The discussion so far in this tutorial has dealt with securing computers and their contents and has been silent about securing the transmission of data among computers, using e-mail or otherwise transferring information either within a LAN directly or using an intranet or the Internet. Yet the need to extend a network to outlying parts of an organization and to customers and suppliers is very real and requires secure data transmission.
Securing data transmission means the encryption of the information being transmitted so that it cannot be read and misused by those not meant to read it. Encrypting information is probably as old as the human race and has really blossomed with the advent of computers. Data encryption has become so sophisticated that the U.S. government, worried that it won't be able to decrypt the data (can you imagine that!), hasn't until a few years ago allowed the better technology to be exported (everyone was getting it over the Internet anyway).