算法原理
对MD5算法简要的叙述可以为：MD5以512位分组来处理输入的信息，且每一分组又被划分为16个32位子分组，经过了一系列的处理后，算法的输出由四个32位分组组成，将这四个32位分组级联后将生成一个128位散列值。
1.填充
在MD5算法中，首先需要对信息进行填充，使其位长对512求余的结果等于448，并且填充必须进行，即使其位长对512求余的结果等于448。因此，信息的位长（Bits Length）将被扩展至N*512+448，N为一个非负整数，N可以是零。
填充的方法如下：
1) 在信息的后面填充一个1和无数个0，直到满足上面的条件时才停止用0对信息的填充。
2) 在这个结果后面附加一个以64位二进制表示的填充前信息长度（单位为Bit），如果二
进制表示的填充前信息长度超过64位，则取低64位。
经过这两步的处理，信息的位长=N*512+448+64=(N+1）*512，即长度恰好是512的整数倍。这样做的原因是为满足后面处理中对信息长度的要求。
2. 初始化变量
初始的128位值为初试链接变量，这些参数用于第一轮的运算，以大端字节序来表示，他们分别为： A=0x01234567，B=0x89ABCDEF，C=0xFEDCBA98，D=0x76543210。
（每一个变量给出的数值是高字节存于内存低地址，低字节存于内存高地址，即大端字节序。在程序中变量A、B、C、D的值分别为0x67452301，0xEFCDAB89，0x98BADCFE，0x10325476）
3. 处理分组数据
MD5算法原理没有看懂，先备注下！！！
4. 输出
最后的输出是a、b、c和d的级联。
5. 源码
MD5.h
/*
**********************************************************************
** md5.h -- Header file for implementation of MD5 **
** RSA Data Security, Inc. MD5 Message Digest Algorithm **
** Created: 2/17/90 RLR **
** Revised: 12/27/90 SRD,AJ,BSK,JT Reference C version **
** Revised (for MD5): RLR 4/27/91 **
** -- G modified to have y&~z instead of y&z **
** -- FF, GG, HH modified to add in last register done **
** -- Access pattern: round 2 works mod 5, round 3 works mod 3 **
** -- distinct additive constant for each step **
** -- round 4 added, working mod 7 **
**********************************************************************
*/
/*
**********************************************************************
** Copyright (C) 1990, RSA Data Security, Inc. All rights reserved. **
** **
** License to copy and use this software is granted provided that **
** it is identified as the "RSA Data Security, Inc. MD5 Message **
** Digest Algorithm" in all material mentioning or referencing this **
** software or this function. **
** **
** License is also granted to make and use derivative works **
** provided that such works are identified as "derived from the RSA **
** Data Security, Inc. MD5 Message Digest Algorithm" in all **
** material mentioning or referencing the derived work. **
** **
** RSA Data Security, Inc. makes no representations concerning **
** either the merchantability of this software or the suitability **
** of this software for any particular purpose. It is provided "as **
** is" without express or implied warranty of any kind. **
** **
** These notices must be retained in any copies of any part of this **
** documentation and/or software. **
**********************************************************************
*/
#ifndef _MD5_H
#define _MD5_H
/* F, G and H are basic MD5 functions: selection, majority, parity */
#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) + (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); \
}
/* size of test block */
#define TEST_BLOCK_SIZE 1000
/* number of blocks to process */
#define TEST_BLOCKS 10000
/* number of test bytes = TEST_BLOCK_SIZE * TEST_BLOCKS */
static long TEST_BYTES = (long)TEST_BLOCK_SIZE * (long)TEST_BLOCKS;
/* typedef a 32 bit type */
typedef unsigned long int UINT4;
/* Data structure for MD5 (Message Digest) computation */
typedef struct {
UINT4 i[2]; /* number of _bits_ handled mod 2^64 */
UINT4 buf[4]; /* scratch buffer */
unsigned char in[64]; /* input buffer */
unsigned char digest[16]; /* actual digest after Final call */
} MD5_CTX;
static unsigned char PADDING[64] = {
0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
class CMD5
{
public:
CMD5();
~CMD5();
int MDFile(char *filename, unsigned char *outBuf);
void MDString(char *inString, unsigned char *outBuf);
void MDBuf(unsigned char *inBuf, unsigned int inBufLen, unsigned char *outBuf);
private:
void Init(MD5_CTX *mdContext);
void Update(MD5_CTX *mdContext, unsigned char *inBuf, unsigned int inLen);
void Final(MD5_CTX *mdContext);
void MDPrint(MD5_CTX *mdContext);
/* -- include the following line if the md5.h header file is separate -- */
/* #include "md5.h" */
/* forward declaration */
void Transform(UINT4 *buf, UINT4 *in);
void MDFilter();
void MDTimeTrial();
void MDTestSuite();
};
#endif
MD5.cpp
/*
**********************************************************************
** End of md5.c **
******************************* (cut) ********************************
*/
/*
**********************************************************************
** md5driver.c -- sample routines to test **
** RSA Data Security, Inc. MD5 message digest algorithm. **
** Created: 2/16/90 RLR **
** Updated: 1/91 SRD **
**********************************************************************
*/
/*
**********************************************************************
** Copyright (C) 1990, RSA Data Security, Inc. All rights reserved. **
** **
** RSA Data Security, Inc. makes no representations concerning **
** either the merchantability of this software or the suitability **
** of this software for any particular purpose. It is provided "as **
** is" without express or implied warranty of any kind. **
** **
** These notices must be retained in any copies of any part of this **
** documentation and/or software. **
**********************************************************************
*/
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
//#include <sys/types.h>
#include <time.h>
#include <string.h>
#include "md5.h"
CMD5::CMD5()
{
}
CMD5::~CMD5()
{
}
void CMD5::Init(MD5_CTX *mdContext)
{
mdContext->i[0] = mdContext->i[1] = (UINT4)0;
/* Load magic initialization constants.
