Md5加密实现 C语言

关注

原创最新推荐文章于 2026-03-20 01:15:22 发布 531 阅读 AI 写同款· GEO 优化 ›

一个简单的MD5加密算法C语言示例程序 #include #include #include #include typedef unsigned char *POINTER; typedef unsigned short int UINT2; typedef unsigned long int UINT4; typedef 阅读详情

35.1 前言

MD5加密算法全称为信息摘要算法，主要用途于校验，检验内容是否发生变化。其特点如下：

（1）长度固定。不管加密的内容多长，最后得到的结果长度都是一样的16个字节128bit；

（2）不可逆性。即使知道密文及加密方式但是却无法反向计算，因为摘要是部分内容，一个MD5

反向对应多个原始数据；

（3）常用于字符串及文本的加密；

35.2 MD5加密实现

Md5.h：

#ifndef MD5_H
#define MD5_H

typedef struct
{
	unsigned int count[2];
	unsigned int state[4];
	unsigned char buffer[64];
}MD5_CTX;

void MD5Init(MD5_CTX *context);
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen);
void MD5Final(MD5_CTX *context,unsigned char digest[16]);
int MD5EncryStr(unsigned char *output,unsigned char *input,unsigned int len);


#endif

Md5.c：

#include <string.h>
#include "md5.h"

#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))
#define ROTATE_LEFT(x,n) ((x << n) | (x >> (32-n)))
#define FF(a,b,c,d,x,s,ac) \
	{ \
		a += F(b,c,d) + x + ac; \
		a = ROTATE_LEFT(a,s); \
		a += b; \
	}
#define GG(a,b,c,d,x,s,ac) \
	{ \
		a += G(b,c,d) + x + ac; \
		a = ROTATE_LEFT(a,s); \
		a += b; \
	}
#define HH(a,b,c,d,x,s,ac) \
	{ \
		a += H(b,c,d) + x + ac; \
		a = ROTATE_LEFT(a,s); \
		a += b; \
	}
#define II(a,b,c,d,x,s,ac) \
	{ \
		a += I(b,c,d) + x + ac; \
		a = ROTATE_LEFT(a,s); \
		a += b; \
	}

void MD5Transform(unsigned int state[4],unsigned char block[64]);
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len);
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len);

unsigned char PADDING[] = {
	0x80,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
};

void MD5Init(MD5_CTX *context) {
	context->count[0] = 0;
	context->count[1] = 0;
	context->state[0] = 0x67452301;
	context->state[1] = 0xEFCDAB89;
	context->state[2] = 0x98BADCFE;
	context->state[3] = 0x10325476;
}
void MD5Update(MD5_CTX *context,unsigned char *input,unsigned int inputlen)
{
	unsigned int i = 0,index = 0,partlen = 0;
	index = (context->count[0] >> 3) & 0x3F;
	partlen = 64 - index;
	context->count[0] += inputlen << 3;
	if(context->count[0] < (inputlen << 3)) {
		context->count[1]++;
	}
	context->count[1] += inputlen >> 29;

	if(inputlen >= partlen) {
		memcpy(&context->buffer[index],input,partlen);
		MD5Transform(context->state,context->buffer);
		for(i = partlen;i+64 <= inputlen;i+=64) {
			MD5Transform(context->state,&input[i]);
		}
		index = 0;
	} else {
		i = 0;
	}
	
	memcpy(&context->buffer[index],&input[i],inputlen-i);
}

void MD5Final(MD5_CTX *context,unsigned char digest[16]) {
	unsigned int index = 0,padlen = 0;
	unsigned char bits[8];
	index = (context->count[0] >> 3) & 0x3F;
	padlen = (index < 56)?(56-index):(120-index);
	MD5Encode(bits,context->count,8);
	MD5Update(context,PADDING,padlen);
	MD5Update(context,bits,8);
	MD5Encode(digest,context->state,16);
}
void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len) {
	unsigned int i = 0,j = 0;
	while(j < len) {
		output[j] = input[i] & 0xFF;
		output[j+1] = (input[i] >> 8) & 0xFF;
		output[j+2] = (input[i] >> 16) & 0xFF;
		output[j+3] = (input[i] >> 24) & 0xFF;
		i++;
		j+=4;
	}
}
void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len) {
	unsigned int i = 0,j = 0;
	while(j < len) {
		output[i] = (input[j]) | (input[j+1] << 8) | (input[j+2] << 16) | (input[j+3] << 24);
		i++;
		j+=4;
	}
}
void MD5Transform(unsigned int state[4],unsigned char block[64]) {
	unsigned int a = state[0];
	unsigned int b = state[1];
	unsigned int c = state[2];
	unsigned int d = state[3];
	unsigned int x[64];

	MD5Decode(x,block,64);

