Comment by shagie

The internet is a marketplace with a million vendors, each with their own stall.

In order to sell something in the market, you need to prove that you are who you say you are. There are about 200 trusted clerks whose job it is to check your papers and verify your identity. Once they're satisfied, they stamp your papers with an intricate stamp designed by the finest cryptographers.

Anyone seeing that stamp knows that a trusted clerk has checked your identity and approved your papers. Most people don't examine the stamp closely. They simply recognize it as belonging to one of the trusted clerks and accept it.

One of these clerks, however, instead of commissioning an intricate stamp from a master cryptographer, bought an ordinary rubber stamp from an office supply store.

One day, a particularly paranoid cryptographer was examining the stamps used throughout the market and noticed something peculiar about one of them. It wasn't intricate at all. In fact, it was so simple that anybody with a few dollars and a trip to the office supply store could make an identical stamp.

The clerk's job wasn't merely to stamp papers. The clerk was supposed to check that everything written on them was true before applying the stamp.

But now anyone could write whatever they wanted on their own papers and stamp them. The resulting documents would look exactly like ones that had been carefully checked and approved by the clerk.

A robber could write "thebank.com" on their papers, stamp them with the office supply rubber stamp, and present themselves as thebank.com. If they could get a customer to come to their stall instead of the real bank's, the customer would have no reason to suspect anything was wrong.

After all, the papers had the stamp of a trusted clerk. And everyone who trusted that clerk's stamp would believe them.