Message Digest Algorithm MD5(中文名爲消息摘要算法第五版)爲計算機安全領域廣泛使用的一種散列函數，用以提供消息的完整性保護。該算法的文件號爲RFC 1321(R.Rivest,MIT Laboratory for Computer Science and RSA Data Security Inc. April 1992)。
MD5即Message-Digest Algorithm 5(信息-摘要算法5)，用於確保信息傳輸完整一致。是計算機廣泛使用的雜湊算法之一(又譯摘要算法、哈希算法)，主流編程語言普遍已有MD5實現。將數據(如漢字)運算爲另一固定長度值，是雜湊算法的基礎原理，MD5的前身有MD2、MD3和MD4。
MD5算法具有以下特點:
1、壓縮性:任意長度的數據，算出的MD5值長度都是固定的。
2、容易計算:從原數據計算出MD5值很容易。
3、抗修改性:對原數據進行任何改動，哪怕只修改1個字節，所得到的MD5值都有很大區別。
4、強抗碰撞:已知原數據和其MD5值，想找到一個具有相同MD5值的數據(即僞造數據)是非常困難的。
MD5的作用是讓大容量信息在用數字簽名軟件簽署私人密鑰前被"壓縮"成一種保密的格式(就是把一個任意長度的字節串變換成一定長的十六進制數字串)。除了MD5以外，其中比較有名的還有sha-1、RIPEMD以及Haval等。
/*****************************************************************************
FileName : md5.c
Function : MD5加密算法
Author : mike
Email : [email protected]
Version : V1.0
Date : 2019-07-12
*****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.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);
//Round 1
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); //5
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;
}
int main(int argc, char *argv[]) //md5函數測試代碼文件
{
int i = 0;
//unsigned char encrypt[] ="admin";//21232f297a57a5a743894a0e4a801fc3
unsigned char decrypt[16];
char len = 0;
//unsigned char encrypt[64] = {0};
unsigned char *encrypt = NULL;
unsigned char encrypt_buf = 0;
MD5_CTX md5;
MD5_START:
MD5Init(&md5);
encrypt = malloc(64);
printf("請輸入需加密的明文（長度不大於64)\n");
len = 0;
encrypt[len] = (unsigned char)getchar();
while (encrypt[len] != '\n' && len < 64) //用getchar()函數接收字符，直到接收到回車符或字符數超過56爲止
{
len ++;
encrypt[len] = (unsigned char)getchar();
if(encrypt[len] == ' ')
{
len --;
}
}
printf("加密前: %d\n",len);
for(i = 0;i < len;i ++)
{
printf("%02X ",encrypt[i] - 0x30);
}
//MD5Update(&md5,encrypt,strlen((int *)encrypt));
MD5Update(&md5,encrypt,len);
MD5Final(&md5,decrypt);
//printf("加密前:%s\n加密後:",encrypt);
printf("加密後:\n");
for(i=0;i<16;i++)
{
printf("%02x",decrypt[i]);
}
printf("\n");
free(encrypt);
memset(decrypt,0,sizeof(decrypt));
goto MD5_START; //重新開始計算
//getchar();
return 0;
}
#ifndef MD5_H
#define MD5_H
typedef 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);
#endif