	FF(a, b, c, d, x[ 0], 7, 0xd76aa478);
	FF(d, a, b, c, x[ 1], 12, 0xe8c7b756);
	FF(c, d, a, b, x[ 2], 17, 0x242070db);
	FF(b, c, d, a, x[ 3], 22, 0xc1bdceee);
	FF(a, b, c, d, x[ 4], 7, 0xf57c0faf);
	FF(d, a, b, c, x[ 5], 12, 0x4787c62a);
	FF(c, d, a, b, x[ 6], 17, 0xa8304613);
	FF(b, c, d, a, x[ 7], 22, 0xfd469501);
	FF(a, b, c, d, x[ 8], 7, 0x698098d8);
	FF(d, a, b, c, x[ 9], 12, 0x8b44f7af);
	FF(c, d, a, b, x[10], 17, 0xffff5bb1);
	FF(b, c, d, a, x[11], 22, 0x895cd7be);
	FF(a, b, c, d, x[12], 7, 0x6b901122);
	FF(d, a, b, c, x[13], 12, 0xfd987193);
	FF(c, d, a, b, x[14], 17, 0xa679438e);
	FF(b, c, d, a, x[15], 22, 0x49b40821);

	GG(a, b, c, d, x[ 1], 5, 0xf61e2562);
	GG(d, a, b, c, x[ 6], 9, 0xc040b340);
	GG(c, d, a, b, x[11], 14, 0x265e5a51);
	GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa);
	GG(a, b, c, d, x[ 5], 5, 0xd62f105d);
	GG(d, a, b, c, x[10], 9,  0x2441453);
	GG(c, d, a, b, x[15], 14, 0xd8a1e681);
	GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8);
	GG(a, b, c, d, x[ 9], 5, 0x21e1cde6);
	GG(d, a, b, c, x[14], 9, 0xc33707d6);
	GG(c, d, a, b, x[ 3], 14, 0xf4d50d87);
	GG(b, c, d, a, x[ 8], 20, 0x455a14ed);
	GG(a, b, c, d, x[13], 5, 0xa9e3e905);
	GG(d, a, b, c, x[ 2], 9, 0xfcefa3f8);
	GG(c, d, a, b, x[ 7], 14, 0x676f02d9);
	GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);


	HH(a, b, c, d, x[ 5], 4, 0xfffa3942);
	HH(d, a, b, c, x[ 8], 11, 0x8771f681);
	HH(c, d, a, b, x[11], 16, 0x6d9d6122);
	HH(b, c, d, a, x[14], 23, 0xfde5380c);
	HH(a, b, c, d, x[ 1], 4, 0xa4beea44);
	HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9);
	HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60);
	HH(b, c, d, a, x[10], 23, 0xbebfbc70);
	HH(a, b, c, d, x[13], 4, 0x289b7ec6);
	HH(d, a, b, c, x[ 0], 11, 0xeaa127fa);
	HH(c, d, a, b, x[ 3], 16, 0xd4ef3085);
	HH(b, c, d, a, x[ 6], 23,  0x4881d05);
	HH(a, b, c, d, x[ 9], 4, 0xd9d4d039);
	HH(d, a, b, c, x[12], 11, 0xe6db99e5);
	HH(c, d, a, b, x[15], 16, 0x1fa27cf8);
	HH(b, c, d, a, x[ 2], 23, 0xc4ac5665);


	II(a, b, c, d, x[ 0], 6, 0xf4292244);
	II(d, a, b, c, x[ 7], 10, 0x432aff97);
	II(c, d, a, b, x[14], 15, 0xab9423a7);
	II(b, c, d, a, x[ 5], 21, 0xfc93a039);
	II(a, b, c, d, x[12], 6, 0x655b59c3);
	II(d, a, b, c, x[ 3], 10, 0x8f0ccc92);
	II(c, d, a, b, x[10], 15, 0xffeff47d);
	II(b, c, d, a, x[ 1], 21, 0x85845dd1);
	II(a, b, c, d, x[ 8], 6, 0x6fa87e4f);
	II(d, a, b, c, x[15], 10, 0xfe2ce6e0);
	II(c, d, a, b, x[ 6], 15, 0xa3014314);
	II(b, c, d, a, x[13], 21, 0x4e0811a1);
	II(a, b, c, d, x[ 4], 6, 0xf7537e82);
	II(d, a, b, c, x[11], 10, 0xbd3af235);
	II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb);
	II(b, c, d, a, x[ 9], 21, 0xeb86d391);
	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;
}

int MD5EncryStr(unsigned int *output,unsigned char *input,unsigned int len)
{
	MD5_CTX md5;
	unsigned char md5EndStr[16]={0};

	if(NULL == output || input == NULL)
		return -1;

	MD5Init(&md5);
	MD5Update(&md5, input, len);
	MD5Final(&md5, md5EndStr);

	memcpy(output,md5EndStr,sizeof(md5EndStr));
	return 0;
}

main.c：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include "md5.h"

int main()
{
	int i = 0;
	int nRet = -1;
	int nSize = 0;
	unsigned char MD5ID[16]={0};
	unsigned char *pData ="hello";

	nSize = strlen(pData);
	nRet = MD5EncryStr(MD5ID,pData,nSize);
	if(nRet<0){
		printf("[%s] MD5EncryStr failed,pData=%s,nSize=%d\n",__FUNCTION__,pData,nSize);
		return -1;
	}

	printf("[%s] MD5Encry MD5ID:\n",__FUNCTION__);
	for(i = 0;i<16;i++)
		printf("%x",MD5ID[i]);
	printf("\n");

	return 0;	
}

结果！