MD5算法 C语言 实现

在项目中遇到需使用MD5算法，给大家共享一下。 具体MD5原理在这里不再做摘要，网上随便搜一下就一大把。

无论多长的字串得到的结果都为16字节，而从理论上说不同的字符串是有可能得到相同的MD5结果，要想还原可不是件容易的事情。

 

#include "stdafx.h"
#include
#include "stdlib.h"

 

typedef unsigned long dword;
typedef unsigned char byte;

/* MD5 context. */
typedef struct {
dword state[4]; /* state (ABCD) */
dword count[2]; /* number of bits, modulo 2^64 (lsb first) */
byte buffer[64]; /* input buffer */
} MD5_CTX;

 

 /* Constants for MD5Transform routine. */

#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 (dword [4], unsigned char [64]);
static void Encode (unsigned char *, dword *, unsigned int);
static void Decode (dword *, unsigned char *, unsigned int);
static void MD5_memcpy (byte*, byte*, unsigned int);
static void MD5_memset (byte*, 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
};

/* F, G, H and I are basic MD5 functions.
*/
#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)))

/* ROTATE_LEFT rotates x left n bits.
*/
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
Rotation is separate from addition to prevent recomputation.
*/
#define FF(a, b, c, d, x, s, ac) { \
(a) += F ((b), (c), (d)) + (x) + (dword)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define GG(a, b, c, d, x, s, ac) { \
(a) += G ((b), (c), (d)) + (x) + (dword)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define HH(a, b, c, d, x, s, ac) { \
(a) += H ((b), (c), (d)) + (x) + (dword)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}
#define II(a, b, c, d, x, s, ac) { \
(a) += I ((b), (c), (d)) + (x) + (dword)(ac); \
(a) = ROTATE_LEFT ((a), (s)); \
(a) += (b); \
}

/* MD5 initialization. Begins an MD5 operation, writing a new context.
*/
void MD5Init
(
MD5_CTX *context /* context */
)
{
context->count[0] = context->count[1] = 0;
/* Load magic initialization constants. */

context->state[0] = (dword)0x67452301;
context->state[1] = (dword)0xefcdab89;
context->state[2] = (dword)0x98badcfe;
context->state[3] = (dword)0x10325476;
}

/* MD5 block update operation. Continues an MD5 message-digest
operation, processing another message block, and updating the
context.
*/
void MD5Update
(
MD5_CTX *context, /* context */
unsigned char *input, /* input block */
unsigned int inputLen /* length of input block */
)
{
unsigned int i, index, partLen;

/* Compute number of bytes mod 64 */
index = (unsigned int)((context->count[0] >> 3) & 0x3F);

/* Update number of bits */
if ((context->count[0] += ((dword)inputLen << 3)) < ((dword)inputLen << 3))
context->count[1]++;
context->count[1] += ((dword)inputLen >> 29);

partLen = 64 - index;

/* Transform as many times as possible. */
if (inputLen >= partLen) {
MD5_memcpy ((byte*)&context->buffer[index], (byte*)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;

/* Buffer remaining input */
MD5_memcpy
((byte*)&context->buffer[index], (byte*)&input[i], inputLen-i);
}



/* MD5 finalization. Ends an MD5 message-digest operation, writing the
the message digest and zeroizing the context.
*/
void MD5Final
(
unsigned char digest[16], /* message digest */
MD5_CTX *context /* context */
)
{
unsigned char bits[8];
unsigned int index, padLen;

/* Save number of bits */
Encode (bits, context->count, 8);

/* Pad out to 56 mod 64. */
index = (unsigned int)((context->count[0] >> 3) & 0x3f);
padLen = (index < 56) ? (56 - index) : (120 - index);
MD5Update (context, PADDING, padLen);

/* Append length (before padding) */
MD5Update (context, bits, 8);

/* Store state in digest */
Encode (digest, context->state, 16);

/* Zeroize sensitive information. */
MD5_memset ((byte*)context, 0, sizeof (*context));
}



/* MD5 basic transformation. Transforms state based on block.
*/
static void MD5Transform
(
dword state[4],
unsigned char block[64]
)
{
dword a = state[0], b = state[1], c = state[2], d = state[3], x[16];

Decode (x, block, 64);

/* Round 1 */
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 */

/* Round 2 */
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 */

/* Round 3 */
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 */

/* Round 4 */
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;

/* Zeroize sensitive information. */
MD5_memset ((byte*)x, 0, sizeof (x));
}



/* Encodes input (dword) into output (unsigned char). Assumes len is
a multiple of 4.
*/
static void Encode
(
unsigned char *output,
dword *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);
}
}



/* Decodes input (unsigned char) into output (dword). Assumes len is
a multiple of 4.
*/
static void Decode
(
dword *output,
unsigned char *input,
unsigned int len
)
{
unsigned int i, j;

for (i = 0, j = 0; j < len; i++, j += 4)
output[i] = ((dword)input[j]) | (((dword)input[j+1]) << 8) |
(((dword)input[j+2]) << 16) | (((dword)input[j+3]) << 24);
}



/* Note: Replace "for loop" with standard memcpy if possible.
*/

static void MD5_memcpy
(
byte* output,
byte* input,
unsigned int len
)
{
memcpy( output, input, len );
}



/* Note: Replace "for loop" with standard memset if possible.
*/

static void MD5_memset
(
byte* output,
int value,
unsigned int len
)
{
memset( output, value, len );
}

/* 函数调用实现 */

static MD5_CTX hash_context={0};
static unsigned char hash_result[16]={0};

void main(void)
{
/* ab 187EF4436122D1CC2F40DC2B92F0EBA0 */
/* a 0CC175B9C0F1B6A831C399E269772661 */
/* b 92EB5FFEE6AE2FEC3AD71C777531578F */
/* c 4A8A08F09D37B73795649038408B5F33 */
/* ac E2075474294983E013EE4DD2201C7A73 */
/* bc 5360AF35BDE9EBD8F01F492DC059593C */
/* ca 5435C69ED3BCC5B2E4D580E393E373D3 */
/* cb D0D7FDB6977B26929FB68C6083C0B439 */
/* ba 07159C47EE1B19AE4FB9C40D480856C4 */
/* abcdefghijklmnopqrstuvwxyz C3FCD3D76192E4007DFB496CCA67E13B */
/* ABCDEFGHIJKLMNOPQRSTUVWXYZ 1E097BEA4D87C1741ADBEE7DDF0C259A */
char *pName = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
int len = strlen((char*)pName);

MD5Init (&hash_context);

// 使用一次和多次结果是一样的
// MD5Update (&hash_context, (unsigned char *)pName, len);
while (len>0)
{
/* Perform hash calculation for the latest data-read. */
MD5Update (&hash_context, (byte *) pName, 1);
pName++;
len--;
}
/* 运算结果hash_result */
MD5Final (hash_result, &hash_context);
}