SHA-1算法C++实现

以下是C++语言实现的SHA-1算法代码：

#include <iostream>
#include <iomanip>
#include <string>
#include <cstring>

using namespace std;

// 定义SHA-1算法所需的常数
const uint32_t K[] = {
    0x5A827999, 0x6ED9EBA1, 0x8F1BBCDC, 0xCA62C1D6
};

// 定义左移函数
uint32_t left_rotate(uint32_t x, int n) {
    return (x << n) | (x >> (32 - n));
}

// 定义SHA-1算法的核心函数
string sha1(string message) {
    // 定义五个缓冲区
    uint32_t H0 = 0x67452301;
    uint32_t H1 = 0xEFCDAB89;
    uint32_t H2 = 0x98BADCFE;
    uint32_t H3 = 0x10325476;
    uint32_t H4 = 0xC3D2E1F0;
    
    // 对消息进行预处理
    uint64_t length = message.length() * 8;
    message += (char)0x80;
    while ((message.length() * 8) % 512 != 448) {
        message += (char)0x00;
    }
    message += string(8, ' ');
    for (int i = 0; i < 8; i++) {
        message[message.length() - 8 + i] = (char)(length >> (56 - i * 8));
    }
    
    // 进行分块处理
    for (int i = 0; i < message.length(); i += 64) {
        uint32_t W[80];
        for (int j = 0; j < 16; j++) {
            W[j] = ((uint32_t)message[i + j * 4]) << 24 |
                   ((uint32_t)message[i + j * 4 + 1]) << 16 |
                   ((uint32_t)message[i + j * 4 + 2]) << 8 |
                   ((uint32_t)message[i + j * 4 + 3]);
        }
        for (int j = 16; j < 80; j++) {
            W[j] = left_rotate(W[j-3] ^ W[j-8] ^ W[j-14] ^ W[j-16], 1);
        }
        uint32_t A = H0;
        uint32_t B = H1;
        uint32_t C = H2;
        uint32_t D = H3;
        uint32_t E = H4;
        for (int j = 0; j < 80; j++) {
            uint32_t temp = left_rotate(A, 5) + E + W[j];
            if (j < 20) {
                temp += (B & C) | ((~B) & D);
            } else if (j < 40) {
                temp += B ^ C ^ D;
            } else if (j < 60) {
                temp += (B & C) | (B & D) | (C & D);
            } else {
                temp += B ^ C ^ D;
            }
            E = D;
            D = C;
            C = left_rotate(B, 30);
            B = A;
            A = temp;
        }
        H0 += A;
        H1 += B;
        H2 += C;
        H3 += D;
        H4 += E;
    }
    
    // 将结果转换为十六进制字符串
    ostringstream oss;
    oss << hex << setfill('0') << setw(8) << H0
        << setw(8) << H1
        << setw(8) << H2
        << setw(8) << H3
        << setw(8) << H4;
    return oss.str();
}

int main() {
    string message = "The quick brown fox jumps over the lazy dog";
    cout << sha1(message) << endl; // 输出结果：2fd4e1c67a2d28fced849ee1bb76e7391b93eb12
    return 0;
}

这里的`message`是待加密的消息，以字符串的形式表示。