Both Kerberos and the Public Key Infrastructure are integral parts of the Windows Server 2003 operating system. Kerberos provides domainwide authentication to any service throughout the Windows Server 2003 domain and offers compatibility with many other operating systems. PKI enables secure communication, data storage, and universal authentication throughout Internet and extranet environments. These technologies lay the groundwork for IPSec, VPNs, secure Web transactions, e-mail communications, and centralized user account management.