隐私保护开发指南

隐私保护开发指南

隐私保护是Web3应用中的重要组成部分。本章将介绍隐私保护的主要技术和实践方法。

零知识证明

1. zk-SNARK

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// 1. 验证器合约
contract SNARKVerifier {
    struct VerifyingKey {
        uint256[2] alpha;
        uint256[2] beta;
        uint256[2] gamma;
        uint256[2] delta;
        uint256[2][] ic;
    }

    VerifyingKey public vk;

    constructor(VerifyingKey memory _vk) {
        vk = _vk;
    }

    // 验证证明
    function verify(
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) public view returns (bool) {
        require(input.length + 1 == vk.ic.length, "Invalid input length");

        // 实现零知识证明验证逻辑
        return true;
    }
}

// 2. 隐私交易
contract PrivateTransaction {
    struct Note {
        uint256 commitment;
        uint256 nullifier;
        address owner;
    }

    mapping(uint256 => bool) public commitments;
    mapping(uint256 => bool) public nullifiers;

    SNARKVerifier public verifier;

    constructor(address _verifier) {
        verifier = SNARKVerifier(_verifier);
    }

    // 创建隐私交易
    function createTransaction(
        uint256 commitment,
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) public {
        require(!commitments[commitment], "Commitment already exists");
        require(
            verifier.verify(a, b, c, input),
            "Invalid proof"
        );

        commitments[commitment] = true;
    }

    // 花费隐私交易
    function spendTransaction(
        uint256 nullifier,
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) public {
        require(!nullifiers[nullifier], "Nullifier already spent");
        require(
            verifier.verify(a, b, c, input),
            "Invalid proof"
        );

        nullifiers[nullifier] = true;
    }
}

2. 环签名

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// 1. 环签名合约
contract RingSignature {
    struct PublicKey {
        uint256 x;
        uint256 y;
    }

    struct Signature {
        uint256[] c;
        uint256[] s;
    }

    // 验证环签名
    function verify(
        bytes32 message,
        PublicKey[] memory ring,
        Signature memory signature
    ) public pure returns (bool) {
        require(
            ring.length > 0 &&
            signature.c.length == ring.length &&
            signature.s.length == ring.length,
            "Invalid ring signature"
        );

        // 实现环签名验证逻辑
        return true;
    }

    // 生成密钥对
    function generateKeyPair(
        uint256 privateKey
    ) public pure returns (PublicKey memory) {
        // 实现密钥对生成逻辑
        return PublicKey({
            x: 0,
            y: 0
        });
    }
}

// 2. 匿名投票
contract AnonymousVoting {
    struct Vote {
        bytes32 proposal;
        PublicKey[] ring;
        Signature signature;
    }

    mapping(bytes32 => Vote[]) public votes;
    RingSignature public ringSignature;

    constructor(address _ringSignature) {
        ringSignature = RingSignature(_ringSignature);
    }

    // 投票
    function castVote(
        bytes32 proposal,
        PublicKey[] memory ring,
        Signature memory signature
    ) public {
        require(
            ringSignature.verify(proposal, ring, signature),
            "Invalid signature"
        );

        votes[proposal].push(Vote({
            proposal: proposal,
            ring: ring,
            signature: signature
        }));
    }

    // 获取投票数
    function getVoteCount(
        bytes32 proposal
    ) public view returns (uint256) {
        return votes[proposal].length;
    }
}

隐私交易

1. 混币器

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// 1. 混币器合约
contract Mixer {
    uint256 public constant DENOMINATION = 1 ether;
    uint256 public constant MERKLE_TREE_HEIGHT = 20;

    mapping(uint256 => bool) public commitments;
    mapping(uint256 => bool) public nullifiers;

    // 存款
    function deposit(uint256 commitment) public payable {
        require(msg.value == DENOMINATION, "Invalid amount");
        require(!commitments[commitment], "Commitment already exists");

        commitments[commitment] = true;
    }

    // 提款
    function withdraw(
        uint256 nullifier,
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) public {
        require(!nullifiers[nullifier], "Note already spent");

        // 验证零知识证明
        require(verifyProof(a, b, c, input), "Invalid proof");

        nullifiers[nullifier] = true;
        payable(msg.sender).transfer(DENOMINATION);
    }

    // 验证证明
    function verifyProof(
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) internal pure returns (bool) {
        // 实现证明验证逻辑
        return true;
    }
}

// 2. 隐私代币
contract PrivateToken {
    struct Note {
        uint256 amount;
        address owner;
        uint256 nonce;
        bool spent;
    }

    mapping(bytes32 => Note) public notes;

    // 创建票据
    function createNote(
        uint256 amount,
        bytes32 commitment
    ) public {
        require(!notes[commitment].spent, "Note already exists");

        notes[commitment] = Note({
            amount: amount,
            owner: msg.sender,
            nonce: block.number,
            spent: false
        });
    }

    // 转移票据
    function transferNote(
        bytes32 oldCommitment,
        bytes32 newCommitment,
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) public {
        require(!notes[oldCommitment].spent, "Note already spent");
        require(!notes[newCommitment].spent, "New note already exists");

        // 验证零知识证明
        require(verifyProof(a, b, c, input), "Invalid proof");

        notes[oldCommitment].spent = true;
        notes[newCommitment] = Note({
            amount: notes[oldCommitment].amount,
            owner: msg.sender,
            nonce: block.number,
            spent: false
        });
    }

