ponentially in some networked devices if the high speeds of today's networks and the plethora of communication sessions that exchange packets/frames are considered. For example, securing communications from a PC on an Ethernet does not imply the same load of computations in real time as securing hundreds or thousands of simultaneous sessions involving millions of packets entering and leaving a corporate LAN/wide area network (WAN) gate- way. Because each one of these unrelated sessions is simultaneously encrypted with different keys under different algorithms and techniques, the security-related processing load can become stagger- ing. It can easily drive the most powerful processors to their knees. In this chapter, we will show how the fundamental technologies that enable communications secu- rity in the high-speed global network are implemented inside families of powerful and specialized chips that offload the computational workload that is associated with real-time encryption and authen- tication from ordinary network processors. These chips are collectively known in the industry as secu- rity coprocessors. SECURE COMMUNICATIONS APPLICATIONS IN NETWORK PROCESSING Many communication sessions involve material that has already been secured offline prior to its trans- mission. A typical example would be encrypting the content of a computer file or e-mail message then transmitting it over an insecure link. The methods and techniques used for this purpose are also based on cryptography. As a result, they are intimately, but not completely, related to the realm described here. We will concentrate on communications security rather than information security. We will also limit our discussion to the high-speed processing environment of modern and future Downloaded from Digital Engineering Library McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. SECURITY COPROCESSORS SECURITY COPROCESSORS 361 ne