c++实现md5加密

以下是使用C++实现MD5加密的代码示例：

#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <cmath>

using namespace std;

typedef unsigned int uint32;
typedef unsigned char uint8;

const uint32 T[64] = {
    0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
    0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
    0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
    0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
    0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
    0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8,
    0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
    0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
    0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
    0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
    0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05,
    0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
    0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
    0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
    0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
    0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
};

const uint32 A = 0x67452301;
const uint32 B = 0xefcdab89;
const uint32 C = 0x98badcfe;
const uint32 D = 0x10325476;

uint32 X[16];

uint32 rotate_left(uint32 x, uint32 n) {
    return (x << n) | (x >> (32 - n));
}

void md5_transform(uint32 *state, uint8 *block) {
    uint32 a = state[0], b = state[1], c = state[2], d = state[3];
    uint32 k, f, g;
    for (int i = 0; i < 64; i++) {
        if (i < 16) {
            k = i;
            f = (b & c) | ((~b) & d);
            g = i;
        } else if (i < 32) {
            k = (5 * i + 1) % 16;
            f = (d & b) | ((~d) & c);
            g = (5 * i + 1) % 16;
        } else if (i < 48) {
            k = (3 * i + 5) % 16;
            f = b ^ c ^ d;
            g = (3 * i + 5) % 16;
        } else {
            k = (7 * i) % 16;
            f = c ^ (b | (~d));
            g = (7 * i) % 16;
        }
        uint32 temp = d;
        d = c;
        c = b;
        b = b + rotate_left((a + f + T[i] + X[k]), g);
        a = temp;
    }
    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
}

void md5(const uint8 *initial_msg, size_t initial_len, uint8 *digest) {
    uint32 h0, h1, h2, h3;
    h0 = A;
    h1 = B;
    h2 = C;
    h3 = D;
    uint8 *msg = NULL;
    size_t new_len, offset;
    uint32 bits_len;
    new_len = (initial_len * 8 + 64 + 512) / 512 * 512 / 8;
    msg = (uint8 *)malloc(new_len);
    memcpy(msg, initial_msg, initial_len);
    msg[initial_len] = 0x80;
    offset = initial_len + 1;
    while (offset < new_len - 8) {
        msg[offset++] = 0;
    }
    bits_len = initial_len * 8;
    memcpy(msg + new_len - 8, &bits_len, 4);
    memset(msg + new_len - 4, 0, 4);
    for (offset = 0; offset < new_len; offset += (512 / 8)) {
        for (int i = 0; i < 16; i++) {
            X[i] = ((uint32)msg[offset + 4 * i]) |
                   (((uint32)msg[offset + 4 * i + 1]) << 8) |
                   (((uint32)msg[offset + 4 * i + 2]) << 16) |
                   (((uint32)msg[offset + 4 * i + 3]) << 24);
        }
        md5_transform(&h0, (uint8 *)X);
        md5_transform(&h1, (uint8 *)X);
        md5_transform(&h2, (uint8 *)X);
        md5_transform(&h3, (uint8 *)X);
    }
    free(msg);
    memcpy(digest, &h0, 4);
    memcpy(digest + 4, &h1, 4);
    memcpy(digest + 8, &h2, 4);
    memcpy(digest + 12, &h3, 4);
}

int main() {
    uint8 digest[16];
    char msg[] = "Hello, world!";
    md5((uint8 *)msg, strlen(msg), digest);
    for (int i = 0; i < 16; i++) {
        printf("%02x", digest[i]);
    }
    printf("\n");
    return 0;
}