*/
mdContext->buf[0] = (UINT4)0x67452301;
mdContext->buf[1] = (UINT4)0xefcdab89;
mdContext->buf[2] = (UINT4)0x98badcfe;
mdContext->buf[3] = (UINT4)0x10325476;
}
void CMD5::Update(MD5_CTX *mdContext, unsigned char *inBuf, unsigned int inLen)
{
UINT4 in[16];
int mdi;
unsigned int i, ii;
/* compute number of bytes mod 64 */
mdi = (int)((mdContext->i[0] >> 3) & 0x3F);
/* update number of bits */
if ((mdContext->i[0] + ((UINT4)inLen << 3)) < mdContext->i[0])
mdContext->i[1]++;
mdContext->i[0] += ((UINT4)inLen << 3);
mdContext->i[1] += ((UINT4)inLen >> 29);
while (inLen--)
{
/* add new character to buffer, increment mdi */
mdContext->in[mdi++] = *inBuf++;
/* transform if necessary */
if (mdi == 0x40)
{
for (i = 0, ii = 0; i < 16; i++, ii += 4)
in[i] = (((UINT4)mdContext->in[ii+3]) << 24) |
(((UINT4)mdContext->in[ii+2]) << 16) |
(((UINT4)mdContext->in[ii+1]) << 8) |
((UINT4)mdContext->in[ii]);
Transform(mdContext->buf, &in[0]);
mdi = 0;
}
}
}
void CMD5::Final(MD5_CTX *mdContext)
{
UINT4 in[16];
int mdi;
unsigned int i, ii;
unsigned int padLen;
/* save number of bits */
in[14] = mdContext->i[0];
in[15] = mdContext->i[1];
/* compute number of bytes mod 64 */
mdi = (int)((mdContext->i[0] >> 3) & 0x3F);
/* pad out to 56 mod 64 */
padLen = (mdi < 56) ? (56 - mdi) : (120 - mdi);
Update (mdContext, PADDING, padLen);
/* append length in bits and transform */
for (i = 0, ii = 0; i < 14; i++, ii += 4)
in[i] = (((UINT4)mdContext->in[ii+3]) << 24) |
(((UINT4)mdContext->in[ii+2]) << 16) |
(((UINT4)mdContext->in[ii+1]) << 8) |
((UINT4)mdContext->in[ii]);
Transform (mdContext->buf, in);
/* store buffer in digest */
for (i = 0, ii = 0; i < 4; i++, ii += 4)
{
mdContext->digest[ii] = (unsigned char)(mdContext->buf[i] & 0xFF);
mdContext->digest[ii+1] = (unsigned char)((mdContext->buf[i] >> 8) & 0xFF);
mdContext->digest[ii+2] = (unsigned char)((mdContext->buf[i] >> 16) & 0xFF);
mdContext->digest[ii+3] = (unsigned char)((mdContext->buf[i] >> 24) & 0xFF);
}
}
void CMD5::MDPrint(MD5_CTX *mdContext)
{
//int i;
//for (i = 0; i < 16; i++)
// printf ("%02x ", mdContext->digest[i]);
}
/* Basic MD5 step. Transform buf based on in.
