A variety of identification systems in use on the Web today are designed to provide the same sort of assurance in cyberspace that they offer in the real world. The simplest of the systems are based on usernames and passwords; others are based on special-purpose hardware that can measure unique distinguishing characteristics of different human beings. Finally, there are systems that are based on cryptography, relying on the public key cryptography techniques introduced in earlier chapters.
This chapter presents a survey of the various digital technologies that are available to identify people on and off the Internet. Chapter 7 describes the use of digital certificates and their use in the public key infrastructure (PKI).
Fly to San Francisco International Airport, flash two pieces of plastic, and you can drive away with a brand new car worth more than $20,000. The only assurance the car rental agency has that you will return its automobile is your word—and the knowledge that if you break your word, they can destroy your credit rating and possibly have you thrown in jail.
Your word wouldn’t mean much to the rental agency if they didn’t know who you are. It’s your driver’s license and credit card, combined with a worldwide computer network, that allows the rental agency to determine in seconds if your credit card has been reported stolen, and that gives the firm and its insurance ...