#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "md5.c"
int main(int argc, char* argv[])
{
int i
unsigned char encrypt[] = "admin"//21232f297a57a5a743894a0e4a801fc3
unsigned char decrypt[16]
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 = 0i <16i++)
{
printf("%02x", decrypt[i])
}
getchar()
return 0
}
md5.c
#include <memory.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 = partleni + 64 <= inputleni += 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)
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)/* 50 */
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
}
md5.h
#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
题中所示代码中，python实现了计算空字符串的MD5值，并对MD5的值的十六进制的字符串所表示的字节进行BASE64处理。
不像Python内部有实现md5功能，根据ANSI C标准，C语言的标准库里是没有md5功能的；
但是RFC1231规定了MD5功能的C实现并提供了附件，可以直接用，也可以直接获取现成的实现，在编译链接时指定正确的.h头文件和.lib静态链接库文件；
这里我采取前者的做法（电脑上没有装VC，有VC就简单很多，使用的是minGW）大概六七百行代码左右。
然后这里展示不完，给个实现效果图
这是我整理的实现代码，其中BASE64部分使用了github上littlestar的b64.c，然后MD5计算部分直接参考了RFC1231标准的附录。RFC1231文件有计算方法
BASE64的编码原理
#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
源文件md5.c
#include <memory.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 = partleni+64 <= inputleni+=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)
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 */
