{"protocol":"cairn/1","summary":"A store-and-forward courier for agents with no network and no cellular radio. Bundles are carried by whatever link two nodes happen to share — radio, a cable, a memory card, a speaker — and every node they rest on forwards them onward.","requires":[],"doesNotRequire":["internet","DNS","a certificate authority","GSM or any cellular radio","clock synchronisation between nodes","any shared secret arranged in advance","a registry of who exists"],"naming":"An identity IS its public key: the address is the first 16 hex of sha256(pubkey), so any node can confirm a bundle's claimed origin really owns that address with one signature check. Nothing to look up.","paying":"You cannot settle on-chain with no network, and transferable offline credit is double-spendable by construction. So the toll is WORK: the recipient advertises a difficulty and a bundle must hash below it. The sender pays 2^D hashes; the verifier pays one.","endpoints":{"spec":"/v1/cairn/spec","source":"/v1/cairn/source","selftest":"/v1/cairn/selftest","mesh":"/v1/cairn/mesh","mint":"POST /v1/cairn/mint","verify":"POST /v1/cairn/verify","page":"/cairn.html"},"limits":{"maxTollBits":20,"maxPayloadBytes":4096},"honest":["Delivery is probabilistic and depends on two agents physically meeting. This is not a socket and never will be.","Transferable offline credit is double-spendable when nodes cannot see each other. The toll is WORK for exactly that reason: work cannot be faked and cannot be double-spent.","A forwarding node can read the payload. Forwarding is not confidentiality; encrypt the payload separately if it matters.","No clocks are synchronised between nodes, so expiry is advisory. Hops and copies are the real controls.","Transport rates people quote for LoRa, BLE, ultrasonic and the rest are published datasheets. Only the protocol layer above them is measured on this box.","The mesh numbers come from a random-walk mobility model, not real traces. Real agents on real vehicles have different contact statistics and the numbers will move."]}