Hybrid Transport & Avalanche-Efficient Dissemination

[KarimHassan]

BitChat is fully offline and peer-to-peer. Devices connect over Bluetooth, and messages spread by gossiping with a TTL. That works well for local meshes, but we may run into problems when:

• Devices are too far apart (no mesh path).
• The mesh is dense, and rebroadcasting wastes battery.

I think it can be solved by having:

• Hybrid mode with gateways (optional internet/backhaul).
• Avalanche-style spreading (smarter gossip + retry logic).

This can allow Messages to travel across internet relays when meshes don’t connect, with End-to-end Noise encryption using nip-17 and it save resources

flowchart LR
  %% ========== CLUSTERS ==========
  subgraph L["Local Mesh (Origin Side)"]
    A["Peer A<br/>origin"]
    B["Peer B"]
    C["Peer C"]
    D["Peer D"]
    E["Peer E"]
    F["Peer F"]
    G["Peer G<br/>Internet-capable"]
  end

  subgraph RZ["Remote Mesh (Destination Side)"]
    H["Peer H"]
    I["Peer I"]
    J["Peer J"]
    K["Peer K"]
    R["Peer R<br/>Recipient"]
  end

  subgraph NET["Nostr Relay"]
    NR["Nostr Relay<br/>(NIP-17 ephemeral)"]
  end

  %% ========== ORIGIN AVALANCHE ==========
  A -- gossip/TTL --> B
  A -- gossip/TTL --> C

  B -- gossip/TTL --> D
  B -- gossip/TTL --> E

  C -- gossip/TTL --> F
  C -- gossip/TTL --> G

  %% Internet bridge (STOP #1 after upload)
  G -- sealed Noise envelope --> NR

  %% Local suppression after reaching relay (STOP #1)
  D -. suppression after STOP #1 .-x D
  E -. suppression after STOP #1 .-x E
  F -. suppression after STOP #1 .-x F
  C -. suppression after STOP #1 .-x C
  B -. suppression after STOP #1 .-x B
  A -. suppression after STOP #1 .-x A

  %% Remote side pulls from relay and re-gossips
  NR -- opaque event --> H
  NR -- opaque event --> I

  H -- gossip/TTL --> J
  I -- gossip/TTL --> K

  %% Delivery to recipient (STOP #2 after Ack)
  J -- gossip/TTL --> R
  K -- gossip/TTL --> R

  %% ========== ACK + STOP PROPAGATION (remote) ==========
  R -. DeliveryAck .-> H
  R -. DeliveryAck .-> I
  R -. DeliveryAck .-> NR
  R -. DeliveryAck .-> J
  R -. DeliveryAck .-> K

  %% "STOP" callouts as separate nodes (flowcharts don't support note blocks)
  S1[[STOP #1<br/>Internet peer uploads sealed ciphertext to relay.<br/>Origin-side avalanche suppresses.]]
  S2[[STOP #2<br/>Recipient received & acked.<br/>Remote avalanche suppresses.]]

  G -.-> S1
  R -.-> S2

  %% Visual classes
  classDef relay fill:#f3f9ff,stroke:#3b82f6,color:#1f2937,stroke-width:2px;
  classDef internet fill:#ecfdf5,stroke:#10b981,color:#065f46,stroke-width:2px;
  classDef recipient fill:#fff7e6,stroke:#f59e0b,color:#92400e,stroke-width:2px;
  classDef origin fill:#eef2ff,stroke:#6366f1,color:#111827,stroke-width:2px;
  classDef stop fill:#ffe9e9,stroke:#e74c3c,color:#c0392b,stroke-width:2px;

  class NR relay;
  class G internet;
  class A origin;
  class R recipient;
  class S1,S2 stop;

Loading

sequenceDiagram
  autonumber
  participant A as Peer A (origin)
  participant B as Peer B
  participant C as Peer C
  participant G as Peer G (internet)
  participant NR as Nostr Relay (NIP-17)
  participant H as Peer H (remote)
  participant I as Peer I (remote)
  participant J as Peer J (remote)
  participant K as Peer K (remote)
  participant R as Peer R (recipient)

  rect rgb(230,245,255)
  Note over A,G: Local avalanche (origin side)
  A->>B: Gossip (Noise ciphertext, TTL)
  A->>C: Gossip (Noise ciphertext, TTL)
  C->>G: Gossip (Noise ciphertext, TTL)
  end

  rect rgb(235,255,245)
  Note over G,NR: STOP #1 — relay reached
  G->>NR: Publish sealed envelope (NIP-17 ephemeral)
  Note right of NR: Relay does NOT see plaintext
  Note over A,G: Origin-side suppression kicks in after upload
  B-->>B: Heard again? → suppress
  C-->>C: Heard again? → suppress
  end

  rect rgb(255,245,230)
  Note over NR,I: Remote mesh resume
  NR-->>H: Ephemeral event (opaque)
  NR-->>I: Ephemeral event (opaque)
  H->>J: Gossip forward (TTL--)
  I->>K: Gossip forward (TTL--)
  J->>R: Deliver to recipient
  K-->>R: Possible duplicate (suppressed)
  end

  rect rgb(255,238,238)
  Note over R: STOP #2 — recipient received
  R-->>H: DeliveryAck
  R-->>I: DeliveryAck
  R-->>NR: (optional) Receipt signal
  Note over H,K: Remote-side suppression after Ack
  end

Loading