*/
void CMD5::Transform(UINT4 *buf, UINT4 *in)
{
UINT4 a = buf[0], b = buf[1], c = buf[2], d = buf[3];
/* Round 1 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
FF(a, b, c, d, in[ 0], S11, 3614090360); /* 1 */
FF(d, a, b, c, in[ 1], S12, 3905402710); /* 2 */
FF(c, d, a, b, in[ 2], S13, 606105819); /* 3 */
FF(b, c, d, a, in[ 3], S14, 3250441966); /* 4 */
FF(a, b, c, d, in[ 4], S11, 4118548399); /* 5 */
FF(d, a, b, c, in[ 5], S12, 1200080426); /* 6 */
FF(c, d, a, b, in[ 6], S13, 2821735955); /* 7 */
FF(b, c, d, a, in[ 7], S14, 4249261313); /* 8 */
FF(a, b, c, d, in[ 8], S11, 1770035416); /* 9 */
FF(d, a, b, c, in[ 9], S12, 2336552879); /* 10 */
FF(c, d, a, b, in[10], S13, 4294925233); /* 11 */
FF(b, c, d, a, in[11], S14, 2304563134); /* 12 */
FF(a, b, c, d, in[12], S11, 1804603682); /* 13 */
FF(d, a, b, c, in[13], S12, 4254626195); /* 14 */
FF(c, d, a, b, in[14], S13, 2792965006); /* 15 */
FF(b, c, d, a, in[15], S14, 1236535329); /* 16 */
/* Round 2 */
#define S21 5
#define S22 9
#define S23 14
#define S24 20
GG(a, b, c, d, in[ 1], S21, 4129170786); /* 17 */
GG(d, a, b, c, in[ 6], S22, 3225465664); /* 18 */
GG(c, d, a, b, in[11], S23, 643717713); /* 19 */
GG(b, c, d, a, in[ 0], S24, 3921069994); /* 20 */
GG(a, b, c, d, in[ 5], S21, 3593408605); /* 21 */
GG(d, a, b, c, in[10], S22, 38016083); /* 22 */
GG(c, d, a, b, in[15], S23, 3634488961); /* 23 */
GG(b, c, d, a, in[ 4], S24, 3889429448); /* 24 */
GG(a, b, c, d, in[ 9], S21, 568446438); /* 25 */
GG(d, a, b, c, in[14], S22, 3275163606); /* 26 */
GG(c, d, a, b, in[ 3], S23, 4107603335); /* 27 */
GG(b, c, d, a, in[ 8], S24, 1163531501); /* 28 */
GG(a, b, c, d, in[13], S21, 2850285829); /* 29 */
GG(d, a, b, c, in[ 2], S22, 4243563512); /* 30 */
GG(c, d, a, b, in[ 7], S23, 1735328473); /* 31 */
GG(b, c, d, a, in[12], S24, 2368359562); /* 32 */
/* Round 3 */
#define S31 4
#define S32 11
#define S33 16
#define S34 23
HH(a, b, c, d, in[ 5], S31, 4294588738); /* 33 */
HH(d, a, b, c, in[ 8], S32, 2272392833); /* 34 */
HH(c, d, a, b, in[11], S33, 1839030562); /* 35 */
HH(b, c, d, a, in[14], S34, 4259657740); /* 36 */
HH(a, b, c, d, in[ 1], S31, 2763975236); /* 37 */
HH(d, a, b, c, in[ 4], S32, 1272893353); /* 38 */
HH(c, d, a, b, in[ 7], S33, 4139469664); /* 39 */
HH(b, c, d, a, in[10], S34, 3200236656); /* 40 */
HH(a, b, c, d, in[13], S31, 681279174); /* 41 */
HH(d, a, b, c, in[ 0], S32, 3936430074); /* 42 */
HH(c, d, a, b, in[ 3], S33, 3572445317); /* 43 */
HH(b, c, d, a, in[ 6], S34, 76029189); /* 44 */
HH(a, b, c, d, in[ 9], S31, 3654602809); /* 45 */
HH(d, a, b, c, in[12], S32, 3873151461); /* 46 */
HH(c, d, a, b, in[15], S33, 530742520); /* 47 */
HH(b, c, d, a, in[ 2], S34, 3299628645); /* 48 */
/* Round 4 */
#define S41 6
#define S42 10
#define S43 15
#define S44 21
II(a, b, c, d, in[ 0], S41, 4096336452); /* 49 */
II(d, a, b, c, in[ 7], S42, 1126891415); /* 50 */
II(c, d, a, b, in[14], S43, 2878612391); /* 51 */
II(b, c, d, a, in[ 5], S44, 4237533241); /* 52 */
II(a, b, c, d, in[12], S41, 1700485571); /* 53 */
II(d, a, b, c, in[ 3], S42, 2399980690); /* 54 */
II(c, d, a, b, in[10], S43, 4293915773); /* 55 */
II(b, c, d, a, in[ 1], S44, 2240044497); /* 56 */
II(a, b, c, d, in[ 8], S41, 1873313359); /* 57 */
II(d, a, b, c, in[15], S42, 4264355552); /* 58 */
II(c, d, a, b, in[ 6], S43, 2734768916); /* 59 */
II(b, c, d, a, in[13], S44, 1309151649); /* 60 */
II(a, b, c, d, in[ 4], S41, 4149444226); /* 61 */
II(d, a, b, c, in[11], S42, 3174756917); /* 62 */
II(c, d, a, b, in[ 2], S43, 718787259); /* 63 */
II(b, c, d, a, in[ 9], S44, 3951481745); /* 64 */
buf[0] += a;
buf[1] += b;
buf[2] += c;
buf[3] += d;
}
/* A time trial routine, to measure the speed of MD5.
