Add ZIP 327: Dandelion++ Transaction Propagation for Zcash P2P Nodes#1329
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This was referenced Jul 9, 2026
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…P 327) Implements Dandelion++ stem/fluff transaction propagation for Zebra to reduce IP-to-transaction correlation for network observers. Per the draft ZIP 327 (zcash/zips#1329). Core mechanism: - Per-epoch stem-peer selection (10 min base + up to 2 min jitter), `zebra-network/src/dandelion/epoch.rs`. - Per-transaction propagation state with a 30 s stem timeout, `zebra-network/src/dandelion/state.rs`. - Fail-closed stem unicast: new `Request::AdvertiseTransactionIdsToPeer` variant routed by `PeerSet::route_to_peer()` to exactly the named stem peer; if that peer isn't ready it fails with `PeerError::NoReadyPeers` rather than falling back to a different peer (which would defeat the privacy property). The gossip task then promotes the tx to fluff. - Gossip task (`zebrad/src/components/mempool/dandelion_gossip.rs`) wired into zebrad startup, replacing the immediate-flood gossip. - `MempoolChangeKind::StemAdded`: locally-submitted txs (RPC Queue) are routed through stem; peer-relayed txs go directly to fluff. Stem-phase hiding (a stem tx MUST NOT be observable before it fluffs): - P2P `MempoolTransactionIds` and `TransactionsById` (getdata) handlers filter active-stem txids. - `getrawmempool` and `getrawtransaction` RPCs filter them. - The indexer gRPC `mempool_change` stream (Zaino/lightwalletd) suppresses `StemAdded` events until the tx fluffs. - All exposure filters gate on the `Stem` state (not the elapsed timeout), so a timed-out-but-not-yet-swept tx stays hidden until the gossip task actually broadcasts it. Robustness: - `PropagationStateMap` entries are removed on Mined/Invalidated and on fluff promotion, bounding memory. - The gossip task fails open on transient PeerSet readiness errors rather than terminating. Tests: 10 unit tests (epoch, propagation state, Phase 4 filters) + 2 PeerSet routing tests. Verified end-to-end on a 3-node regtest network; see docs/dandelion-e2e-regtest.md. A companion wallet-side change (Component A: direct P2P submission) is implemented in the Android and Swift SDKs (zcash/zcash-android-wallet-sdk#2010, zcash/zcash-swift-wallet-sdk#1804).
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| ZIP: 327 | |||
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… 327/328) Adds an opt-in transaction submission path that sends transactions directly to a Zcash P2P full node via the native wire protocol instead of routing them through lightwalletd/Zaino. This closes the IP-to-transaction correlation gap at the submission boundary (a compact-block server otherwise sees the wallet IP and the transaction at the same instant). Component A of the Dandelion++ direct-submission design (ZIP 327 / ZIP 328). Default behaviour is unchanged: DandelionSubmitConfig.LightWalletD remains the default, and chain synchronisation always uses the lightwalletd endpoint regardless of this setting. - ZcashP2PSubmitter (TransactionSubmitter): DNS seeder discovery, TCP connect (5s timeout), version/verack handshake, tx message without a prior inv (unadvertised-tx convention), disconnect. java.net stdlib only. Advertises protocol version 170_150 (Zebra's NU6.2 minimum). - DandelionSubmitConfig: LightWalletD (default) or DirectP2P(network, fallbackToLightWalletD). - FallbackTransactionSubmitter: P2P primary, lwd fallback on transport error; node rejections surface immediately. - Wiring via a new dandelionSubmitConfig parameter (defaults preserve current behaviour). Related: ZIP 327 (zcash/zips#1329), ZIP 328 (zcash/zips#1330), ZcashFoundation/zebra#10928 (Component B).
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… 327/328) Adds an opt-in transaction submission path that sends transactions directly to a Zcash P2P full node via the native wire protocol instead of routing them through lightwalletd/Zaino, closing the IP-to-transaction correlation gap at the submission boundary. Component A of the Dandelion++ direct-submission design (ZIP 327 / ZIP 328). iOS equivalent of zcash/zcash-android-wallet-sdk#2010. Default behaviour unchanged: .lightWalletD remains the default and chain sync always uses the lightwalletd endpoint. - ZcashP2PSubmitter (EndpointSubmitter): DNS seeder discovery, TCP connect, version/verack handshake, tx without a prior inv (unadvertised-tx convention), disconnect. Foundation + CommonCrypto only. Advertises protocol version 170_150 (Zebra's NU6.2 minimum). - DandelionSubmitConfig enum: .lightWalletD / .directP2P; ZcashP2PNetwork. - FallbackEndpointSubmitter: P2P primary, gRPC lwd fallback. - Wiring via Dependencies.setup() and Initializer (new dandelionSubmitConfig parameter; defaults preserve current behaviour). Related: ZIP 327 (zcash/zips#1329), ZIP 328 (zcash/zips#1330), ZcashFoundation/zebra#10928 (Component B).
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… Relay Specifies the wallet-side path (Component A) for submitting transactions directly to a Zcash full node over P2P instead of via a compact-block server, using the Dandelion++ stem-phase forwarding defined in ZIP 327. Closes the IP-to-transaction correlation gap at the submission boundary: no lightwalletd/Zaino operator sees the wallet IP and the transaction together. Covers peer discovery, the version/verack handshake, the unadvertised-tx submission hint, the no-concurrent-centralised-submission rule, and fallback. Reference implementations: zcash/zcash-android-wallet-sdk#2010 and zcash/zcash-swift-wallet-sdk#1804. Co-owned network/wallet ZIP; companion to ZIP 327 (zcash#1329).
Specifies how Zcash full nodes implement Dandelion++ stem/fluff transaction propagation to reduce IP-to-transaction correlation for network observers (Component B). Covers per-epoch stem-peer selection (10 min + up to 2 min jitter), fail-closed unicast, 30 s stem timeout, stem-phase hiding from MempoolTransactionIds/getdata/getrawmempool/ getrawtransaction and the indexer stream, and fluff-phase broadcast. No new P2P message type; incremental deployment. Reference implementation: ZcashFoundation/zebra#10928. Companion wallet-side spec: ZIP 328 (zcash#1330), with SDK implementations zcash/zcash-android-wallet-sdk#2010 and zcash/zcash-swift-wallet-sdk#1804.
… number to Unassigned, update ZIP 328 cross-references to PR links
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…set ZIP number to Unassigned, update all ZIP 327 cross-references to PR zcash#1329 links
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Summary
Proposes ZIP 327, a network-layer specification for Dandelion++ stem/fluff
transaction propagation in Zcash full nodes.
Problem: Zcash transactions are currently flood-broadcast immediately,
allowing passive network observers to correlate originating IP addresses with
transactions even for shielded txs whose content is cryptographically protected.
This ZIP specifies:
inv(no new P2P message type required)mempoolP2P responses or mempool RPCsScope: Full-node relay behavior (Component B). Wallet-side direct P2P submission
(Component A) is deferred to a companion ZIP 328 (in preparation).
Reference implementation: zcashfoundation/zebra#10928 — Component B.
E2e-verified on a 3-node regtest network 2026-07-09:
txid
87ffaf8f443e9b88aa5131bd3542bfc4abd6f8c2e8852d9482de0595048fc890accepted,30 s stem window confirmed, adversary observer saw no
invduring stem phase.Full test procedure and e2e evidence are in
docs/dandelion-e2e-regtest.mdin that PR.Test plan
cargo test -p zebra-network dandelion)