Participant Relationship Protocol

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C04-MT: No

Rationale

In the explicitly selected CLIENT/ALL relay mode, a valid outer radio packet with an unknown channel hash can take DECODE_OPAQUE and OPAQUE_RELAY_ONLY. The receive path invokes relayOpaquePacket before module delivery. With a fresh nonzero packet ID, remaining hops, a nonlocal sender/destination and no next-hop restriction, it copies the packet, decrements hop_limit, writes the relay-node byte and sends. The sender need not know the private channel key or supply a valid payload signature for this branch. This permits an observable, protocol-shaped relay response to a chosen probe despite private-channel/STRICT protection of decoded content. Those protections remain real, but do not conceal this whole listening relay. Muting, different relay policy, packet filters, airtime/queue limits and radio failure can suppress a particular response; no universal response or measured fingerprint success rate is asserted.

Assessment method

Pinned primary-source control-flow inspection; no firmware execution or RF capture

Source context

Meshtastic firmware 8e6a88d: Router, NextHopRouter, FloodingRouter and NodeDB

Outstanding qualification

In an isolated compatible radio setup, keep CLIENT/ALL, private channel and STRICT. Inject a fresh bounded packet on a hash matching no local channel, with nonzero hop limit, broadcast destination and no next-hop preference; ensure sender is neither local nor ignored. Capture the relayed header/ciphertext and distinguish it from autonomous traffic using the chosen packet ID. Compare zero-hop, muted and invalid-signature matching-channel controls. Do not claim any payload delivery, PKI bypass or amplification measurement.

Public sources