Question

the code book: the science of secrecy from ancient egypt to quantum cryptography by simon singh
pretty good privacy
just as whit diffie predicted in the early 1970s, we are now entering the information age, a period in which information is the most valuable commodity. the exchange of digital information has become an integral part of our society. already, tens of millions of e - mails are sent each day, and electronic mail will soon become more popular than conventional mail. the internet, still in its infancy, has provided the infrastructure for the digital marketplace, and e - commerce is thriving. money is flowing through cyberspace, and it is estimated that every day half the worlds gross domestic product travels through the society for worldwide interbank financial telecommunications network. in the future, democracies that favor referenda will begin to have online voting, and governments will use the internet to help administer their countries, offering facilities such as online tax declarations.
however, the success of the information age depends on the ability to protect information as it flows around the world, and this relies on the power of cryptography. encryption can be seen as providing the locks and keys of the information age. for two thousand years encryption has been of importance only to governments and the military, but today it also has a role to play in facilitating business, and tomorrow ordinary people will rely on cryptography in order to protect their privacy. fortunately, just as the information age is taking off, we have access to extraordinarily strong encryption. the development of public - key cryptography, particularly the rsa cipher, has given todays cryptographers a clear advantage in their continual power struggle against cryptanalysts, and rsa encryption is therefore effectively unbreakable. most important of all, public - key cryptography has given ordinary people the power to protect their privacy.
read the excerpt from the code book
the difference between ordinary and digital mail can be illustrated by imagining that alice wants to send out invitations to her birthday party and that eve, who has not been invited, wants to know the time and place of the party. if alice uses the traditional method of posting letters, then it is very difficult for eve to intercept one of the invitations.
in comparison, eves task is made considerably easier if alice sends her invitations by e - mail.
how does the author support the claim that ordinary and digital mail are very different?
by citing statistics about both kinds of mail
by relating a personal experience of both kinds of mail
by sharing a hypothetical story as an example of the subject
by offering quotes from experts on the subject

Explanation:

The author uses the example of Alice sending party - invitations (a hypothetical story) to show the difference between ordinary and digital mail. One scenario is with traditional letter - sending and the other with e - mail, highlighting the ease of interception in the former and relative security in the latter.

Answer:

by sharing a hypothetical story as an example of the subject