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1.简介
MD5即Message-Digest Algorithm 5（信息-摘要算法5），用于确保信息传输完整一致。是计算机广泛使用的杂凑算法之一（又译摘要算法、哈希算法），主流编程语言普遍已有MD5实现。
MD5算法具有以下特点：
1、压缩性：任意长度的数据，算出的MD5值长度都是固定的。
2、容易计算：从原数据计算出MD5值很容易。
3、抗修改性：对原数据进行任何改动，哪怕只修改1个字节，所得到的MD5值都有很大区别。
4、强抗碰撞：已知原数据和其MD5值，想找到一个具有相同MD5值的数据（即伪造数据）是非常困难的。
MD5的作用是让大容量信息在用数字签名软件签署私人密钥前被"压缩"成一种保密的格式（就是把一个任意长度的字节串变换成一定长的16进制数字串）。
大家都知道，地球上任何人都有自己独一无二的指纹，这常常成为司法机关鉴别罪犯身份最值得信赖的方法；与之类似，MD5就可以为任何文件（不管其大小、格式、数量）产生一个同样独一无二的MD5“数字指纹”，如果任何人对文件做了任何改动，其MD5也就是对应的“数字指纹”都会发生变化。
MD5.C
//#include <memory.h>
#include "MD5.h"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); /* 1 */FF(d, a, b, c, x[1], 12, 0xe8c7b756); /* 2 */FF(c, d, a, b, x[2], 17, 0x242070db); /* 3 */FF(b, c, d, a, x[3], 22, 0xc1bdceee); /* 4 */FF(a, b, c, d, x[4], 7, 0xf57c0faf); /* 5 */FF(d, a, b, c, x[5], 12, 0x4787c62a); /* 6 */FF(c, d, a, b, x[6], 17, 0xa8304613); /* 7 */FF(b, c, d, a, x[7], 22, 0xfd469501); /* 8 */FF(a, b, c, d, x[8], 7, 0x698098d8); /* 9 */FF(d, a, b, c, x[9], 12, 0x8b44f7af); /* 10 */FF(c, d, a, b, x[10], 17, 0xffff5bb1); /* 11 */FF(b, c, d, a, x[11], 22, 0x895cd7be); /* 12 */FF(a, b, c, d, x[12], 7, 0x6b901122); /* 13 */FF(d, a, b, c, x[13], 12, 0xfd987193); /* 14 */FF(c, d, a, b, x[14], 17, 0xa679438e); /* 15 */FF(b, c, d, a, x[15], 22, 0x49b40821); /* 16 *//* Round 2 */GG(a, b, c, d, x[1], 5, 0xf61e2562); /* 17 */GG(d, a, b, c, x[6], 9, 0xc040b340); /* 18 */GG(c, d, a, b, x[11], 14, 0x265e5a51); /* 19 */GG(b, c, d, a, x[0], 20, 0xe9b6c7aa); /* 20 */GG(a, b, c, d, x[5], 5, 0xd62f105d); /* 21 */GG(d, a, b, c, x[10], 9, 0x2441453); /* 22 */GG(c, d, a, b, x[15], 14, 0xd8a1e681); /* 23 */GG(b, c, d, a, x[4], 20, 0xe7d3fbc8); /* 24 */GG(a, b, c, d, x[9], 5, 0x21e1cde6); /* 25 */GG(d, a, b, c, x[14], 9, 0xc33707d6); /* 26 */GG(c, d, a, b, x[3], 14, 0xf4d50d87); /* 27 */GG(b, c, d, a, x[8], 20, 0x455a14ed); /* 28 */GG(a, b, c, d, x[13], 5, 0xa9e3e905); /* 29 */GG(d, a, b, c, x[2], 9, 0xfcefa3f8); /* 30 */GG(c, d, a, b, x[7], 14, 0x676f02d9); /* 31 */GG(b, c, d, a, x[12], 20, 0x8d2a4c8a); /* 32 *//* Round 3 */HH(a, b, c, d, x[5], 4, 0xfffa3942); /* 33 */HH(d, a, b, c, x[8], 11, 0x8771f681); /* 34 */HH(c, d, a, b, x[11], 16, 0x6d9d6122); /* 35 */HH(b, c, d, a, x[14], 23, 0xfde5380c); /* 36 */HH(a, b, c, d, x[1], 4, 0xa4beea44); /* 37 */HH(d, a, b, c, x[4], 11, 0x4bdecfa9); /* 38 */HH(c, d, a, b, x[7], 16, 0xf6bb4b60); /* 39 */HH(b, c, d, a, x[10], 23, 0xbebfbc70); /* 40 */HH(a, b, c, d, x[13], 4, 0x289b7ec6); /* 41 */HH(d, a, b, c, x[0], 11, 0xeaa127fa); /* 42 */HH(c, d, a, b, x[3], 16, 0xd4ef3085); /* 43 */HH(b, c, d, a, x[6], 23, 0x4881d05); /* 44 */HH(a, b, c, d, x[9], 4, 0xd9d4d039); /* 45 */HH(d, a, b, c, x[12], 11, 0xe6db99e5); /* 46 */HH(c, d, a, b, x[15], 16, 0x1fa27cf8); /* 47 */HH(b, c, d, a, x[2], 23, 0xc4ac5665); /* 48 *//* Round 4 */II(a, b, c, d, x[0], 6, 0xf4292244); /* 49 */II(d, a, b, c, x[7], 