MD5加密算法原理及实现 C代码
时间: 2023-04-06 15:05:16 浏览: 176
MD5加密算法是一种常用的哈希函数,它可以将任意长度的消息压缩成一个128位的消息摘要。MD5算法的实现原理是将消息分成512位的块,每个块再分成16个32位的子块,然后通过一系列的位运算和非线性函数,对每个子块进行处理,最终得到一个128位的消息摘要。
以下是一个使用C语言实现MD5算法的代码示例:
```c
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#define ROTLEFT(a, b) ((a << b) | (a >> (32 - b)))
#define F(x, y, z) ((x & y) | (~x & z))
#define G(x, y, z) ((x & z) | (y & ~z))
#define H(x, y, z) (x ^ y ^ z)
#define I(x, y, z) (y ^ (x | ~z))
static const uint32_t K[] = {
0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee,
0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501,
0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be,
0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821,
0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa,
0xd62f105d, 0x2441453, 0xd8a1e681, 0xe7d3fbc8,
0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed,
0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a,
0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c,
0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70,
0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x4881d05,
0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665,
0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039,
0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1,
0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1,
0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391
};
static const uint32_t INIT[] = {
0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476
};
void md5_transform(uint32_t state[4], const uint8_t block[64]) {
uint32_t a = state[0], b = state[1], c = state[2], d = state[3], x[16];
memcpy(x, block, 64);
for (int i = 0; i < 64; i++) {
uint32_t f, g;
if (i < 16) {
f = F(b, c, d);
g = i;
} else if (i < 32) {
f = G(b, c, d);
g = (5 * i + 1) % 16;
} else if (i < 48) {
f = H(b, c, d);
g = (3 * i + 5) % 16;
} else {
f = I(b, c, d);
g = (7 * i) % 16;
}
uint32_t temp = d;
d = c;
c = b;
b = b + ROTLEFT((a + f + K[i] + x[g]), 7);
a = temp;
}
state[0] += a;
state[1] += b;
state[2] += c;
state[3] += d;
}
void md5(const uint8_t *initial_msg, size_t initial_len, uint8_t *digest) {
uint32_t state[4];
uint32_t bitlen[2] = {0, 0};
state[0] = INIT[0];
state[1] = INIT[1];
state[2] = INIT[2];
state[3] = INIT[3];
size_t new_len = ((((initial_len + 8) / 64) + 1) * 64) - 8;
uint8_t *msg = calloc(new_len + 64, 1);
memcpy(msg, initial_msg, initial_len);
msg[initial_len] = 128;
uint32_t bits_len = 8 * initial_len;
memcpy(msg + new_len, &bits_len, 4);
for (int i = 0; i < new_len; i += 64) {
md5_transform(state, msg + i);
}
memcpy(digest, state, 16);
free(msg);
}
int main() {
char *msg = "hello, world!";
uint8_t digest[16];
md5((uint8_t *) msg, strlen(msg), digest);
for (int i = 0; i < 16; i++) {
printf("%02x", digest[i]);
}
printf("\n");
return 0;
}
```