MD5摘要算法实现

网上找到的实现md5函数代码，包括一个头文件md5.h和一个源文件md5.c，用下面的测试代码test.c测试通过，各文件依次如下：

头文件md5.h：

 #ifndef MD5_H
 #define MD5_H

 typedef struct
 {
     unsigned int count[];
     unsigned int state[];
     unsigned char buffer[];
 }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[]);
 void MD5Transform(unsigned int state[],unsigned char block[]);
 void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len);
 void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len);

 #endif

源文件md5.c：

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

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

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

     if(inputlen >= partlen)
     {
        memcpy(&context->buffer[index],input,partlen);
        MD5Transform(context->state,context->buffer);
        for(i = partlen;i+ <= inputlen;i+=)
            MD5Transform(context->state,&input[i]);
        index = ;
     }
     else
     {
         i = ;
     }
     memcpy(&context->buffer[index],&input[i],inputlen-i);
 }
 void MD5Final(MD5_CTX *context,unsigned char digest[])
 {
     unsigned int index = ,padlen = ;
     unsigned char bits[];
     index = (context->count[] >> ) & 0x3F;
     padlen = (index < )?(-index):(-index);
     MD5Encode(bits,context->count,);
     MD5Update(context,PADDING,padlen);
     MD5Update(context,bits,);
     MD5Encode(digest,context->state,);
 }
 void MD5Encode(unsigned char *output,unsigned int *input,unsigned int len)
 {
     unsigned int i = ,j = ;
     while(j < len)
     {
          output[j] = input[i] & 0xFF;
          output[j+] = (input[i] >> ) & 0xFF;
          output[j+] = (input[i] >> ) & 0xFF;
          output[j+] = (input[i] >> ) & 0xFF;
          i++;
          j+=;
     }
 }
 void MD5Decode(unsigned int *output,unsigned char *input,unsigned int len)
 {
      unsigned int i = ,j = ;
      while(j < len)
      {
            output[i] = (input[j]) |
                        (input[j+] << ) |
                        (input[j+] << ) |
                        (input[j+] << );
            i++;
            j+=;
      }
 }
 void MD5Transform(unsigned int state[],unsigned char block[])
 {
      unsigned int a = state[];
      unsigned int b = state[];
      unsigned int c = state[];
      unsigned int d = state[];
      unsigned int x[];
      MD5Decode(x,block,);
      FF(a, b, c, d, x[ ], , 0xd76aa478); /* 1 */
  FF(d, a, b, c, x[ ], , 0xe8c7b756); /* 2 */
  FF(c, d, a, b, x[ ], , 0x242070db); /* 3 */
  FF(b, c, d, a, x[ ], , 0xc1bdceee); /* 4 */
  FF(a, b, c, d, x[ ], , 0xf57c0faf); /* 5 */
  FF(d, a, b, c, x[ ], , 0x4787c62a); /* 6 */
  FF(c, d, a, b, x[ ], , 0xa8304613); /* 7 */
  FF(b, c, d, a, x[ ], , 0xfd469501); /* 8 */
  FF(a, b, c, d, x[ ], , 0x698098d8); /* 9 */
  FF(d, a, b, c, x[ ], , 0x8b44f7af); /* 10 */
  FF(c, d, a, b, x[], , 0xffff5bb1); /* 11 */
  FF(b, c, d, a, x[], , 0x895cd7be); /* 12 */
  FF(a, b, c, d, x[], , 0x6b901122); /* 13 */
  FF(d, a, b, c, x[], , 0xfd987193); /* 14 */
  FF(c, d, a, b, x[], , 0xa679438e); /* 15 */
  FF(b, c, d, a, x[], , 0x49b40821); /* 16 */

