Engineering
How a message hops
A message with no tower to call has to be passed by hand. This is the path it takes, one radio at a time.
When you send a message over the internet, you are asking a series of machines you will never meet to forward a packet on your behalf. Nobars works the same way. The only difference is that the machines are phones, they are within about a block of you, and their owners are also at the festival.
One hop
Every phone running Nobars advertises itself over Bluetooth Low Energy in short bursts, and listens in short bursts. When two phones notice each other they open a connection just long enough to trade whatever each is carrying that the other has not seen. Then they close it again. A hop is nothing more than that: a brief, cheap handshake between two strangers' pockets.
- Your phone seals the message for its recipient. Everything after this point is an envelope nobody in the middle can open.
- It hands a copy to every peer in range, tagged with a short random id so nobody forwards the same thing twice.
- Each of those peers does the same, minus one from the hop budget, until the budget runs out or the message reaches the phone it was addressed to.
- The recipient's phone sends back a receipt the same way, which also tells the relays they can drop their copy.
Why it doesn't flood the field
The naive version of this idea melts a crowd's batteries in an afternoon: every phone shouting everything at every other phone, forever. Three rules keep it civil. Messages carry a hop budget. Every phone remembers what it has already relayed and stays quiet about it. And a phone that can hear a hundred peers relays to a handful of them, chosen for reach rather than proximity, because the peer standing next to you almost certainly heard it too.
- ~90m
- Typical single hop, outdoors
- 7
- Default hop budget
- 12h
- How long a sealed message waits to be delivered
When nobody is in range
The hard case is a message with no path at all: your friend is a mile away with nobody in between. Nobars holds it, sealed, and offers it to every phone it meets. A stranger walking from the campsite to the main gate is, briefly, the network. They carry an envelope they cannot open, hand it on, and forget it. This is the oldest kind of networking there is, and it is very hard to switch off.
There is no server in the middle because there is no middle. There is only the next phone.
