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科技改變生活 · 科技引領未來
本文詳細講解視頻如下：
《C語言實現MD5算法》
摘要算法又稱哈希算法。
它表示輸入任意長度的數據，輸出固定長度的數據，它的主要特征是加密過程不需要密鑰，并且經過加密的數據無法被解密。
目前可以被解密逆向的只有CRC32算法，只有輸入相同的明文數據經過相同的消息摘要算法才能得到相同的密文。
消息摘要算法不存在密鑰的管理與分發問題，適合于分布式網絡上使用。由于其加密計算的工作量相當巨大，所以以前的這種算法通常只用于數據量有限的情況下的加密。
這三類算法的主要作用：驗證數據的完整性
MD5即Message-Digest Algorithm 5（信息-摘要算法）。
屬于摘要算法，是一個不可逆過程，就是無論多大數據，經過算法運算后都是生成固定長度的數據，結果使用16進制進行顯示的128bit的二進制串。通常表示為32個十六進制數連成的字符串。
MD5有什么用？
用于確保信息傳輸完整一致。是計算機廣泛使用的雜湊算法之一（又譯摘要算法、哈希算法），主流編程語言普遍已有MD5實現。更多用在文檔校驗上，用來生成密鑰檢測文檔是否被篡改。
有很多在線進行MD5加密的網站，如下：
http://www.metools.info/code/c26.html
舉例: 給字符串 12334567 加密成。
如圖結果為：
32135A337F8DC8E2BB9A9B80D86BDFD0
源文件如下：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
md5.c
include
include &34;md5.h&34;
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 = partlen;i+64 <= inputlen;i+=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);
FF(d, a, b, c, x[ 1], 12, 0xe8c7b756);
FF(c, d, a, b, x[ 2], 17, 0x242070db);
FF(b, c, d, a, x[ 3], 22, 0xc1bdceee);
FF(a, b, c, d, x[ 4], 7, 0xf57c0faf);
FF(d, a, b, c, x[ 5], 12, 0x4787c62a);
FF(c, d, a, b, x[ 6], 17, 0xa8304613);
FF(b, c, d, a, x[ 7], 22, 0xfd469501);
FF(a, b, c, d, x[ 8], 7, 0x698098d8);
FF(d, a, b, c, x[ 9], 12, 0x8b44f7af);
FF(c, d, a, b, x[10], 17, 0xffff5bb1);
FF(b, c, d, a, x[11], 22, 0x895cd7be);
FF(a, b, c, d, x[12], 7, 0x6b901122);
FF(d, a, b, c, x[13], 12, 0xfd987193);
FF(c, d, a, b, x[14], 17, 0xa679438e);
FF(b, c, d, a, x[15], 22, 0x49b40821);
GG(a, b, c, d, x[ 1], 5, 0xf61e2562);
GG(d, a, b, c, x[ 6], 9, 0xc040b340);
GG(c, d, a, b, x[11], 14, 0x265e5a51);
GG(b, c, d, a, x[ 0], 20, 0xe9b6c7aa);
GG(a, b, c, d, x[ 5], 5, 0xd62f105d);
GG(d, a, b, c, x[10], 9, 0x2441453);
GG(c, d, a, b, x[15], 14, 0xd8a1e681);
GG(b, c, d, a, x[ 4], 20, 0xe7d3fbc8);
GG(a, b, c, d, x[ 9], 5, 0x21e1cde6);
GG(d, a, b, c, x[14], 9, 0xc33707d6);
GG(c, d, a, b, x[ 3], 14, 0xf4d50d87);
GG(b, c, d, a, x[ 8], 20, 0x455a14ed);
GG(a, b, c, d, x[13], 5, 0xa9e3e905);
GG(d, a, b, c, x[ 2], 9, 0xfcefa3f8);
GG(c, d, a, b, x[ 7], 14, 0x676f02d9);
GG(b, c, d, a, x[12], 20, 0x8d2a4c8a);
HH(a, b, c, d, x[ 5], 4, 0xfffa3942);
HH(d, a, b, c, x[ 8], 11, 0x8771f681);
HH(c, d, a, b, x[11], 16, 0x6d9d6122);
HH(b, c, d, a, x[14], 23, 0xfde5380c);
HH(a, b, c, d, x[ 1], 4, 0xa4beea44);
HH(d, a, b, c, x[ 4], 11, 0x4bdecfa9);
HH(c, d, a, b, x[ 7], 16, 0xf6bb4b60);
HH(b, c, d, a, x[10], 23, 0xbebfbc70);
HH(a, b, c, d, x[13], 4, 0x289b7ec6);
HH(d, a, b, c, x[ 0], 11, 0xeaa127fa);
HH(c, d, a, b, x[ 3], 16, 0xd4ef3085);
HH(b, c, d, a, x[ 6], 23, 0x4881d05);
HH(a, b, c, d, x[ 9], 4, 0xd9d4d039);
HH(d, a, b, c, x[12], 11, 0xe6db99e5);
HH(c, d, a, b, x[15], 16, 0x1fa27cf8);
HH(b, c, d, a, x[ 2], 23, 0xc4ac5665);
II(a, b, c, d, x[ 0], 6, 0xf4292244);