  /* Round 2 */
  GG(a, b, c, d, x[ ], , 0xf61e2562); /* 17 */
  GG(d, a, b, c, x[ ], , 0xc040b340); /* 18 */
  GG(c, d, a, b, x[], , 0x265e5a51); /* 19 */
  GG(b, c, d, a, x[ ], , 0xe9b6c7aa); /* 20 */
  GG(a, b, c, d, x[ ], , 0xd62f105d); /* 21 */
  GG(d, a, b, c, x[], ,  0x2441453); /* 22 */
  GG(c, d, a, b, x[], , 0xd8a1e681); /* 23 */
  GG(b, c, d, a, x[ ], , 0xe7d3fbc8); /* 24 */
  GG(a, b, c, d, x[ ], , 0x21e1cde6); /* 25 */
  GG(d, a, b, c, x[], , 0xc33707d6); /* 26 */
  GG(c, d, a, b, x[ ], , 0xf4d50d87); /* 27 */
  GG(b, c, d, a, x[ ], , 0x455a14ed); /* 28 */
  GG(a, b, c, d, x[], , 0xa9e3e905); /* 29 */
  GG(d, a, b, c, x[ ], , 0xfcefa3f8); /* 30 */
  GG(c, d, a, b, x[ ], , 0x676f02d9); /* 31 */
  GG(b, c, d, a, x[], , 0x8d2a4c8a); /* 32 */

  /* Round 3 */
  HH(a, b, c, d, x[ ], , 0xfffa3942); /* 33 */
  HH(d, a, b, c, x[ ], , 0x8771f681); /* 34 */
  HH(c, d, a, b, x[], , 0x6d9d6122); /* 35 */
  HH(b, c, d, a, x[], , 0xfde5380c); /* 36 */
  HH(a, b, c, d, x[ ], , 0xa4beea44); /* 37 */
  HH(d, a, b, c, x[ ], , 0x4bdecfa9); /* 38 */
  HH(c, d, a, b, x[ ], , 0xf6bb4b60); /* 39 */
  HH(b, c, d, a, x[], , 0xbebfbc70); /* 40 */
  HH(a, b, c, d, x[], , 0x289b7ec6); /* 41 */
  HH(d, a, b, c, x[ ], , 0xeaa127fa); /* 42 */
  HH(c, d, a, b, x[ ], , 0xd4ef3085); /* 43 */
  HH(b, c, d, a, x[ ], ,  0x4881d05); /* 44 */
  HH(a, b, c, d, x[ ], , 0xd9d4d039); /* 45 */
  HH(d, a, b, c, x[], , 0xe6db99e5); /* 46 */
  HH(c, d, a, b, x[], , 0x1fa27cf8); /* 47 */
  HH(b, c, d, a, x[ ], , 0xc4ac5665); /* 48 */

  /* Round 4 */
  II(a, b, c, d, x[ ], , 0xf4292244); /* 49 */
  II(d, a, b, c, x[ ], , 0x432aff97); /* 50 */
  II(c, d, a, b, x[], , 0xab9423a7); /* 51 */
  II(b, c, d, a, x[ ], , 0xfc93a039); /* 52 */
  II(a, b, c, d, x[], , 0x655b59c3); /* 53 */
  II(d, a, b, c, x[ ], , 0x8f0ccc92); /* 54 */
  II(c, d, a, b, x[], , 0xffeff47d); /* 55 */
  II(b, c, d, a, x[ ], , 0x85845dd1); /* 56 */
  II(a, b, c, d, x[ ], , 0x6fa87e4f); /* 57 */
  II(d, a, b, c, x[], , 0xfe2ce6e0); /* 58 */
  II(c, d, a, b, x[ ], , 0xa3014314); /* 59 */
  II(b, c, d, a, x[], , 0x4e0811a1); /* 60 */
  II(a, b, c, d, x[ ], , 0xf7537e82); /* 61 */
  II(d, a, b, c, x[], , 0xbd3af235); /* 62 */
  II(c, d, a, b, x[ ], , 0x2ad7d2bb); /* 63 */
  II(b, c, d, a, x[ ], , 0xeb86d391); /* 64 */
      state[] += a;
      state[] += b;
      state[] += c;
      state[] += d;
 }

测试代码test.c：

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

 int main(int argc, char *argv[])
 {
     int i;
     unsigned char encrypt[] ="admin";//21232f297a57a5a743894a0e4a801fc3
     unsigned char decrypt[];
     MD5_CTX md5;
     MD5Init(&md5);
     MD5Update(&md5,encrypt,strlen((char *)encrypt));
     MD5Final(&md5,decrypt);
     printf("加密前:%s\n加密后:",encrypt);
     for(i=;i<;i++)
     {
         printf("%02x",decrypt[i]);
     }

     getchar();

     return ;
 }