请使用C++不用OpenSSL库实现SM2椭圆曲线公钥加密算法

好的，下面是一个简单的示例代码实现SM2椭圆曲线公钥加密算法：

#include <iostream>
#include <string>
#include <cstring>
#include <cmath>
#include <vector>

using namespace std;

// SM2椭圆曲线参数
const int N = 256;  // 字节数
const int n = 32;  // 字节数组长度
const int w = 8;  // 字节位数
const int p = 0xfffffffeffffffffffffffffffffffffffffffff00000000ffffffffffffffff;  // 素数
const int a = 0xfffffffeffffffffffffffffffffffffffffffff00000000fffffffffffffffc;  // 系数a
const int b = 0x28e9fa9e9d9f5e344d5a9e4bcf6509a7f39789f515ab8f92d;  // 系数b
const int gx = 0x32c4ae2c1f1981195f9904466a39c9948fe30bbff2660be171;  // 基点Gx
const int gy = 0xbc3736a2f4f6779c59bdcee36b692153d0a9877cc62a474002df32e52139f0a0;  // 基点Gy
const int n0 = 1 << w;  // 字节的最高位

// 将整数转换为字节数组
vector<unsigned char> int2byte(int x) {
    vector<unsigned char> res(n);
    for (int i = 0; i < n; i++) {
        res[i] = x % n0;
        x >>= w;
    }
    return res;
}

// 将字节数组转换为整数
int byte2int(vector<unsigned char> bytes) {
    int res = 0;
    for (int i = n - 1; i >= 0; i--) {
        res <<= w;
        res += bytes[i];
    }
    return res;
}

// 模运算
int mod(int a, int b) {
    return (a % b + b) % b;
}

// 逆元运算
int inv(int a, int b) {
    int b0 = b, t, q;
    int x0 = 0, x1 = 1;
    if (b == 1) return 1;
    while (a > 1) {
        q = a / b;
        t = b, b = a % b, a = t;
        t = x0, x0 = x1 - q * x0, x1 = t;
    }
    if (x1 < 0) x1 += b0;
    return x1;
}

// 点加运算
vector<int> add(vector<int> P, vector<int> Q) {
    vector<int> R(3);
    int lambda;
    if (P[0] == Q[0] && P[1] == Q[1]) {
        lambda = mod(3 * P[0] * P[0] + a, p) * inv(2 * P[1], p) % p;
    } else {
        lambda = (Q[1] - P[1]) * inv(Q[0] - P[0], p) % p;
    }
    R[0] = mod(lambda * lambda - P[0] - Q[0], p);
    R[1] = mod(lambda * (P[0] - R[0]) - P[1], p);
    R[2] = 1;
    return R;
}

// 点倍运算
vector<int> mul(int k, vector<int> P) {
    vector<int> R = P;
    k--;
    while (k > 0) {
        if (k % 2 == 1) {
            R = add(R, P);
        }
        P = add(P, P);
        k /= 2;
    }
    return R;
}

// 生成公钥
vector<vector<int>> genPublicKey(int d) {
    vector<vector<int>> publicKey;
    vector<int> P(3);
    P[0] = gx;
    P[1] = gy;
    P[2] = 1;
    publicKey.push_back(mul(d, P));
    return publicKey;
}

// SM2加密
vector<unsigned char> sm2Encrypt(string plaintext, vector<vector<int>> publicKey) {
    // 将明文转换为字节数组
    vector<unsigned char> M(n);
    memcpy(&M[0], plaintext.c_str(), plaintext.length());
    // 生成随机数k
    int k = rand() % (p - 1) + 1;
    // 计算C1 = [k]G
    vector<int> G(3);
    G[0] = gx;
    G[1] = gy;
    G[2] = 1;
    vector<int> C1 = mul(k, G);
    // 计算S = [h]PB和C2 = M^T ^ kP
    vector<int> P = publicKey[0];
    vector<int> S = mul(h, P);
    vector<unsigned char> C2(n);
    for (int i = 0; i < n; i++) {
        C2[i] = M[i] ^ ((k * P[0] + S[0]) >> (w * i) & (n0 - 1));
    }
    // 拼接密文
    vector<unsigned char> ciphertext;
    ciphertext.insert(ciphertext.end(), int2byte(C1[0]).begin(), int2byte(C1[0]).end());
    ciphertext.insert(ciphertext.end(), int2byte(C1[1]).begin(), int2byte(C1[1]).end());
    ciphertext.insert(ciphertext.end(), C2.begin(), C2.end());
    return ciphertext;
}

int main() {
    // 生成公钥
    int d = 1234567890;  // 私钥
    vector<vector<int>> publicKey = genPublicKey(d);
    // 加密
    string plaintext = "Hello, world!";
    vector<unsigned char> ciphertext = sm2Encrypt(plaintext, publicKey);
    // 输出密文
    cout << "Ciphertext: ";
    for (unsigned char c : ciphertext) {
        printf("%02x", c);
    }
    cout << endl;
    return 0;
}

需要注意的是，以上代码仅为演示用途，实际使用时需要进行更加严格的错误处理和安全措施。