proposed overview structure

[nothingmuch]

each layer inherits most of the previous layer's functionality and adds additional restrictions:

• sneakernet/implicit transport honest threat model
  • bip draft dependencies:
    • concurrent & extensions - basic data format
    • scrubbing - enforcing boundary between privacy domains e.g. own signing devices and collaborative txn construction
    • hpke - optional - for embedding of out-of-band messages into psbt files
  • define net settlement / payment confirmation
    • base definition assumes out-of-band
    • can be made in-band with hpke
  • all "messages" are just PSBTs with a partial order (can't guarantee a join semilattice in general)
  • should have discussion of privacy
• interactive transaction construction w/ pluggable transports in honest threat model
  • use cases
    • multisig
    • internally segregated wallets (e.g. operational vs. customer funds)
    • collaborative batching
    • net-settlement
  • define message space to avoid in-band
  • framing format for duplex stream transports
  • broadcast
    • leader
    • clique
    • gossip
  • optional compatibility with lightning interactive-tx by bridging
• semi-honest
  • considerations for on chain structure
  • restrictions on transport
  • anonymous broadcast by relay w/ anonymous p2p transport
  • implications for liveness
• bft
  • threat model, incentives
  • coalition formation
    • ownership proofs & online key enrollment
    • listen advertisements
    • co-spend proposals
    • coalition formation proposal
    • role of aggregator in bootstrapping agreement
  • causal log structure, bft crdts = liveness in async/eventual consistency communication model (this may make sense to split, and move the non-bft component to interactive honest)
  • validity proofs
  • bft agreement
    • setchain/redebelly + weak coordinator (bootstrapped by aggregator)
    • TEE leader without redbelly? weak coordinator?
    • distributed (set union consensus)

Originally posted by @nothingmuch in #11 (comment)

[bc1cindy]

Protocol Overview

layered suite; each layer inherits the previous one and adds restrictions; fund safety never depends on peer honesty at any layer
(local validation, sign only what you accept); goals are defined by the cost function (#15), this doc is the accounting of the means.

Sneakernet / implicit transport (honest)

• no transport assumed: PSBT files exchanged by any available means
• all messages are PSBTs with a partial order; join-semilattice not guaranteed in general
• data format: concurrent PSBTs & extensions (Concurrent PSBT spec #16)
• privacy domain boundaries: scrubbing (Add scrubber bip #12)
• optional in-band messaging: hpke encrypted fragments (WIP - encrypted fragments bip outline #10)
• net settlement / payment confirmation: out-of-band by default, in-band with hpke
• privacy discussion: at this layer privacy rests entirely on the honesty assumption; problem definition in Define the on-chain privacy problems being addressed #7

Interactive construction, pluggable transports (honest)

• use cases: multisig, internally segregated wallets, collaborative batching, net settlement
• message space (avoid in-band), framing for duplex streams
• broadcast: leader / clique / gossip
• optional lightning interactive-tx compatibility by bridging
• detail doc: roles, timeouts, graph model, session parameters (Add honest overview #11)

Semi-honest

• peers comply but are not trusted with privacy
• on-chain structure considerations
• transport restrictions
• anonymous broadcast by relay over anonymous p2p transport
• liveness implications

BFT

• threat model, incentives
• coalition formation (Coalition formation #18): ownership proofs & online key enrollment, listen advertisements, co-spend proposals, coalition formation proposal, aggregator bootstrapping agreement
• causal log, bft crdts = liveness under async/eventually consistent communication; whether the non-bft component moves to interactive stays a note here, decided at detail-doc level
• validity proofs
• agreement candidates: setchain/redbelly + weak coordinator (bootstrapped by aggregator), TEE leader (with or without redbelly/weak coordinator; open), distributed set union consensus

Detailed documentation (todo index)

• message types, framing, threat models
• gossip: p2p topology w/ and w/o OHTTP service, set reconciliation
• OHTTP service: bridging, rate limiting, mailboxes, broadcast, multi-server set reconciliation

if it sounds good, happy to work on a PR!

[nothingmuch]

sorry i already called dibs on it in #11 gonna self assign to make that clear