Data Availability Research

Abstract

This research LP explores data availability (DA) solutions for the Lux Network, analyzing how to ensure data remains accessible for validation while optimizing storage costs. It examines different DA approaches, their trade-offs, and how Lux's multi-chain architecture can leverage specialized chains for efficient data availability.

Motivation

Data availability is crucial for:

1. Scalability: Enable high throughput without storing everything on-chain
2. Security: Ensure data can be validated when needed
3. Cost Efficiency: Reduce storage costs for users and validators
4. Decentralization: Prevent data withholding attacks
5. Interoperability: Support rollups and light clients

Current State

Data Storage in Lux

• C-Chain: Full EVM state storage
• X-Chain: UTXO model with pruning
• P-Chain: Validator and chain data
• Storage Costs: Growing with adoption

Current Data Patterns

// Data usage across Lux ecosystem
interface DataUsageProfile {
  chain_data: {
    c_chain: {
      state_size: "50GB+";
      growth_rate: "1GB/month";
      pruning: "Limited";
    };
    x_chain: {
      utxo_set: "10GB";
      growth_rate: "200MB/month";
      pruning: "Spent outputs";
    };
  };
  
  external_data: {
    ipfs: "NFT metadata, images";
    arweave: "Permanent storage needs";
    centralized: "High-frequency data";
  };
}

Research Findings

1. Data Availability Sampling (DAS)

Implementation for Lux

// Data availability sampling with erasure coding
contract DataAvailabilitySampling {
    struct DataCommitment {
        bytes32 root;           // Merkle root of data
        uint256 size;           // Original data size
        uint256 chunks;         // Number of erasure coded chunks
        uint256 minChunks;      // Minimum chunks to reconstruct
        uint256 timestamp;
        address submitter;
    }
    
    mapping(bytes32 => DataCommitment) public commitments;
    mapping(address => uint256) public samplerRewards;
    
    uint256 public constant SAMPLING_RATE = 20; // Sample 20% of chunks
    uint256 public constant ERASURE_RATE = 2;   // 2x redundancy
    
    // Submit data commitment
    function submitData(
        bytes32 dataRoot,
        uint256 dataSize,
        bytes32[] calldata chunkRoots
    ) external returns (bytes32 commitmentId) {
        uint256 numChunks = chunkRoots.length;
        uint256 minChunks = numChunks / ERASURE_RATE;
        
        commitmentId = keccak256(
            abi.encodePacked(dataRoot, block.timestamp)
        );
        
        commitments[commitmentId] = DataCommitment({
            root: dataRoot,
            size: dataSize,
            chunks: numChunks,
            minChunks: minChunks,
            timestamp: block.timestamp,
            submitter: msg.sender
        });
        
        emit DataCommitted(commitmentId, dataRoot, numChunks);
    }
    
    // Light clients sample random chunks
    function sampleAvailability(
        bytes32 commitmentId,
        uint256[] calldata chunkIndices,
        bytes[] calldata chunkProofs
    ) external {
        DataCommitment memory commitment = commitments[commitmentId];
        uint256 requiredSamples = (commitment.chunks * SAMPLING_RATE) / 100;
        
        require(
            chunkIndices.length >= requiredSamples,
            "Insufficient samples"
        );
        
        // Verify each chunk proof
        for (uint256 i = 0; i < chunkIndices.length; i++) {
            require(
                verifyChunkProof(
                    commitment.root,
                    chunkIndices[i],
                    chunkProofs[i]
                ),
                "Invalid chunk proof"
            );
        }
        
        // Reward sampler
        samplerRewards[msg.sender] += SAMPLING_REWARD;
        
        emit AvailabilitySampled(commitmentId, msg.sender, chunkIndices.length);
    }
}

2. Specialized DA Chain Design

Z-Chain as Data Availability Layer

// Z-Chain optimized for data availability
contract ZChainDataAvailability {
    struct DataBlob {
        bytes32 id;
        uint256 size;
        uint256 expiryBlock;
        bytes32 kzgCommitment;  // KZG polynomial commitment
        address publisher;
        uint256 fee;
    }
    
    mapping(bytes32 => DataBlob) public blobs;
    mapping(address => bytes32[]) public publisherBlobs;
    
    // Publish data with KZG commitment
    function publishBlob(
        bytes calldata data,
        uint256 retentionBlocks
    ) external payable returns (bytes32 blobId) {
        // Calculate KZG commitment
        bytes32 commitment = computeKZGCommitment(data);
        
        // Calculate storage fee
        uint256 fee = calculateStorageFee(data.length, retentionBlocks);
        require(msg.value >= fee, "Insufficient fee");
        
        blobId = keccak256(
            abi.encodePacked(commitment, block.timestamp)
        );
        
        blobs[blobId] = DataBlob({
            id: blobId,
            size: data.length,
            expiryBlock: block.number + retentionBlocks,
            kzgCommitment: commitment,
            publisher: msg.sender,
            fee: msg.value
        });
        
        publisherBlobs[msg.sender].push(blobId);
        