10, 0x432aff97); /* 50 */II(c, d, a, b, x[14], 15, 0xab9423a7); /* 51 */II(b, c, d, a, x[5], 21, 0xfc93a039); /* 52 */II(a, b, c, d, x[12], 6, 0x655b59c3); /* 53 */II(d, a, b, c, x[3], 10, 0x8f0ccc92); /* 54 */II(c, d, a, b, x[10], 15, 0xffeff47d); /* 55 */II(b, c, d, a, x[1], 21, 0x85845dd1); /* 56 */II(a, b, c, d, x[8], 6, 0x6fa87e4f); /* 57 */II(d, a, b, c, x[15], 10, 0xfe2ce6e0); /* 58 */II(c, d, a, b, x[6], 15, 0xa3014314); /* 59 */II(b, c, d, a, x[13], 21, 0x4e0811a1); /* 60 */II(a, b, c, d, x[4], 6, 0xf7537e82); /* 61 */II(d, a, b, c, x[11], 10, 0xbd3af235); /* 62 */II(c, d, a, b, x[2], 15, 0x2ad7d2bb); /* 63 */II(b, c, d, a, x[9], 21, 0xeb86d391); /* 64 */state[0] += a;state[1] += b;state[2] += c;state[3] += d;
}MD5.h
#ifndef MD5_H
#define MD5_Htypedef struct
{unsigned int count[2];unsigned int state[4];unsigned char buffer[64];
}MD5_CTX;#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 MD5Init(MD5_CTX* context);
void MD5Update(MD5_CTX* context, unsigned char* input, unsigned int inputlen);
void MD5Final(MD5_CTX* context, unsigned char digest[16]);
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);#endifmain.c
#include <stdio.h>
#include <stdlib.h>
#include "MD5.h"
#include <string.h>//字符串
void main(void)
{
int read_len;
int i;
char temp[8] = { 0 };
unsigned char digest[16]; //存放结果
char hexbuf[128] = "12334567";
unsigned char decrypt[16] = { 0 };
unsigned char decrypt32[64] = { 0 };//md5:32135a337f8dc8e2bb9a9b80d86bdfd0MD5_CTX md5c;MD5Init(&md5c); //初始化
read_len = strlen(hexbuf);
MD5Update(&md5c, (unsigned char*)hexbuf, read_len);MD5Final(&md5c, decrypt);strcpy((char*)decrypt32, "");for (i = 0; i < 16; i++)
{sprintf(temp, "%02x", decrypt[i]);strcat((char*)decrypt32, temp);}printf("md5:%s\n", decrypt32);return;
}//文件
/*
#include <stdio.h>
#include <stdlib.h>
#include "md5.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>#define FORWORD_FW "123.c"int calc_md5(char* filename, char* dest)
{int i;int filelen = 0;int read_len;char temp[8] = { 0 };char hexbuf[128] = { 0 };unsigned char decrypt[16] = { 0 };unsigned char decrypt32[64] = { 0 };MD5_CTX md5;char fw_path[128];int fdf;fdf = open(filename, O_RDWR);if (fdf < 0){printf("%s not exist\n", FORWORD_FW);return -1;}MD5Init(&md5);while (1){read_len = read(fdf, hexbuf, sizeof(hexbuf));if (read_len < 0) {close(fdf);return -1;}if (read_len == 0){break;}filelen += read_len;MD5Update(&md5, (unsigned char*)hexbuf, read_len);}MD5Final(&md5, decrypt);strcpy((char*)decrypt32, "");for (i = 0; i < 16; i++){sprintf(temp, "%02x", decrypt[i]);strcat((char*)decrypt32, temp);}strcpy(dest, decrypt32);printf("md5:%s len=%d\n", dest, filelen);close(fdf);return filelen;
}
int main(int argc, char* argv[])
{int ret;int filelen;char md5_str[64] = { 0 };char cmd[256] = { 0 };filelen = calc_md5(FORWORD_FW, md5_str);if (filelen < 0){printf("calc_md5 fail\n");return -1;}return 0;
}*/