MD5的算法(C)

MD5的算法描述：

 第一步：增加填充

增加padding使得数据长度（bit为单位）模512为448。如果数据长度正好是模512为448，增加512个填充bit，也就是说填充的个数为1-512。第一个bit为1，其余全部为0。

第二步：补足长度

将数据长度转换为64bit的数值，如果长度超过64bit所能表示的数据长度的范围，值保留最后64bit，增加到前面填充的数据后面，使得最后的数据为512bit的整数倍。也就是32bit的16倍的整数倍。在RFC1321中，32bit称为一个word。

第三步：初始化变量：

用到4个变量，分别为A、B、C、D，均为32bit长。初始化为：

A: 01 23 45 67

B: 89 ab cd ef

C: fe dc ba 98

D: 76 54 32 10

第四步：数据处理：

首先定义4个辅助函数：

F(X,Y,Z) = XY v not(X) Z

G(X,Y,Z) = XZ v Y not(Z)

H(X,Y,Z) = X xor Y xor Z

I(X,Y,Z) = Y xor (X v not(Z))

其中：XY表示按位与，X v Y表示按位或，not(X)表示按位取反。xor表示按位异或。

函数中的X、Y、Z均为32bit。

定义一个需要用到的数组：T(i),i取值1-64,T(i)等于abs(sin(i))的4294967296倍的整数部分,i为弧度。

假设前三步处理后的数据长度为32*16*Nbit

第五步：输出：

最后得到的ABCD为输出结果，共128bit。A为低位，D为高位。

 

MD5算法在编程中的实现：

 

下面来看看如何在C,Delphi和VB中实现MD5算法

C语言举例：

--------------------------------------------

 

*/

#ifndef PROTOTYPES

#define PROTOTYPES 0

#endif

typedef unsigned char *POINTER;

typedef unsigned short int UINT2;

typedef unsigned long int UINT4;

#if PROTOTYPES

#define PROTO_LIST(list) list

#else

#define PROTO_LIST(list) ()

#endif

 

---------- MD5.h----------------------------

 

typedef struct {

  UINT4 state[4];        

  UINT4 count[2];      

  unsigned char buffer[64];                      

} MD5_CTX;

 

void MD5Init PROTO_LIST ((MD5_CTX *));

void MD5Update PROTO_LIST

  ((MD5_CTX *, unsigned char *, unsigned int));

void MD5Final PROTO_LIST ((unsigned char [16], MD5_CTX *));

 

※※※※※※※※※MD5C.C※※※※※※※※※※※※※※※※※※※※※※※※

#include "global.h"

#include "md5.h"

#define S11 7

#define S12 12

#define S13 17

#define S14 22

#define S21 5

#define S22 9

#define S23 14

#define S24 20

#define S31 4

#define S32 11

#define S33 16

#define S34 23

#define S41 6

#define S42 10

#define S43 15

#define S44 21

 

static void MD5Transform PROTO_LIST ((UINT4 [4], unsigned char [64]));

static void Encode PROTO_LIST

  ((unsigned char *, UINT4 *, unsigned int));

static void Decode PROTO_LIST

  ((UINT4 *, unsigned char *, unsigned int));

static void MD5_memcpy PROTO_LIST ((POINTER, POINTER, unsigned int));

static void MD5_memset PROTO_LIST ((POINTER, int, unsigned int));

 

static unsigned char PADDING[64] = {

  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

};

 

/* 定义F G H I 为四个基数

 

#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) + (UINT4)(ac); \

 (a) = ROTATE_LEFT ((a), (s)); \

 (a) += (b); \

  }

#define GG(a, b, c, d, x, s, ac) { \

 (a) += G ((b), (c), (d)) + (x) + (UINT4)(ac); \

 (a) = ROTATE_LEFT ((a), (s)); \

 (a) += (b); \

  }

#define HH(a, b, c, d, x, s, ac) { \

 (a) += H ((b), (c), (d)) + (x) + (UINT4)(ac); \

 (a) = ROTATE_LEFT ((a), (s)); \

 (a) += (b); \

  }

#define II(a, b, c, d, x, s, ac) { \

 (a) += I ((b), (c), (d)) + (x) + (UINT4)(ac); \

 (a) = ROTATE_LEFT ((a), (s)); \

 (a) += (b); \

  }

 

/*开始进行MD5计算

void MD5Init (context)

MD5_CTX *context;                             

{

  context->count[0] = context->count[1] = 0;

  /* 在这里定义四个常数，也就是我们刚才讲到的四个特征数.

 

  context->state[0] = 0x67452301;

  context->state[1] = 0xefcdab89;

  context->state[2] = 0x98badcfe;

  context->state[3] = 0x10325476;

}

 

void MD5Update (context, input, inputLen)

MD5_CTX *context;                               

unsigned char *input;                           

unsigned int inputLen;                  

{

  unsigned int i, index, partLen;

 

  index = (unsigned int)((context->count[0] >> 3) & 0x3F);

 

  if ((context->count[0] += ((UINT4)inputLen << 3)) < ((UINT4)inputLen << 3))

 context->count[1]++;

  context->count[1] += ((UINT4)inputLen >> 29);

 

  partLen = 64 - index;

 

  if (inputLen >= partLen) {

 MD5_memcpy

   ((POINTER)&context->buffer[index], (POINTER)input, partLen);

 MD5Transform (context->state, context->buffer);

 

 for (i = partLen; i + 63 < inputLen; i += 64)

   MD5Transform (context->state, &input[i]);

 

 index = 0;

  }

  else

 i = 0;

 

  MD5_memcpy

 ((POINTER)&context->buffer[index], (POINTER)&input[i],

  inputLen-i);

