Assume computers and the internet do not exist, and people continue to communicate by what we now refer to as “conventional mail.”
Assume you wish to buy a book. How did you do that without leaving your house? You may seek up a publishing house’s address in the yellow pages and send them a postcard.
You might express your desire to purchase a book you enjoy on that card, and you could give your own address so the publisher knows where to send it.
Everyone along the delivery route can see what everyone wants to read, which is a problem. They can copy everything or simply keep track of who requested what.
Envelopes keep the contents safe
Requests could be put inside sealed envelopes for further security. Because these cryptographic seals are impossible to crack without breaking them, the post office could only keep track of what was delivered where without knowing what was inside the envelopes.
The metadata refers to information such as the size and weight of the envelope, as well as the sender and recipient’s names.
