# WIA-LEG-006: Digital Asset Inheritance Standard
## Version 1.2 - Phase 3: Smart Contract Protocol

**Status:** Final
**Published:** 2025-03-01
**Authors:** WIA Technical Committee on Digital Legacy
**License:** MIT License
**Requires:** v1.0 (Phase 1), v1.1 (Phase 2)

---

## 1. Introduction

### 1.1 Purpose
Phase 3 specifies on-chain smart contract protocols for automated, trustless digital asset inheritance execution.

### 1.2 Scope
- Multi-signature wallet schemes
- Dead man's switch implementations
- Oracle integration protocols
- Cross-chain coordination
- Smart contract security requirements

---

## 2. Multi-Signature Inheritance Contracts

### 2.1 Standard 2-of-3 Multi-Sig
```solidity
interface IInheritanceMultiSig {
    function transferInheritance(
        address beneficiary,
        uint256 amount
    ) external requiresTwoSignatures;

    function checkIn() external onlyOwner;

    function getInactivityPeriod() external view returns (uint256);
}
```

### 2.2 Configuration Parameters
- `totalSigners`: 2-10 (recommended: 3)
- `requiredSignatures`: 1 to totalSigners (recommended: 2)
- `timeLockPeriod`: 0-30 days (recommended: 14)

### 2.3 Security Requirements
- Formal verification of multi-sig logic
- Third-party audit by certified auditor
- Time-delay between approval and execution
- Emergency pause mechanism

---

## 3. Dead Man's Switch Protocol

### 3.1 Heartbeat Contract Interface
```solidity
interface IDeadManSwitch {
    function checkIn(bytes memory biometricProof) external;
    function updateState() external;
    function executeInheritance() external;

    function lastCheckIn() external view returns (uint256);
    function currentState() external view returns (State);

    enum State { Active, Warning, Grace, Triggered }
}
```

### 3.2 State Transitions
- **Active → Warning:** `timeSinceCheckIn > (checkInInterval - warningPeriod)`
- **Warning → Grace:** `timeSinceCheckIn > checkInInterval`
- **Grace → Triggered:** `timeSinceCheckIn > (checkInInterval + gracePeriod)`
- **Any → Active:** Owner successful check-in

### 3.3 Check-In Requirements
- Biometric verification (optional but recommended)
- Location verification (geofencing)
- Device fingerprinting
- Multi-factor authentication

### 3.4 Notification System
- On-chain events for each state transition
- Off-chain notification service integration
- Progressive urgency levels
- Multiple notification channels

---

## 4. Oracle Integration

### 4.1 Death Certificate Oracle Interface
```solidity
interface IDeathCertificateOracle {
    function reportDeath(
        bytes32 ssnHash,
        uint256 timestamp,
        bytes memory oracleSignature,
        bytes32[] memory proof
    ) external;

    function verifyDeath(bytes32 ssnHash)
        external view returns (bool verified, uint256 timestamp);
}
```

### 4.2 Oracle Requirements
- Minimum 3 independent oracle confirmations
- Oracle identity verification via WIA-IDENTITY
- Merkle proof for data authenticity
- Time window for confirmations (max 30 days)

### 4.3 Supported Oracle Types
- Government vital statistics offices
- Medical examiner systems
- Probate court systems
- Licensed death certificate verification services

### 4.4 Oracle Security
- Oracle reputation system
- Slashing for false reports
- Dispute resolution mechanism
- Appeal period (30-90 days)

---

## 5. Conditional Distribution Logic

### 5.1 Age-Based Distribution
```solidity
interface IAgeBasedInheritance {
    struct DistributionSchedule {
        uint256 ageRequired;
        uint256 percentage;
    }

    function claimInheritance(address beneficiary) external;
    function getClaimableAmount(address beneficiary)
        external view returns (uint256);
}
```

### 5.2 Milestone-Based Distribution
- Educational achievement verification
- Professional certification confirmation
- Custom condition evaluation
- Verifiable credential integration

---

## 6. Cross-Chain Coordination

### 6.1 Unified Trigger Protocol
```
1. Oracle Network broadcasts trigger event
2. Each blockchain's contract receives trigger
3. Contracts enter "pending" state
4. Coordination period (24 hours)
5. Synchronized execution across chains
```

