使用c++实现SHA-1算法

SHA-1是一种加密哈希算法，它将任意长度的消息压缩为一个160位的消息摘要。下面是使用C++实现SHA-1算法的示例代码：

#include <iostream>
#include <cstring>
#include <cstdint>

// 循环左移函数
#define ROTLEFT(a,b) ((a << b) | (a >> (32-b)))

// 定义常量K
const uint32_t K[] = {
    0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6
};

// SHA-1算法函数
void sha1(uint8_t* message, uint32_t message_length, uint32_t* digest) {
    // 初始化缓冲区
    uint32_t H[] = {
        0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0
    };
    // 计算填充位数
    uint32_t padding_length = 64 - ((message_length + 8) % 64);
    // 填充消息
    uint8_t* padded_message = new uint8_t[message_length + padding_length + 8];
    std::memcpy(padded_message, message, message_length);
    padded_message[message_length] = 0x80;
    std::memset(padded_message + message_length + 1, 0, padding_length - 1);
    // 将消息长度添加到消息末尾
    uint64_t message_bit_length = message_length * 8;
    std::memcpy(padded_message + message_length + padding_length, &message_bit_length, sizeof(message_bit_length));
    // 处理每个512位的分组
    for (uint32_t i = 0; i < message_length + padding_length + 8; i += 64) {
        // 将分组划分为16个32位的字
        uint32_t* w = new uint32_t[80];
        for (uint32_t j = 0; j < 16; j++) {
            w[j] = (padded_message[i + j * 4] << 24) |
                   (padded_message[i + j * 4 + 1] << 16) |
                   (padded_message[i + j * 4 + 2] << 8) |
                   (padded_message[i + j * 4 + 3]);
        }
        // 扩展16个字为80个字
        for (uint32_t j = 16; j < 80; j++) {
            w[j] = ROTLEFT(w[j-3] ^ w[j-8] ^ w[j-14] ^ w[j-16], 1);
        }
        // 初始化哈希值
        uint32_t a = H[0];
        uint32_t b = H[1];
        uint32_t c = H[2];
        uint32_t d = H[3];
        uint32_t e = H[4];
        // 主循环
        for (uint32_t j = 0; j < 80; j++) {
            uint32_t f, k;
            if (j < 20) {
                f = (b & c) | ((~b) & d);
                k = K[0];
            } else if (j < 40) {
                f = b ^ c ^ d;
                k = K[1];
            } else if (j < 60) {
                f = (b & c) | (b & d) | (c & d);
                k = K[2];
            } else {
                f = b ^ c ^ d;
                k = K[3];
            }
            uint32_t temp = ROTLEFT(a, 5) + f + e + k + w[j];
            e = d;
            d = c;
            c = ROTLEFT(b, 30);
            b = a;
            a = temp;
        }
        // 更新哈希值
        H[0] += a;
        H[1] += b;
        H[2] += c;
        H[3] += d;
        H[4] += e;
        // 释放内存
        delete[] w;
    }
    // 保存哈希值
    std::memcpy(digest, H, sizeof(H));
    // 释放内存
    delete[] padded_message;
}

int main() {
    uint8_t message[] = "hello world";
    uint32_t digest[5];
    sha1(message, std::strlen((const char*)message), digest);
    std::cout << std::hex << digest[0] << digest[1] << digest[2] << digest[3] << digest[4] << std::endl;
    return 0;
}

注意，这只是一个简单的示例代码，实际应用中需要考虑更多安全性和性能方面的问题。