        // Store in specialized DA storage
        _storeInDALayer(blobId, data);
        
        emit BlobPublished(blobId, commitment, data.length);
    }
    
    // Verify data availability without downloading
    function verifyAvailability(
        bytes32 blobId,
        uint256 index,
        bytes calldata proof
    ) external view returns (bool) {
        DataBlob memory blob = blobs[blobId];
        require(block.number < blob.expiryBlock, "Blob expired");
        
        return verifyKZGProof(
            blob.kzgCommitment,
            index,
            proof
        );
    }
}

3. Rollup Data Availability

Optimistic and ZK Rollup Support

// DA for Layer 2 solutions on Lux
contract RollupDataAvailability {
    struct RollupBatch {
        uint256 rollupId;
        uint256 batchNumber;
        bytes32 stateRoot;
        bytes32 dataRoot;
        uint256 timestamp;
        address sequencer;
    }
    
    mapping(uint256 => mapping(uint256 => RollupBatch)) public batches;
    mapping(uint256 => address) public rollupContracts;
    
    // Sequencers post batch data
    function postBatch(
        uint256 rollupId,
        uint256 batchNumber,
        bytes32 stateRoot,
        bytes calldata transactions
    ) external {
        require(
            msg.sender == getRollupSequencer(rollupId),
            "Not sequencer"
        );
        
        // Compute data commitment
        bytes32 dataRoot = merkleize(transactions);
        
        batches[rollupId][batchNumber] = RollupBatch({
            rollupId: rollupId,
            batchNumber: batchNumber,
            stateRoot: stateRoot,
            dataRoot: dataRoot,
            timestamp: block.timestamp,
            sequencer: msg.sender
        });
        
        // Store transaction data off-chain with availability proof
        _storeWithAvailabilityProof(rollupId, batchNumber, transactions);
        
        emit BatchPosted(rollupId, batchNumber, stateRoot, dataRoot);
    }
    
    // Fraud proof requires data availability
    function challengeStateTransition(
        uint256 rollupId,
        uint256 batchNumber,
        bytes calldata fraudProof,
        bytes calldata batchData
    ) external {
        RollupBatch memory batch = batches[rollupId][batchNumber];
        
        // Verify data matches commitment
        require(
            merkleize(batchData) == batch.dataRoot,
            "Invalid data"
        );
        
        // Verify fraud proof
        bool isValid = IFraudProver(rollupContracts[rollupId])
            .verifyFraudProof(
                batch.stateRoot,
                batchData,
                fraudProof
            );
        
        if (isValid) {
            // Slash sequencer and revert state
            _handleFraudProven(rollupId, batchNumber);
        }
    }
}

4. Hybrid Storage Solutions

On-chain/Off-chain Hybrid

// Intelligent data placement
contract HybridStorage {
    enum StorageTier {
        HOT,        // On-chain, frequently accessed
        WARM,       // IPFS with on-chain hash
        COLD,       // Arweave for permanent storage
        ARCHIVE     // Compressed off-chain storage
    }
    
    struct DataRecord {
        bytes32 id;
        bytes32 contentHash;
        StorageTier tier;
        string location;    // URI for off-chain storage
        uint256 accessCount;
        uint256 lastAccess;
    }
    
    mapping(bytes32 => DataRecord) public records;
    
    // Intelligently store based on predicted access patterns
    function storeData(
        bytes calldata data,
        uint256 expectedAccessFrequency
    ) external returns (bytes32 id) {
        bytes32 contentHash = keccak256(data);
        StorageTier tier = _determineTier(
            data.length,
            expectedAccessFrequency
        );
        
        id = keccak256(
            abi.encodePacked(contentHash, msg.sender, block.timestamp)
        );
        
        if (tier == StorageTier.HOT) {
            // Store on-chain
            _storeOnChain(id, data);
        } else {
            // Store off-chain and keep hash
            string memory location = _storeOffChain(data, tier);
            records[id] = DataRecord({
                id: id,
                contentHash: contentHash,
                tier: tier,
                location: location,
                accessCount: 0,
                lastAccess: block.timestamp
            });
        }
        
        emit DataStored(id, tier);
    }
    
    // Auto-migrate data between tiers based on usage
    function accessData(bytes32 id) external returns (bytes memory) {
        DataRecord storage record = records[id];
        record.accessCount++;
        record.lastAccess = block.timestamp;
        
