Metadata shows a great deal. For example, just by looking at the envelope, you may know if you’ve received a speeding ticket. The mailman can, too.
This is quite similar to how the internet operates now. Cryptographic seals take things a step further by being difficult to crack. Basic encryption, such as Transport Layer Security (TLS), has become a web standard in recent years. (When this is enabled, a lock icon will appear in your address bar.)
Tor circuits are based on a network of nodes
To transmit requests anonymously in the Tor network, first, create a Tor circuit. You accomplish this by sending your “sealed postcard” to a random Tor node. This address could be either residential or commercial. It could be your neighbor’s house or a large structure in another nation. This is your entry node, and all of your sealed mail will be delivered to it. This address will also be used for all future correspondence.
Your message will be forwarded by your entry node to another node, which will then forward it to another node—the exit node. The address of the intended recipient is only known to the exit node.
Tor is run entirely by volunteers
Tor might theoretically operate with physical mail, but the effort required to redirect mail and seal envelopes would be enormous. Although the Tor principle is significantly easier to implement electronically, the network continues to rely on volunteers who install Tor nodes on their servers or at home.