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

[retraca]

RISC0-based private M-of-N multisig primitive for LEZ.

Implementation: https://github.com/retraca/lp-0002-private-multisig

Members register voting commitments (SHA256("member" || nsk || multisig_id)). Voting generates a RISC0 receipt proving nsk knowledge without revealing which member voted. The on-chain program counts valid receipts and gates execution at threshold M.

Key design decisions:

• member_set_root = SHA256(c0 || ... || cN) in the journal — proves set membership without identifying the voter
• nullifier = SHA256("multisig/v1/vote" || nsk || proposal_id || multisig_id) — prevents double-voting per proposal
• LEZ nonce constraint avoided: voting commitments are separate from shielded spending accounts
• Four on-chain instructions: initialize, submit_proposal, vote, execute; error codes 6001–6011

See solutions/LP-0002.md for the full write-up, success criteria checklist, FURPS self-assessment, and terms acknowledgment.

[github-actions]

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ℹ️ Solution submission for LP-0002.
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