038_零知识证明访问控制：隐私保护与权限验证的完美结合

// 零知识证明访问控制合约
contract ZKAccessControl {
    // 定义事件
    event AccessGranted(address indexed user, bytes32 resourceId);
    event AccessDenied(address indexed user, bytes32 resourceId);
    event VerificationKeyUpdated(bytes32 indexed vkId, uint256 timestamp);
    
    // 验证密钥存储
    mapping(bytes32 => IVerificationKey) public verificationKeys;
    
    // 资源访问控制
    mapping(bytes32 => mapping(address => bool)) public hasAccess;
    
    // 验证密钥接口
    interface IVerificationKey {
        function verifyProof(uint256[2] calldata a, uint256[2][2] calldata b, uint256[2] calldata c, uint256[1] calldata input) external view returns (bool);
    }
    
    // 设置验证密钥
    function setVerificationKey(bytes32 vkId, address vkAddress) external onlyOwner {
        verificationKeys[vkId] = IVerificationKey(vkAddress);
        emit VerificationKeyUpdated(vkId, block.timestamp);
    }
    
    // 验证访问权限证明
    function verifyAccess(bytes32 vkId, uint256[2] calldata a, uint256[2][2] calldata b, uint256[2] calldata c, bytes32 resourceId) external returns (bool) {
        // 检查验证密钥是否存在
        IVerificationKey vk = verificationKeys[vkId];
        require(address(vk) != address(0), "Verification key not found");
        
        // 准备公共输入：用户地址和资源ID的哈希
        bytes32 inputHash = keccak256(abi.encodePacked(msg.sender, resourceId));
        uint256[1] memory input = [uint256(inputHash)];
        
        // 验证零知识证明
        bool isValid = vk.verifyProof(a, b, c, input);
        
        if (isValid) {
            // 授予访问权限
            hasAccess[resourceId][msg.sender] = true;
            emit AccessGranted(msg.sender, resourceId);
        } else {
            emit AccessDenied(msg.sender, resourceId);
        }
        
        return isValid;
    }
    
    // 权限检查修饰器
    modifier canAccess(bytes32 resourceId) {
        require(hasAccess[resourceId][msg.sender], "Access denied");
        _;
    }
    
    // 受保护的资源访问示例
    function accessProtectedResource(bytes32 resourceId) external canAccess(resourceId) {
        // 资源访问逻辑
    }
    
    // 撤销访问权限
    function revokeAccess(bytes32 resourceId, address user) external onlyOwner {
        hasAccess[resourceId][user] = false;
    }
    
    // 合约所有者管理
    address private _owner;
    
    constructor() {
        _owner = msg.sender;
    }
    
    modifier onlyOwner() {
        require(msg.sender == _owner, "Not authorized");
        _;
    }
}

// Circom语言的属性验证电路示例
pragma circom 2.0.0;

include "circomlib/poseidon.circom";

// 属性验证电路
// 证明用户知道某个属性值x，使得x满足特定条件，并且知道对应的私钥
// 公共输入：用户地址的哈希
// 私有输入：用户私钥和属性值x
template AttributeVerification() {
    // 电路参数
    signal input privateKey;  // 用户私钥（私密）
    signal input attributeX;  // 属性值（私密）
    signal output publicHash; // 公共输入哈希
    
    // 计算公钥（从私钥派生）
    component poseidonPk = Poseidon(1);
    poseidonPk.inputs[0] <== privateKey;
    
    // 验证属性条件（例如：x > 18）
    signal condition;
    condition <== (attributeX > 18) ? 1 : 0;
    require(condition == 1);
    
    // 计算公共输入哈希
    component poseidonHash = Poseidon(1);
    poseidonHash.inputs[0] <== poseidonPk.out;
    publicHash <== poseidonHash.out;
}

component main = AttributeVerification();

// 使用SnarkJS库生成和验证零知识证明
const snarkjs = require("snarkjs");

async function generateAccessProof(privateKey, attributeX, resourceId) {
    try {
        // 读取证明密钥和验证密钥
        const { proof, publicSignals } = await snarkjs.groth16.fullProve(
            {
                privateKey: privateKey,
                attributeX: attributeX
            },
            "./circuit.wasm",
            "./proving_key.json"
        );
        
        // 准备提交给合约的证明格式
        const a = [proof.pi_a[0], proof.pi_a[1]];
        const b = [
            [proof.pi_b[0][1], proof.pi_b[0][0]],
            [proof.pi_b[1][1], proof.pi_b[1][0]]
        ];
        const c = [proof.pi_c[0], proof.pi_c[1]];
        
        return {
            a,
            b,
            c,
            publicSignals
        };
    } catch (error) {
        console.error("Error generating proof:", error);
        throw error;
    }
}

async function verifyWithContract(accessControlContract, vkId, proof, resourceId) {
    try {
        // 调用合约验证函数
        const result = await accessControlContract.methods
            .verifyAccess(vkId, proof.a, proof.b, proof.c, resourceId)
            .send({ from: userAddress });
        
        return result.events.AccessGranted ? true : false;
    } catch (error) {
        console.error("Error verifying with contract:", error);
        return false;
    }
}

// 使用示例
async function requestAccess(privateKey, attributeX, resourceId) {
    // 生成证明
    const proof = await generateAccessProof(privateKey, attributeX, resourceId);
    
    // 提交到合约验证
    const hasAccess = await verifyWithContract(
        accessControlContract,
        "age_verification_vk",
        proof,
        resourceId
    );
    
    if (hasAccess) {
        console.log("Access granted!");
        // 访问受保护资源
        await accessControlContract.methods
            .accessProtectedResource(resourceId)
            .send({ from: userAddress });
    } else {
        console.log("Access denied.");
    }
}

// 隐私保护的投票系统
contract PrivateVotingSystem {
    ZKAccessControl public accessControl;
    mapping(bytes32 => uint256) public voteCounts;
    bytes32 public proposalId;
    
    constructor(address _accessControlAddress, bytes32 _proposalId) {
        accessControl = ZKAccessControl(_accessControlAddress);
        proposalId = _proposalId;
    }
    
    // 投票函数（受零知识证明访问控制保护）
    function castVote(bytes32 option) external {
        // 检查访问权限
        require(accessControl.hasAccess(proposalId, msg.sender), "Not authorized to vote");
        
        // 增加投票计数
        voteCounts[option]++;
        
        // 记录投票事件（不包含选民身份）
        emit VoteCast(proposalId, option);
    }
    
    // 事件
    event VoteCast(bytes32 indexed proposalId, bytes32 indexed option);
}