Developing Decentralized Insurance System
Nexus Mutual lost 8 million dollars in 2020—not from hack, but attacker manipulated claims voting process. Token holder deliberately voted against legitimate payouts to prevent dilution of own stake. Systemic problem of mechanism design, not contract vulnerability. Protocol we design must resist three attack classes simultaneously: economic (stake/voting manipulation), technical (reentrancy on claims, oracle manipulation) and governance (control capture via flash loan). None solved by "just write good contract".
Key Protocol Mechanics
Insurance Pool and Underwriting
Foundation—capital pool from LP provider funds accepting risk for premium share. Underwriting specific coverage (e.g., smart contract exploit on Aave v3)—create sub-pool with dedicated capital and risk-based pricing.
Pricing via Poisson model: claim probability λ multiplied by average payout μ. Premium = λ * μ * coverage_amount * duration. Parameters λ updated from historical claims—either manual governance or on-chain oracle with audit and incident data.
Problem: if risk parameters stored on-chain and governance-updated, attack vector appears—attacker can lobby lowering λ for specific protocol, buy cheap coverage, organize exploit, get payout. Protection: time lock on parameter updates + multisig with split keys for critical parameters.
Claims Verification—Most Complex Part
Three verification approaches, each with trade-offs:
Optimistic Verification (Kleros-style). Claim valid by default if uncontested over challenge_period (e.g., 72 hours). Contesting requires challenger stake. If contested—goes to arbitration via Kleros Court. Fast and cheap for uncontested, vulnerable to "silent majority"—no one contests because staking risk not worth it.
Commit-Reveal Voting of Assessors. Token holders stake, vote via hidden hashes, reveal. Majority gets reward, minority loses stake (Schelling point mechanics). Requires active community. Susceptible to flash loan attack: borrow tokens for voting, vote, return.
Flash loan voting protection: snapshot voting—voting rights determined by balance at block N, voting occurs block N+k. Flash loan doesn't work, tokens must be held before unknown event.
Parametric Trigger (Oracle). Payout happens automatically on on-chain event—price oracle deviated >X% over Y blocks, or TVL dropped >50% in 24 hours. No voting, covers only parametrically-describable risks. Suitable for depeg coverage, liquidation cascade, bridge exploit with public data.
We build hybrid system: parametric triggers for small auto-claims, commit-reveal with flash loan protection for large ones.
Capital Efficiency via Cover Tokens
LP deposits 100 ETH, gets cvETH—token representing pool share. cvETH usable in DeFi (staking, collateral) while no active claims. On claim activation for amount X, contract locks corresponding cvETH portion until verification completion. Prevents bank run: LP can't withdraw while pending claims against their portion.
Technical: ERC-4626 vault for capital pool + custom lockShares(address lp, uint256 amount) with ClaimsManager access control only.
Storage Layout and Contract Architecture
InsuranceCore (proxy UUPS)
├── CapitalPool (ERC-4626)
├── CoverageManager (create/manage coverage)
├── ClaimsManager (claims process)
│ ├── ParametricOracle (Chainlink + custom triggers)
│ └── VotingEngine (commit-reveal)
├── PricingEngine (premium calculation)
└── GovernanceTimelock (parameter changes)
Proxy UUPS with ERC-7201 namespaced storage—mandatory, protocol will upgrade. Without namespaced storage, first upgrade adding variable breaks ClaimsManager layout.
Typical Vulnerabilities We Close
Reentrancy on Payouts. ClaimsManager.processPayout() makes external token call. If coverage nominated in ERC-777 (with tokensReceived hook), attacker recursively calls processPayout before state update. Solution: nonReentrant + Checks-Effects-Interactions strictly, state change before transfer.
Oracle Manipulation via Flash Loan. Parametric trigger on price—attacker takes flash loan, dumps price on DEX, trigger fires, gets payout, repays. Protection: TWAP from Uniswap v3 instead spot, minimum 30-minute TWAP. Holding manipulated price 30 minutes on mainnet exceeds potential payout value at reasonable coverage.
Governance Takeover. Token-voting governance, borrowed tokens—capture possible. Standard: timelock on proposal execution (48-72 hours) giving community reaction window. Critical parameters: multisig >50% quorum + timelock. Guardian address for emergency veto.
Development Process
Analytics and Mechanism Design (1-2 weeks). Most important stage. Determine: what risks covered, capital pool structure, pricing mechanics, complete claims flow. Write formal spec with invariants—"capital pool always covers 100% active coverage", "claim never paid twice".
Contract Development (3-4 weeks). Solidity + Foundry. Each invariant—property-based test in Echidna. Fork-tests with real Chainlink oracles and Uniswap TWAP on mainnet data.
Internal Audit (1 week). Slither, Mythril, manual SWC checklist review. Focus: all payout paths, all parameter update points, all external calls.
External Audit (2-4 weeks). For >$500K TVL protocol—mandatory. Audit budget included upfront.
Testnet + Bug Bounty (1-2 weeks). Sepolia/Arbitrum Goerli deploy, open search program via Immunefi or Code4rena.
Mainnet Deploy. Via Gnosis Safe multisig. Initial TVL cap—"soft launch" with limited coverage proving mechanics.
Timeline Expectations
Basic protocol with parametric trigger and simple capital pool—4-6 weeks. Full system with assessor voting, governance, upgradability and audit—2-3 months. Strongly depends on mechanism design complexity upfront.
Cost calculated after detailed architecture discussion and covered-risk requirements.