}

 

void MD5Final (digest, context)

unsigned char digest[16];                 

MD5_CTX *context;                              

{

  unsigned char bits[8];

  unsigned int index, padLen;

 

  Encode (bits, context->count, 8);

 

  index = (unsigned int)((context->count[0] >> 3) & 0x3f);

  padLen = (index < 56) ? (56 - index) : (120 - index);

  MD5Update (context, PADDING, padLen);

  MD5Update (context, bits, 8);

 

  Encode (digest, context->state, 16);

  MD5_memset ((POINTER)context, 0, sizeof (*context));

}

 

static void MD5Transform (state, block)

UINT4 state[4];

unsigned char block[64];

{

  UINT4 a = state[0], b = state[1], c = state[2], d = state[3], x[16];

 

  Decode (x, block, 64);

 

  /* 第一轮循环 */

  FF (a, b, c, d, x[ 0], S11, 0xd76aa478); /* 1 */

  FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); /* 2 */

  FF (c, d, a, b, x[ 2], S13, 0x242070db); /* 3 */

  FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); /* 4 */

  FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); /* 5 */

  FF (d, a, b, c, x[ 5], S12, 0x4787c62a); /* 6 */

  FF (c, d, a, b, x[ 6], S13, 0xa8304613); /* 7 */

  FF (b, c, d, a, x[ 7], S14, 0xfd469501); /* 8 */

  FF (a, b, c, d, x[ 8], S11, 0x698098d8); /* 9 */

  FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); /* 10 */

  FF (c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */

  FF (b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */

  FF (a, b, c, d, x[12], S11, 0x6b901122); /* 13 */

  FF (d, a, b, c, x[13], S12, 0xfd987193); /* 14 */

  FF (c, d, a, b, x[14], S13, 0xa679438e); /* 15 */

  FF (b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

 

 /* 第二轮循环 */

  GG (a, b, c, d, x[ 1], S21, 0xf61e2562); /* 17 */

  GG (d, a, b, c, x[ 6], S22, 0xc040b340); /* 18 */

  GG (c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */

  GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); /* 20 */

  GG (a, b, c, d, x[ 5], S21, 0xd62f105d); /* 21 */

  GG (d, a, b, c, x[10], S22,  0x2441453); /* 22 */

  GG (c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */

  GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); /* 24 */

  GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); /* 25 */

  GG (d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */

  GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); /* 27 */

  GG (b, c, d, a, x[ 8], S24, 0x455a14ed); /* 28 */

  GG (a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */

  GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); /* 30 */

  GG (c, d, a, b, x[ 7], S23, 0x676f02d9); /* 31 */

  GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

 

  /* 第三轮循环 */

  HH (a, b, c, d, x[ 5], S31, 0xfffa3942); /* 33 */

  HH (d, a, b, c, x[ 8], S32, 0x8771f681); /* 34 */

  HH (c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */

  HH (b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */

  HH (a, b, c, d, x[ 1], S31, 0xa4beea44); /* 37 */

  HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); /* 38 */

  HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); /* 39 */

  HH (b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */

  HH (a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */

  HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); /* 42 */

  HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); /* 43 */

  HH (b, c, d, a, x[ 6], S34,  0x4881d05); /* 44 */

  HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); /* 45 */

  HH (d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */

  HH (c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */

  HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); /* 48 */

 

  /* 第四轮循环 */

  II (a, b, c, d, x[ 0], S41, 0xf4292244); /* 49 */

  II (d, a, b, c, x[ 7], S42, 0x432aff97); /* 50 */

  II (c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */

  II (b, c, d, a, x[ 5], S44, 0xfc93a039); /* 52 */

  II (a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */

  II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); /* 54 */

  II (c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */

  II (b, c, d, a, x[ 1], S44, 0x85845dd1); /* 56 */

  II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); /* 57 */

  II (d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */

  II (c, d, a, b, x[ 6], S43, 0xa3014314); /* 59 */

  II (b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */

  II (a, b, c, d, x[ 4], S41, 0xf7537e82); /* 61 */

  II (d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */

  II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); /* 63 */

  II (b, c, d, a, x[ 9], S44, 0xeb86d391); /* 64 */

 

  state[0] += a;

  state[1] += b;

  state[2] += c;

  state[3] += d;

 

  MD5_memset ((POINTER)x, 0, sizeof (x));

 

}

static void Encode (output, input, len)

unsigned char *output;

UINT4 *input;

unsigned int len;

{

  unsigned int i, j;

 

  for (i = 0, j = 0; j < len; i++, j += 4) {

 output[j] = (unsigned char)(input[i] & 0xff);

 output[j+1] = (unsigned char)((input[i] >> 8) & 0xff);

 output[j+2] = (unsigned char)((input[i] >> 16) & 0xff);

 output[j+3] = (unsigned char)((input[i] >> 24) & 0xff);

  }

}

 

static void Decode (output, input, len)

UINT4 *output;

unsigned char *input;

unsigned int len;

{

  unsigned int i, j;

 

  for (i = 0, j = 0; j < len; i++, j += 4)

 output[i] = ((UINT4)input[j]) | (((UINT4)input[j+1]) << 8) |

   (((UINT4)input[j+2]) << 16) | (((UINT4)input[j+3]) << 24);

}

 

static void MD5_memcpy (output, input, len)

POINTER output;

POINTER input;

unsigned int len;

{

  unsigned int i;

 

  for (i = 0; i < len; i++) output[i] = input[i];

}

 

static void MD5_memset (output, value, len)

POINTER output;

int value;

unsigned int len;

{

  unsigned int i;

 

  for (i = 0; i < len; i++)

 ((char *)output)[i] = (char)value;

}