Measures wall time required to digest TEST_BLOCKS * TEST_BLOCK_SIZE
characters.
*/
void CMD5::MDTimeTrial()
{
MD5_CTX mdContext;
time_t endTime, startTime;
unsigned char data[TEST_BLOCK_SIZE];
unsigned int i;
/* initialize test data */
for (i = 0; i < TEST_BLOCK_SIZE; i++)
data[i] = (unsigned char)(i & 0xFF);
/* start timer */
//printf("MD5 time trial. Processing %ld characters...\n", TEST_BYTES);
time(&startTime);
/* digest data in TEST_BLOCK_SIZE byte blocks */
Init(&mdContext);
for (i = TEST_BLOCKS; i > 0; i--)
Update(&mdContext, data, TEST_BLOCK_SIZE);
Final(&mdContext);
/* stop timer, get time difference */
time(&endTime);
MDPrint(&mdContext);
//printf(" is digest of test input.\n");
//printf("Seconds to process test input: %ld\n", (long)(endTime-startTime));
//printf("Characters processed per second: %ld\n", TEST_BYTES/(endTime-startTime));
}
/* Computes the message digest for string inString.
Prints out message digest, a space, the string (in quotes) and a
carriage return.
*/
void CMD5::MDString(char *inString, unsigned char *outBuf)
{
MD5_CTX mdContext;
unsigned int len = strlen(inString);
Init(&mdContext);
Update(&mdContext, (unsigned char *)inString, len);
Final(&mdContext);
MDPrint(&mdContext);
for (int i=0; i<sizeof(mdContext.digest); i++)
{
outBuf[i] = mdContext.digest[i];
}
//printf(" inString: \"%s\" \n\n", inString);
}
/* Computes the message digest for a specified file.
Prints out message digest, a space, the file name, and a carriage
return.
*/
int CMD5::MDFile(char *filename, unsigned char *outBuf)
{
FILE *inFile = fopen (filename, "rb");
MD5_CTX mdContext;
int bytes;
unsigned char data[1024];
if (inFile == NULL)
{
//printf ("%s can't be opened.\n", filename);
return -1;
}
Init(&mdContext);
while ((bytes = fread (data, 1, 1024, inFile)) != 0)
Update(&mdContext, data, bytes);
Final(&mdContext);
for (int i=0; i<sizeof(mdContext.digest); i++)
outBuf[i] = mdContext.digest[i];
//printf(" %s\n", filename);
fclose(inFile);
MDPrint(&mdContext);
return 0;
}
void CMD5::MDBuf(unsigned char *inBuf, unsigned int inBufLen, unsigned char *outBuf)
{
MD5_CTX mdContext;
Init(&mdContext);
Update(&mdContext, inBuf, inBufLen);
Final(&mdContext);
for (int i=0; i<sizeof(mdContext.digest); i++)
outBuf[i] = mdContext.digest[i];
MDPrint(&mdContext);
}
/* Writes the message digest of the data from stdin onto stdout,
followed by a carriage return.
*/
void CMD5::MDFilter()
{
//MD5_CTX mdContext;
//int bytes;
//unsigned char data[16];
//MD5Init(&mdContext);
//while ((bytes = fread (data, 1, 16, stdin)) != 0)
// MD5Update(&mdContext, data, bytes);
//MD5Final(&mdContext);
//MDPrint(&mdContext);
//printf("\n");
}
/* Runs a standard suite of test data.
*/
void CMD5::MDTestSuite()
{
//char outString[35];
//memset(outString, 0, sizeof(outString));
//printf("MD5 test suite results:\n\n");
//MDString("", outString);
//MDString("a", outString);
//char temp[5]= {0x31, 0x32, 0x33 ,0x34, 0};
//MDString(temp, outString);
//MDString("message digest", outString);
//MDString("abcdefghijklmnopqrstuvwxyz", outString);
//MDString("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789", outString);
//MDString("1234567890123456789012345678901234567890\
// 1234567890123456789012345678901234567890", outString);
// /* Contents of file foo are "abc" */
// MDFile ("foo");
}
