier to implement option—especially for small and medium-sized companies.

Components of PKI
In today’s network environments, key pairs are used in a variety of different functions.
This series will likely cover topics such as virtual private networks (VPNs), digital signatures, access control (SSH), secure e-mail (PGP—mentioned already—and S/MIME), and secure Web access (Secure Sockets Layer, or SSL). Although these technologies are varied in purpose and use, each includes an implementation of PKI for managing trusted communications between a host and a client.

While PKI exists at some level within the innards of several types of communications technologies, its form can change from implementation to implementation. As such, the components necessary for a successful implementation can vary depending on the requirements, but in public key cryptography there is always:
• A private key
• A public key
• A trusted third party (TTP)

Since a public key must be associated with the name of its owner, a data structure known as a public key certificate is used. The certificate typically contains the owner’s name, their public key and e-mail address, validity dates for the certificate, the location of revocation information, the location of the issuer’s policies, and possibly other affiliate information that identifies the certificate issuer with an organization such as an employer or other institution.

In most cases, the private and public keys are simply referred to as the private and public key certificates, and the trusted third party is commonly known as the certificate authority (CA). The certificate authority is the resource that must be available to both the holder of the private key and the holder of the public key. Entire hierarchies can exist within a public key infrastructure to support the use of multiple certificate authorities.

In addition to certificate authorities and the public and private key certificates they publish, there are a collection of components and functions associated with the management of the infrastructure. As such, a list of typical components required for a functional public key infrastructure would include but not be limited to the following:

• Digital certificates
• Certification authorities
• Certificate enrollment
• Certificate revocation
• Encryption/cryptography services

Although we have already covered digital certificates and certificate authorities at a high level, it will be well worth our time to revisit these topics. In the sections to follow, we will explore each of the aforementioned topics in greater detail.

Source of Information : Syngress The Best Damn Windows Server 2008 Book Period 2nd Edition

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