    // 验证证明
    function verifyProof(
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) internal pure returns (bool) {
        // 实现证明验证逻辑
        return true;
    }
}

匿名系统

1. 匿名身份

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// 1. 身份注册
contract AnonymousIdentity {
    struct Identity {
        bytes32 commitment;
        uint256 treeIndex;
        bool registered;
    }

    mapping(bytes32 => Identity) public identities;
    uint256 public identityCount;

    // 注册身份
    function register(bytes32 commitment) public {
        require(!identities[commitment].registered, "Identity already registered");

        identities[commitment] = Identity({
            commitment: commitment,
            treeIndex: identityCount++,
            registered: true
        });
    }

    // 验证身份
    function verify(
        bytes32 commitment,
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) public view returns (bool) {
        require(identities[commitment].registered, "Identity not registered");

        // 验证零知识证明
        return verifyProof(a, b, c, input);
    }

    // 验证证明
    function verifyProof(
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) internal pure returns (bool) {
        // 实现证明验证逻辑
        return true;
    }
}

// 2. 匿名投票
contract AnonymousVotingSystem {
    struct Ballot {
        bytes32 proposal;
        mapping(bytes32 => bool) votes;
        uint256 voteCount;
    }

    mapping(bytes32 => Ballot) public ballots;
    AnonymousIdentity public identity;

    constructor(address _identity) {
        identity = AnonymousIdentity(_identity);
    }

    // 创建投票
    function createBallot(bytes32 proposal) public {
        require(ballots[proposal].proposal == bytes32(0), "Ballot already exists");

        ballots[proposal].proposal = proposal;
    }

    // 投票
    function vote(
        bytes32 proposal,
        bytes32 nullifier,
        uint256[2] memory a,
        uint256[2][2] memory b,
        uint256[2] memory c,
        uint256[] memory input
    ) public {
        Ballot storage ballot = ballots[proposal];
        require(ballot.proposal != bytes32(0), "Ballot does not exist");
        require(!ballot.votes[nullifier], "Already voted");

        // 验证身份
        require(
            identity.verify(nullifier, a, b, c, input),
            "Invalid identity proof"
        );

        ballot.votes[nullifier] = true;
        ballot.voteCount++;
    }

    // 获取投票结果
    function getVoteCount(
        bytes32 proposal
    ) public view returns (uint256) {
        return ballots[proposal].voteCount;
    }
}

数据加密

1. 同态加密

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// 1. 同态加密合约
contract HomomorphicEncryption {
    struct PublicKey {
        uint256 n;
        uint256 g;
    }

    struct Ciphertext {
        uint256 c;
        uint256 r;
    }

    // 加密
    function encrypt(
        uint256 message,
        PublicKey memory pk,
        uint256 random
    ) public pure returns (Ciphertext memory) {
        // 实现加密逻辑
        return Ciphertext({
            c: 0,
            r: 0
        });
    }

    // 同态加法
    function add(
        Ciphertext memory a,
        Ciphertext memory b,
        PublicKey memory pk
    ) public pure returns (Ciphertext memory) {
        // 实现同态加法逻辑
        return Ciphertext({
            c: 0,
            r: 0
        });
    }

    // 同态乘法
    function multiply(
        Ciphertext memory a,
        uint256 scalar,
        PublicKey memory pk
    ) public pure returns (Ciphertext memory) {
        // 实现同态乘法逻辑
        return Ciphertext({
            c: 0,
            r: 0
        });
    }
}

// 2. 隐私计算
contract PrivateComputation {
    struct Computation {
        bytes32 id;
        Ciphertext[] inputs;
        Ciphertext result;
        bool completed;
    }

    mapping(bytes32 => Computation) public computations;
    HomomorphicEncryption public encryption;

    constructor(address _encryption) {
        encryption = HomomorphicEncryption(_encryption);
    }

    // 提交计算
    function submitComputation(
        bytes32 id,
        Ciphertext[] memory inputs
    ) public {
        require(
            computations[id].id == bytes32(0),
            "Computation already exists"
        );

        computations[id] = Computation({
            id: id,
            inputs: inputs,
            result: Ciphertext({c: 0, r: 0}),
            completed: false
        });
    }

    // 执行计算
    function executeComputation(
        bytes32 id,
        PublicKey memory pk
    ) public {
        Computation storage computation = computations[id];
        require(!computation.completed, "Computation already completed");

        // 执行同态计算
        Ciphertext memory result = computation.inputs[0];
        for (uint i = 1; i < computation.inputs.length; i++) {
            result = encryption.add(result, computation.inputs[i], pk);
        }

        computation.result = result;
        computation.completed = true;
    }
}

练习题

  1. 实现一个简单的零知识证明验证器:
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// 练习:实现零知识证明验证器
contract ZKPVerifier {
    // 你的代码
}
  1. 创建环签名合约:
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// 练习:实现环签名
contract RingSignature {
    // 你的代码
}
  1. 实现混币器:
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// 练习:实现混币器
contract Mixer {
    // 你的代码
}
  1. 创建匿名身份系统:
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// 练习:实现匿名身份
contract AnonymousIdentity {
    // 你的代码
}
  1. 实现同态加密:
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// 练习:实现同态加密
contract HomomorphicEncryption {
    // 你的代码
}

参考资源

  1. ZoKrates文档
  2. Tornado Cash文档
  3. zkSync文档
  4. Aztec Protocol
  5. MACI文档