research: Poseidon2 Merkle-node hash (constraints + proving-time delta) - #46
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Measures swapping transfer.circom/compliance.circom's depth-20 Merkle-node hash from circomlib Poseidon to a Poseidon2 compression (@taceo/circom-lib, audited t=2 parameters): -660 R1CS constraints per circuit (-4.85%/-5.18%), -7.1% mean Node proving time on transfer.circom, cross-checked against an independent JS reference and confirmed to reject 4 classes of malicious witness. Kept as circuits/experiments/ only (not wired into contracts/, scripts/src/, or frontend/) — a production swap needs an off-chain tree-builder migration, a new timelocked VK, and a commitment-migration path. Verdict: PARK. On-chain gas (queue item 1) blocked a third night running: the proxy confirms a network-policy 403 to both fullnode.testnet.sui.io and github.com, not a missing binary. Full report: docs/research/2026-08-28-poseidon2-merkle-hash.md
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Summary
One iteration of the nightly cryptography/scalability research loop
(
docs/research/NIGHTLY_PROMPT.md). Full report:docs/research/2026-08-28-poseidon2-merkle-hash.md.transfer.circom/compliance.circom's depth-20Merkle-node hash from circomlib Poseidon to a Poseidon2 compression
(
@taceo/circom-lib, audited t=2 parameters) reduces constraint count andNode proving time.
transfer.circom,−5.18%
compliance.circom, −6.35% in an isolated Merkle-20 comparison),−4.31% zkey size, ~−7.1% mean Node proving time (n=20,
transfer.circom).Cross-checked the compiled circuit's Poseidon2 output bit-exact against the
independent
@taceo/poseidon2JS reference, and confirmed 4 classes ofmalicious witness (tampered sibling, tampered leaf, non-boolean path-index
bit, forged root) are rejected at witness-generation time.
circuits/experiments/(plus one new template,
templates/merkle_proof_poseidon2.circom) — theswap changes what the Merkle root means, so a real migration needs
synchronized updates to the off-chain tree builders
(
frontend/src/lib/merkle-tree.ts,scripts/src/compliance-utils.ts), a newtimelocked VK + ceremony contribution, and a path for already-deposited
commitments. Verdict: PARK.
confirmed as an outbound network-policy 403 to both
fullnode.testnet.sui.ioandgithub.com(not a missing binary), so theloop moved to queue item 2 instead. See "Open questions" in the report and
the re-ranked
docs/research/EXPERIMENTS.md.Test plan
circuits:test/transfer.test.mjs43/43,test/compliance.test.mjs30/30,
test/withdraw.test.mjs35/35 — all green, no production circuittouched.
circuits/experiments/poseidon2-merkle.test.mjs— 6/6 (2 correctness, 4negative/malicious-witness tests).
frontend:bun run lintclean,bun run test19/19.scripts:bun run test109/109.contracts(Move): not run — nosuiCLI available this session (seeabove), no contract code changed.
Generated by Claude Code