### 6.2 Cross-Chain Message Format
```json
{
  "planId": "UUID",
  "triggerType": "oracle|manual|deadman",
  "triggerTimestamp": "Unix timestamp",
  "triggerHash": "SHA-256 hash",
  "sourceChain": "chainId",
  "signatures": []
}
```

### 6.3 Supported Bridge Protocols
- LayerZero for cross-chain messaging
- Chainlink CCIP for secure cross-chain transfers
- Axelar for cross-chain communication
- Wormhole for multi-chain coordination

---

## 7. Smart Contract Security Standards

### 7.1 Mandatory Security Measures
- Reentrancy guards on all external calls
- Integer overflow/underflow protection
- Access control on sensitive functions
- Circuit breakers for emergency situations
- Time-locks on critical operations

### 7.2 Formal Verification Requirements
- Theorem proving for core logic
- Model checking for state transitions
- Symbolic execution for all paths
- Property-based testing

### 7.3 Audit Requirements
- Minimum 2 independent audits
- Auditors from WIA-approved list
- Public audit reports required
- Bug bounty program (min $50k pool)

### 7.4 Testing Requirements
- 100% code coverage
- Fuzzing tests (min 100k iterations)
- Mainnet fork testing
- Gas optimization analysis

---

## 8. Gas Optimization

### 8.1 Storage Optimization
- Pack related variables into single slots
- Use events for historical data
- Minimize SSTORE operations
- Use calldata instead of memory where possible

### 8.2 Computation Optimization
- Off-chain computation with on-chain verification
- Batch operations where feasible
- Early returns to save gas
- View functions for read operations

### 8.3 Layer 2 Deployment
- Primary deployment on L2 (Arbitrum, Optimism, Polygon)
- L1 deployment for high-value estates
- Cross-layer communication support

---

## 9. Emergency Procedures

### 9.1 Contract Pause
```solidity
function emergencyPause() external onlyEmergencyMultiSig {
    require(!paused, "Already paused");
    paused = true;
    emit EmergencyPause(block.timestamp);
}
```

### 9.2 Emergency Withdrawal
- Requires M-of-N emergency multisig
- 7-day time-lock after pause
- All beneficiaries notified
- Funds sent to secure backup address

### 9.3 Contract Upgrade
- Proxy pattern for upgradeability
- Time-locked upgrades (min 14 days)
- Beneficiary approval for major upgrades
- Immutable core inheritance logic

---

## 10. Blockchain-Specific Implementations

### 10.1 Ethereum (EVM)
- Solidity 0.8.20+
- ERC-20/ERC-721 integration
- ENS domain support
- Gas optimization for Layer 1

### 10.2 Bitcoin
- Multi-sig P2WSH addresses
- Time-locked transactions (nLockTime)
- Taproot-based complex scripts
- Lightning Network inheritance

### 10.3 Solana
- Rust-based programs
- SPL token support
- Program Derived Addresses (PDAs)
- Low-latency execution

### 10.4 Cardano
- Plutus smart contracts
- Native token support
- eUTXO model considerations
- Formal verification friendly

---

## 11. Integration with Phase 2 APIs

### 11.1 Contract Deployment
- `POST /contracts/deploy` endpoint
- Returns contract address and transaction hash
- Automatic verification on block explorers

### 11.2 Contract Interaction
- `POST /contracts/{address}/call` for function calls
- Gas estimation before execution
- Transaction status tracking

### 11.3 Event Monitoring
- Webhook notifications for contract events
- Real-time event streaming
- Historical event queries

---

## 12. Reference Implementations

### 12.1 GitHub Repository
`https://github.com/WIA-Official/inheritance-contracts`

### 12.2 Deployed Contracts
- Ethereum Mainnet: `0x...`
- Polygon: `0x...`
- Arbitrum: `0x...`
- Optimism: `0x...`

### 12.3 Contract Verification
All contracts verified on Etherscan, PolygonScan, Arbiscan

---

## 13. References

- Ethereum Smart Contracts: https://ethereum.org/en/developers/docs/smart-contracts/
- Solidity Documentation: https://docs.soliditylang.org/
- OpenZeppelin Contracts: https://docs.openzeppelin.com/contracts/
- ConsenSys Smart Contract Best Practices: https://consensys.github.io/smart-contract-best-practices/

---

**弘益人間 · Benefit All Humanity**

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Licensed under MIT License