        // Check if tier migration needed
        if (_shouldPromote(record)) {
            _migrateTier(id, StorageTier(uint(record.tier) - 1));
        }
        
        return _retrieveData(record);
    }
}

5. State Rent and Pruning

Economic Incentives for State Management

// State rent mechanism
contract StateRent {
    struct StateEntry {
        address owner;
        uint256 size;
        uint256 lastPayment;
        uint256 balance;
    }
    
    mapping(bytes32 => StateEntry) public stateEntries;
    uint256 public constant RENT_PER_BYTE_PER_BLOCK = 1 gwei;
    uint256 public constant GRACE_PERIOD = 90 days;
    
    // Pay rent for state storage
    function payRent(bytes32 stateId) external payable {
        StateEntry storage entry = stateEntries[stateId];
        entry.balance += msg.value;
        entry.lastPayment = block.timestamp;
        
        emit RentPaid(stateId, msg.value);
    }
    
    // Calculate rent due
    function rentDue(bytes32 stateId) public view returns (uint256) {
        StateEntry memory entry = stateEntries[stateId];
        uint256 blocksSincePayment = block.number - entry.lastPayment;
        
        return entry.size * RENT_PER_BYTE_PER_BLOCK * blocksSincePayment;
    }
    
    // Evict state if rent not paid
    function evictState(bytes32 stateId) external {
        StateEntry memory entry = stateEntries[stateId];
        
        require(
            block.timestamp > entry.lastPayment + GRACE_PERIOD,
            "Still in grace period"
        );
        
        uint256 rentOwed = rentDue(stateId);
        require(entry.balance < rentOwed, "Rent paid");
        
        // Archive state before deletion
        _archiveState(stateId);
        
        // Delete from active state
        delete stateEntries[stateId];
        
        emit StateEvicted(stateId, entry.owner);
    }
}

Recommendations

1. DA Architecture for Lux

recommended_architecture:
  primary_da_solution:
    chain: "Z-Chain specialized for DA"
    technology: "KZG commitments with DAS"
    features:
      - "Sub-second commitment generation"
      - "Logarithmic proof size"
      - "Fraud-proof compatible"
  
  storage_tiers:
    hot:
      location: "On-chain"
      use_case: "Active state, recent blocks"
      retention: "Permanent"
    
    warm:
      location: "IPFS cluster"
      use_case: "Recent transaction data"
      retention: "1 year"
    
    cold:
      location: "Arweave"
      use_case: "Historical data"
      retention: "Permanent"
  
  rollup_support:
    optimistic: "7-day challenge with DA proofs"
    zk: "Immediate finality with validity proofs"
    sovereign: "Independent DA with Lux security"

2. Implementation Strategy

1. Phase 1: Basic DA commitments on existing chains
2. Phase 2: Z-Chain specialization for DA
3. Phase 3: Full DAS implementation
4. Phase 4: Rollup ecosystem support

3. Economic Model

1. Storage Fees: Time-based pricing for data storage
2. Sampling Rewards: Incentivize light client participation
3. State Rent: Ongoing fees for active state
4. Archival Incentives: Rewards for historical data preservation

Implementation Roadmap

Phase 1: Basic DA (Q1 2025)

• Data commitment registry
• Basic availability proofs
• IPFS integration

Phase 2: Advanced DA (Q2 2025)

• KZG commitment scheme
• DAS implementation
• State rent mechanism

Phase 3: Ecosystem Integration (Q3 2025)

• Rollup DA support
• Cross-chain DA verification
• Economic incentives

Related Repositories

• DA Layer: https://github.com/luxfi/data-availability
• State Management: https://github.com/luxfi/state-rent
• IPFS Gateway: https://github.com/luxfi/ipfs-gateway
• Archival Node: https://github.com/luxfi/archive-node

Open Questions

1. Consensus Integration: How to integrate DA with consensus?
2. Light Client Security: Trust assumptions for sampling?
3. Cross-Chain DA: Shared DA layer for all chains?
4. Regulatory Compliance: Data retention requirements?

Conclusion

Data availability is a critical challenge for blockchain scalability. Lux's multi-chain architecture provides unique opportunities to create specialized DA solutions that balance security, efficiency, and decentralization. By leveraging Z-Chain for specialized DA functions and implementing modern techniques like DAS and KZG commitments, Lux can support a thriving ecosystem of rollups and high-throughput applications.

References

• Ethereum Data Availability
• Celestia DA Layer
• Polygon Avail
• EigenDA

Copyright

Copyright and related rights waived via CC0.

Specification

Algorithms, data structures, and parameters in this LP are normative and MUST be followed.

Rationale

Provides a pragmatic, secure path aligned with Lux’s ecosystem needs.

Backwards Compatibility

Additive; existing components remain compatible. Adoption can be staged.

Security Considerations

Adhere to best practices for validation, authentication, and cryptography to mitigate threats.