隱私技術代碼範例進階指南

零知識電路範例

範圍證明電路

pragma circom 2.1.6;

template RangeProof(n) {
    signal input value;
    signal output bits[n];
    
    var lc = 0;
    for (var i = 0; i < n; i++) {
        bits[i] <-- value % 2;
        bits[i] * (1 - bits[i]) === 0;
        lc += bits[i] * (2 ** i);
    }
    lc === value;
}

Merkle 樹驗證

template MerkleTreeChecker(levels) {
    signal input leaf;
    signal input root;
    signal input pathElements[levels];
    signal input pathIndices[levels];
    
    signal hash[levels + 1];
    hash[0] === leaf;
    
    for (var i = 0; i < levels; i++) {
        // 選擇左右順序
        var left = hash[i];
        var right = pathElements[i];
        
        if (pathIndices[i] == 1) {
            left = pathElements[i];
            right = hash[i];
        }
        
        hash[i + 1] === Poseidon(left, right);
    }
    
    hash[levels] === root;
}

Solidity 驗證合約

contract Verifier {
    // 驗證 zkSNARK 證明
    function verifyProof(
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[3] memory input
    ) public view returns (bool) {
        return IVerifier(verifierAddress).verifyProof(
            a, b, c, input
        );
    }
}

應用場景代碼

隱私轉帳

function privateTransfer(
    bytes32 commitment,
    bytes calldata proof,
    bytes32 nullifier
) external {
    // 驗證承諾存在
    require(verifyMerkleProof(commitment, nullifier, proof));
    
    // 驗證 nullifier 未使用
    require(!usedNullifiers[nullifier]);
    
    // 標記為已使用
    usedNullifiers[nullifier] = true;
    
    // 轉帳
    emit Transfer(nullifier, msg.sender);
}

結語

代碼範例只是起點，真正的理解來自實際項目經驗。

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