ABSTRACT
Data that is generated by the user (a human or an application) will be prepared to be transmitted to the destination machine. This procedure follows a number of steps, including enclosing the user’s data in a digital envelope that contains all the information needed to allow the correct communication of the data from the source machine and application to the destination machine and application.The enclosure of the user’s data is made by the addition of successive digital envelopes. To better illustrate this idea, let us consider an example to support some of the claims we will make later in this chapter. Suppose you are on vacation in a place without computers or phones of any kind, the only means of communication being regular mail and the only means of recording a message being plain old paper and pencil. You need to warn your colleague of a meeting you forgot to add to his/her calendar. You could do it like this: You could write the message on a small piece of paper and send it by regular mail to your company, asking the secretary to place this piece of paper in a place where your colleague would see it when he/she arrives. The message inside the envelope could look like the one shown in Fig. 10.2.
