md5加解密代码c语言实现

MD5（Message Digest Algorithm 5）是一种常用的哈希算法，用于生成数据的摘要。下面是使用C语言实现MD5加解密的代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

typedef uint8_t BYTE;
typedef uint32_t WORD;

#define BUFFER_SIZE 64
#define CHUNK_SIZE 512

// 填充原始消息
void padding(BYTE *message, int length) {
    int remainder = length % BUFFER_SIZE;
    int padding_size = (remainder < (BUFFER_SIZE - 8)) ? (BUFFER_SIZE - 8 - remainder) : (2 * BUFFER_SIZE - 8 - remainder);
    BYTE padding[padding_size];
    padding[0] = 0x80;

    for (int i = 1; i < padding_size; i++) {
        padding[i] = 0;
    }

    WORD message_length_bits = length * 8;
    memcpy(message + length, padding, padding_size);
    memcpy(message + length + padding_size, &message_length_bits, sizeof(WORD));
}

// 左循环移位
WORD rotate_left(WORD x, int n) {
    return (x << n) | (x >> (32 - n));
}

// MD5压缩函数
void md5_compress(BYTE *chunk, WORD *state) {
    WORD a = state[0], b = state[1], c = state[2], d = state[3];
    WORD x[16];

    for (int i = 0; i < 16; i++) {
        x[i] = *(WORD *)(chunk + i * 4);
    }

    // Round 1
    WORD round1[] = {0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
                     0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
                     0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
                     0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821};
    for (int i = 0; i < 16; i++) {
        WORD f = (b & c) | ((~b) & d);
        WORD g = i;
        WORD temp = d;
        d = c;
        c = b;
        b = b + rotate_left((a + f + round1[i] + x[g]), 7);
        a = temp;
    }

    // Round 2
    WORD round2[] = {0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
                     0xd62f105d, 0x2441453, 0xd8a1e681, 0xe7d3fbc8,
                     0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
                     0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a};
    for (int i = 16; i < 32; i++) {
        WORD f = (d & b) | ((~d) & c);
        WORD g = (5 * i + 1) % 16;
        WORD temp = d;
        d = c;
        c = b;
        b = b + rotate_left((a + f + round2[i - 16] + x[g]), 12);
        a = temp;
    }

    // Round 3
    WORD round3[] = {0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
                     0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
                     0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x4881d05,
                     0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665};
    for (int i = 32; i < 48; i++) {
        WORD f = b ^ c ^ d;
        WORD g = (3 * i + 5) % 16;
        WORD temp = d;
        d = c;
        c = b;
        b = b + rotate_left((a + f + round3[i - 32] + x[g]), 17);
        a = temp;
    }

    // Round 4
    WORD round4[] = {0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
                     0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
                     0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
                     0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391};
    for (int i = 48; i < 64; i++) {
        WORD f = c ^ (b | (~d));
        WORD g = (7 * i) % 16;
        WORD temp = d;
        d = c;
        c = b;
        b = b + rotate_left((a + f + round4[i - 48] + x[g]), 22);
        a = temp;
    }

    // 更新状态
    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
}

// 计算MD5
void md5_hash(BYTE *message, int length, BYTE *hash) {
    WORD state[] = {0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476};
    int num_chunks = (length + BUFFER_SIZE) / CHUNK_SIZE;

    // 遍历消息的所有块进行压缩
    for (int i = 0; i < num_chunks; i++) {
        BYTE chunk[CHUNK_SIZE] = {0};

        if (i != num_chunks - 1) {
            // 非末尾块
            memcpy(chunk, message + i * CHUNK_SIZE, CHUNK_SIZE);
        } else {
            // 末尾块
            int chunk_size = length % CHUNK_SIZE;
            memcpy(chunk, message + i * CHUNK_SIZE, chunk_size);
            padding(chunk, chunk_size);
        }

        md5_compress(chunk, state);
    }

    // 生成摘要
    memcpy(hash, state, 16);
}

int main() {
    char input[] = "Hello, World!";
    BYTE hash[16];

    md5_hash((BYTE *)input, strlen(input), hash);

    printf("MD5 hash: ");
    for (int i = 0; i < 16; i++) {
        printf("%02x", hash[i]);
    }
    printf("\n");

    return 0;
}

以上是一个简单的用C语言实现的MD5加解密代码示例。它包括填充原始消息、左循环移位、MD5压缩函数、计算MD5等功能。示例代码通过将字符串"Hello, World!"计算出其对应的MD5摘要，并将其打印出来。您可以根据自己的需求修改该代码以适应其他情况。