II(d, a, b, c, x[ 7], 10, 0x432aff97);
II(c, d, a, b, x[14], 15, 0xab9423a7);
II(b, c, d, a, x[ 5], 21, 0xfc93a039);
II(a, b, c, d, x[12], 6, 0x655b59c3);
II(d, a, b, c, x[ 3], 10, 0x8f0ccc92);
II(c, d, a, b, x[10], 15, 0xffeff47d);
II(b, c, d, a, x[ 1], 21, 0x85845dd1);
II(a, b, c, d, x[ 8], 6, 0x6fa87e4f);
II(d, a, b, c, x[15], 10, 0xfe2ce6e0);
II(c, d, a, b, x[ 6], 15, 0xa3014314);
II(b, c, d, a, x[13], 21, 0x4e0811a1);
II(a, b, c, d, x[ 4], 6, 0xf7537e82);
II(d, a, b, c, x[11], 10, 0xbd3af235);
II(c, d, a, b, x[ 2], 15, 0x2ad7d2bb);
II(b, c, d, a, x[ 9], 21, 0xeb86d391);
state[0] += a;
state[1] += b;
state[2] += c;
state[3] += d;
}
MD5加密步驟如下：
MD5_CTX md5c;
MD5Init(MD5_CTX *context);
實現MD5值的計算及結構體的更新：
MD5Update(MD5_CTX *context,(unsigned char *)input,inputLen);
MD5Final(MD5_CTX *context,unsigned char digest[16]);
轉換成32位的16進制字符串。
對字符串進行加密：
1 include
2 include
3 include &34;md5.h&34;
4 include
5 include
6 include
7 include
8
9 void main( void )
10 {
11 int read_len;
12 int i ;
13 char temp[8]={0};
14 unsigned char digest[16]; //存放結果
15 char hexbuf[128]=&34;12334567&34;;
16 unsigned char decrypt[16]={0};
17 unsigned char decrypt32[64]={0};
18
19 MD5_CTX md5c;
20
21 MD5Init(&md5c); //初始化
22 read_len = strlen(hexbuf);
23 MD5Update(&md5c,(unsigned char *)hexbuf,read_len);
24
25 MD5Final(&md5c,decrypt);
26 strcpy((char *)decrypt32,&34;&34;);
27
28 for(i=0;i<16;i++)
29 {
30 sprintf(temp,&34;%02x&34;,decrypt[i]);
31 strcat((char *)decrypt32,temp);
32 }
33 printf(&34;md5:%sn&34;,decrypt32);
34
35 return;
36 }
執行結果如下：
本例對字符串12334567進行加密，結果和在線加密結果一致。
對文件進行加密
include
include
include &34;md5.h&34;
include
include
include
include
define FORWORD_FW &34;123.c&34;
int calc_md5(char*filename,char*dest)
{
int i;
int filelen = 0;
int read_len;
char temp[8]={0};
char hexbuf[128]={0};
unsigned char decrypt[16]={0};
unsigned char decrypt32[64]={0};
MD5_CTX md5;
char fw_path[128];
int fdf;
fdf = open(filename,O_RDWR);
if(fdf<0)
{
printf(&34;%s not existn&34;,FORWORD_FW);
return -1;
}
MD5Init(&md5);
while(1)
{
read_len = read(fdf, hexbuf,sizeof(hexbuf));
if (read_len <0) {
close(fdf);
return -1;
}
if(read_len==0)
{
break;
}
filelen += read_len;
MD5Update(&md5,(unsigned char *)hexbuf,read_len);
}
MD5Final(&md5,decrypt);
strcpy((char *)decrypt32,&34;&34;);
for(i=0;i<16;i++)
{
sprintf(temp,&34;%02x&34;,decrypt[i]);
strcat((char *)decrypt32,temp);
}
strcpy(dest,decrypt32);
printf(&34;md5:%s len=%dn&34;,dest,filelen);
close(fdf);
return filelen;
}
int main(int argc, char *argv[])
{
int ret;
int filelen;
char md5_str[64]={0};
char cmd[256]={0};
filelen = calc_md5(FORWORD_FW,md5_str);
if(filelen<0)
{
printf(&34;calc_md5 failn&34;);
return -1;
}
return 0;
}
運行結果：
在線驗證結果對比：
http://www.metools.info/other/o21.html
結果
丁楠明