Privacy in everyday life is nothing new. When you buy something at the grocery, no one is going to ask you for some form of ID, and when you send a snail-mail letter, the Post Office doesn't check if the return address is valid. And who wouldn't be very upset if they found out that the mailman had been reading their mail?

However, on the Internet privacy is regarded a lot less normal. Messages are sent as clear text, so that everyone with a little knowledge can read them, and there is no built-in way to prevent someone else from forging something in your name, so that you can't prove it wasn't you. Even worse, data on your own hard disk can be examined by everyone who has access to your office or room.