Solution: LP-0002 Private M-of-N Multisig

[edenbd1]

A threshold multisig for LEZ where an approval is unlinkable to the member who
gave it — including to the other members — and the chain records only that the
threshold was met.

• Repo: https://github.com/edenbd1/lp-0002-private-multisig
• Video: https://youtu.be/cPVsWWBVEeE
• Solution file: solutions/LP-0002.md

What is verified on chain

Each approve declares a ChainedCall to a LEZ-native membership program, so
the privacy circuit composes it with a real env::verify and the sequencer
checks the receipt against the node-pinned PRIVACY_PRESERVING_CIRCUIT_ID. The
member set and the threshold are folded into the PDA address, so neither can be
invented nor lowered — a forged configuration resolves to an address nobody ever
created.

Transactions — a 2-of-3 lifecycle on the current public testnet

Step	Transaction
deploy membership_lez	fb8eb10f7f394286c109cb6502a1c95294180523f30d06f707fc087a589bea98
deploy multisig_verifier	517efe12a0b592abe4d21a03246866b95c4379483e87af62fd9f26f7b8fe45ff
create_multisig	2930c1db4521b7c0b912278f4025e430704cfb9a7ebfcb5d22c374fd7ce85b70
create_proposal	68d5127e1e5570936f8d78e9a2da4d485562566cd8b7487a59322bf059406978
approve (member A, privacy tx)	41f5bb99346a0bef6aa0c69243473a554b84f0f0ad65e460bbb6890b11644942
approve (member B, privacy tx)	ae006465f5f945b8ba2666f28a5357d0a2aab4af05508c9c2811e0101d0ac649
execute	b43e46505f571e31d6051f7da43563db605b6a74b90c670da2d3582d53412ecd

Check any of them:

curl -s -X POST https://testnet.lez.logos.co -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"getTransaction","params":["<hash>"]}'

The two deployment hashes are SHA256(borsh(bytecode)) of the binaries committed
under artifacts/programs/, so they can be recomputed from the repository
without trusting this table.

The accounts, which are the stronger evidence

Account	Address
multisig	4wqJXoEhqqqYknt1s7gHcgBL6pkfwNJDfhbVVeAqwtnX
proposal	E11Awng7j59dVft83VVrwftXp41roJPKY5QRMb45Zcoe
approval marker A	DaG2Qan1ie5YhEpcti2LMCsvbkYi7WjWxnNKvxiqxi7B
approval marker B	FMj5yL8cpcrQzN7xhENHC2vysTrNwbtokPbTYjr98rPt
execution marker	CpiuicNDii6uCeMXtjd1W6hek6Vq35HJ7k3mz1Q82Fui

./scripts/verify-onchain.sh reads all five and confirms the verifier program
owns them. Each approval marker exists only because a membership proof was
verified on chain, and nothing in the pair names a member — read them and you
learn the threshold was met, and nothing about who met it.

On the explorer: none of the seven render at the moment. Its indexer is
behind the chain — its own front page listed block 4351 while getLastBlockId
returned 4496 — so anything submitted recently is affected, by anyone.
./scripts/check-explorer.py re-measures that in a headless browser, with an
impossible hash as the control, and prints what it finds rather than asserting.

Note on versions

The testnet was reset onto a newer chain in August, so everything here was
rebuilt against LEZ v0.2.4 and redeployed. That is also why the repository
vendors SPEL: no published SPEL release builds against a current LEZ, and
vendor/spel/PATCH.md documents every change, how to reproduce the directory,
and when it should be deleted.

Against the criteria

61 tests, CI green on Linux and macOS, including a workflow that runs the whole
lifecycle against a real standalone LEZ sequencer with RISC0_DEV_MODE=0. CU
costs are measured rather than estimated, per instruction and per machine. The
Basecamp module ships as a .lgx with darwin-arm64 and linux-amd64 variants and
was verified loading in Basecamp 0.2.2, not merely built.

Happy to address anything in review.

[github-actions]

✅ Validation passed

A reviewer will assess against the prize criteria.
ℹ️ Solution submission for LP-0002.
ℹ️ Checking repo: https://github.com/edenbd1/lp-0002-private-multisig

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Automated check. See solution template and TERMS.