# Fraxtal Merkle 证明预言机

Fraxtal Merkle 预言机（Fraxtal-MOs）是一类预言机，利用 `eth_getProof` RPC 方法在以太坊 L2（如 Fraxtal）上证明 L1 状态。

### 概览

Fraxtal-MOs 利用四个关键合约来验证和传输状态。

[**FraxchainL1Block**](https://fraxscan.com/address/0x4200000000000000000000000000000000000015#code)

预部署合约，用作 L2 上 L1 区块哈希的注册表。

[**StateRootOracle**](https://fraxscan.com/address/0xeD403d48e2bC946438B5686AA1AD65056Ccf9512)

合约用于验证给定的区块头与通过 FraxchainL1Block 合约中继的 L1 区块哈希。该合约负责存储状态根哈希以及 L1 时间戳。

[**MerkleProofPriceSource**](https://fraxscan.com/address/0xe25d8aaa6df41b94a415ee39ccee0df6673b9bdb#code)

合约执行状态根验证。根据通过 eth\_getProof RPC 方法离线构建的默克尔证明，该合约将验证并提取“证明”的存储槽值到 L2 区块链。这些“证明”的值随后被传递给预言机本身。

传递这些“证明”值的过程是无信任的，任何人都可以提交与给定以太坊 L1 地址的预先批准的槽对应的有效默克尔证明。

[**FraxtalERC4626TransportOracle**](https://fraxscan.com/address/0x1b680f4385f24420d264d78cab7c58365ed3f1ff#readContract)

合约接受来自 MerkleProofPriceSoure 合约的“证明” L1 数据。

对于 sFrax 和其他 ERC4626 保险库，这些“证明”的值定义了 L1 上保险库代币价值累积函数的当前斜率。

这些预言机公开以下函数，以允许用户查询相关资产的价格：

```solidity
    /// @dev Adheres to chainlink's AggregatorV3Interface `latestRoundData()`
    /// @return _roundId The l1Block corresponding to the last time the oracle was proofed
    /// @return _answer The price of Sfrax in frax
    /// @return _startedAt The L1 timestamp corresponding to most recent proof
    /// @return _updatedAt Equivalent to `_startedAt`
    /// @return _answeredInRound Equivalent to `_roundId`
    function latestRoundData()
        external
        view
    returns (
        uint80 _roundId, 
        int256 _answer, 
        uint256 _startedAt, 
        uint256 _updatedAt, 
        uint80 _answeredInRound
    )

```

```solidity
/// @return _pricePerShare The current exchange rate of the vault token 
///                        denominated in the underlying vault asset
function pricePerShare() public view 
```

#### 架构

将 L1 数据传输/证明到 L2 的过程：

步骤 1: 在 L2 上证明 L1 的区块头。

![Screenshot 2024-09-23 at 11.04.48 AM](https://hackmd.io/_uploads/HkR4EZyAR.png)

步骤 2: 提交预定义 L1 地址和存储槽的存储证明。

![Screenshot 2024-09-23 at 11.05.00 AM](https://hackmd.io/_uploads/H1ih4-J0C.png)

#### 演示客户端

以下代码应作为生成上述 Fraxtal 智能合约接受的函数参数的示例。\
有关 RPC 方法的文档：`eth_getBlockByNumber` 和 `eth_getProof`生成 L1 区块头的代码。

#### 生成 L1 区块头的代码

```typescript
async function getHeaderFromBlock(provider, blockL1) {
    let block = await provider.send("eth_getBlockByNumber", [blockL1, false])
    let headerFields = [];
    headerFields.push(block.parentHash);
    headerFields.push(block.sha3Uncles);
    headerFields.push(block.miner);
    headerFields.push(block.stateRoot);
    headerFields.push(block.transactionsRoot);
    headerFields.push(block.receiptsRoot);
    headerFields.push(block.logsBloom);
    headerFields.push(block.difficulty);
    headerFields.push(block.number);
    headerFields.push(block.gasLimit);
    headerFields.push(block.gasUsed);
    headerFields.push(block.timestamp);
    headerFields.push(block.extraData);
    headerFields.push(block.mixHash);
    headerFields.push(block.nonce);
    headerFields.push(block.baseFeePerGas);
    if (block.withdrawalsRoot) {
        headerFields.push(block.withdrawalsRoot);
    }
    if (block.blobGasUsed) {
        headerFields.push(block.blobGasUsed);
    }
    if (block.excessBlobGas) {
        headerFields.push(block.excessBlobGas);
    }
    if (block.parentBeaconBlockRoot) {
        headerFields.push(block.parentBeaconBlockRoot);
    }
    convertHeaderFields(headerFields);
    let header = ethers.utils.RLP.encode(headerFields);
    return header
}
```

#### 生成存储证明的代码

```typescript
        let blockToProof = "0x"+blockL1.toHexString().substring(2).replace(/^0+/, "");

        let sfrax_proof = await mainnetProvider.send("eth_getProof", 
        [
            // L1 address to generate proofs for
            SFRAX_MAINNET,
            // Slots to proof 
            [
                "0x0000000000000000000000000000000000000000000000000000000000000002",
                "0x0000000000000000000000000000000000000000000000000000000000000009",
                "0x0000000000000000000000000000000000000000000000000000000000000008",
                "0x0000000000000000000000000000000000000000000000000000000000000006",
                "0x0000000000000000000000000000000000000000000000000000000000000007"
            ], 
            blockToProof
        ]);
    
        // Format the proof info returned from `eth_getProof`
        let proof: Proof = {} as Proof;
        proof._accountProofSfrax = sfrax_proof.accountProof;
        proof._storageProofTotalSupply = sfrax_proof.storageProof[0].proof;
        proof._storageProofTotalAssets = sfrax_proof.storageProof[1].proof;
        proof._storageProofLastDist = sfrax_proof.storageProof[2].proof;
        proof._storageProofRewardsPacked = sfrax_proof.storageProof[3].proof;
        proof._storageProofRewardsCycleAmount = sfrax_proof.storageProof[4].proof;

        let txn = await proover.addRoundDataSfrax(
            SFRAX_L2_ORACLE,
            blockL1.toString(),
            proof
        )
```

#### 已部署的合约

| Description    | Oracle                                                                                                                       | MerkleProofPriceSource                                                                                                       |
| -------------- | ---------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- |
| sFrax/Frax     | [`0x1b680f4385f24420d264d78cab7c58365ed3f1ff`](https://fraxscan.com/address/0x1b680f4385f24420d264d78cab7c58365ed3f1ff#code) | [`0xe25d8aaa6df41b94a415ee39ccee0df6673b9bdb`](https://fraxscan.com/address/0xe25d8aaa6df41b94a415ee39ccee0df6673b9bdb#code) |
| sfrxEth/frxEth | [`0xEE095b7d9191603126Da584a1179BB403a027c3A`](https://fraxscan.com/address/0xEE095b7d9191603126Da584a1179BB403a027c3A#code) | [`0xabca0b314d15B3e28F24AC0ee84A63001d1b44Db`](https://fraxscan.com/address/0xabca0b314d15B3e28F24AC0ee84A63001d1b44Db#code) |
| FPI/USD        | [`0x0f50beeE2d2506634b1e6230F3867e30763CbB02`](https://fraxscan.com/address/0x0f50beeE2d2506634b1e6230F3867e30763CbB02#code) | [`0x8fc7425Cd36D7e4605650198099e4539238e9c37`](https://fraxscan.com/address/0x8fc7425Cd36D7e4605650198099e4539238e9c37#code) |


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