Draft: Add PIR-based spendability checking and witness fetching#15
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Orchard notes are not spendable until the shard-tree scanner catches up to the block that contains them. For wallets restoring from seed or lagging behind the chain tip, this can mean waiting hours before funds are usable. Private Information Retrieval lets the wallet query a server to (1) learn which notes have been spent and (2) obtain note commitment tree witnesses — all without revealing which notes belong to the wallet. This makes funds spendable before the scanner completes, dramatically improving the restore experience. Made-with: Cursor
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This was referenced Apr 10, 2026
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Apr 10, 2026
| spendingKey: spendingKey | ||
| ) | ||
| } catch { | ||
| logger.info("[PIR-DEBUG] createProposedTransactions: status=\(isSyncing), usePIRWitnesses=\(proposal.pirWitnessConfig?.usePIRWitnesses ?? false), pirServerURL=\(proposal.pirWitnessConfig?.serverURL ?? "nil")") |
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Note: logs are intentionally left for now for ease of retesting. Tracking to remove before opening up in the upstream
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Use Private Information Retrieval to detect spent notes and fetch witnesses before sync completes, giving users early visibility into pending spends. Adds the full data flow (SDK synchronizer interface, Root reducer orchestration, shared state), a PIR setup screen in Advanced Settings with a persisted user toggle, and pending-spend UI treatment in transaction rows.
Motivation
During normal wallet sync, Orchard notes are not spendable until the
shard-tree scanner has processed enough blocks to construct a Merkle
authentication path for each note. For wallets that are catching up after
being offline, this can mean a significant delay before funds become
available.
Nullifier PIR (Private Information Retrieval) sidesteps this by querying
an external server for two pieces of information:
wallet mark notes as spent before the scanner confirms it.
needed to spend a note, so the wallet does not need to wait for its
local shard to be fully scanned.
Together, these allow the wallet to display accurate spendable balances
and build transactions within seconds of startup, rather than waiting for
a full scan.
Design Assumptions
Video Demo
https://screen.studio/share/tm6q8yUz
Related PRs
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