MD5相信绝大数人都接触过，也有无数人问过我怎么做MD5解密。
当然，我们知道MD5自然没有办法解密，所以解密也不过是大量已知数据做成字典而已，MD5是不可能通过逆向计算解密的。
为什么呢？因为哈希冲突。
举个简单的例子：
比如说我给定10个位置来存放东西，假设我的对应方法是简单的求余%。
那么11%10，21%10的结果就会相同。这样就造成了冲突。
MD5也是如此，我们常用的MD5位数是32位，那么对于不同长度的数据，通过指定算法让他们变成32位，就必然存在这种冲突
这就是MD5无法逆向计算的原因，当然，大部分加密算法目的就是让你不可逆，否则就很难达到真正的安全。
简单说明一下MD5的处理步骤：
MD5以512位分组来处理输入文本，每一分组又划分为16个32位子分组。算法的输出由四个32位分组组成，将它们级联形成一个128位散列值。
①如果输入信息的长度(bit)对512求余的结果不等于448，就需要填充使得对512求余的结果等于448。填充的方法是填充一个1和n个0。填充完后，信息的长度就为N*512+448(bit)
也就是说我们将一组信息分成n个（512位）组，每组的计算都要引入前一组的结果值，这样就保证了所有的文本都参与了实际运算。
②记录信息长度：用64位来存储填充前信息长度。这64位加在第一步结果的后面，这样信息长度就变为N*512+448+64=(N+1)*512位，
这也解释了为什么第一步要求余448，因为要用最后的64位来存储填充信息长度
③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
④处理分组数据
每一分组的算法流程如下：第一分组需要将上面四个链接变量复制到另外四个变量中：A到a，B到b，C到c，D到d。从第二分组开始的变量为上一分组的运算结果，即A = a， B = b， C = c， D = d。主循环有四轮（MD4只有三轮），每轮循环都很相似。第一轮进行16次操作。每次操作对a、b、c和d中的其中三个作一次非线性函数运算，然后将所得结果加上第四个变量，文本的一个子分组和一个常数。再将所得结果向左环移一个不定的数，并加上a、b、c或d中之一。最后用该结果取代a、b、c或d中之一。
⑤输出a、b、c和d的级联。
四轮运算：
第一轮FF(a ,b ,c ,d ,M0 ,7 ,0xd76aa478 )FF(d ,a ,b ,c ,M1 ,12 ,0xe8c7b756 )FF(c ,d ,a ,b ,M2 ,17 ,0x242070db )FF(b ,c ,d ,a ,M3 ,22 ,0xc1bdceee )FF(a ,b ,c ,d ,M4 ,7 ,0xf57c0faf )FF(d ,a ,b ,c ,M5 ,12 ,0x4787c62a )FF(c ,d ,a ,b ,M6 ,17 ,0xa8304613 )FF(b ,c ,d ,a ,M7 ,22 ,0xfd469501)FF(a ,b ,c ,d ,M8 ,7 ,0x698098d8 )FF(d ,a ,b ,c ,M9 ,12 ,0x8b44f7af )FF(c ,d ,a ,b ,M10 ,17 ,0xffff5bb1 )FF(b ,c ,d ,a ,M11 ,22 ,0x895cd7be )FF(a ,b ,c ,d ,M12 ,7 ,0x6b901122 )FF(d ,a ,b ,c ,M13 ,12 ,0xfd987193 )FF(c ,d ,a ,b ,M14 ,17 ,0xa679438e )FF(b ,c ,d ,a ,M15 ,22 ,0x49b40821 )第二轮GG(a ,b ,c ,d ,M1 ,5 ,0xf61e2562 )GG(d ,a ,b ,c ,M6 ,9 ,0xc040b340 )GG(c ,d ,a ,b ,M11 ,14 ,0x265e5a51 )GG(b ,c ,d ,a ,M0 ,20 ,0xe9b6c7aa )GG(a ,b ,c ,d ,M5 ,5 ,0xd62f105d )GG(d ,a ,b ,c ,M10 ,9 ,0x02441453 )GG(c ,d ,a ,b ,M15 ,14 ,0xd8a1e681 )GG(b ,c ,d ,a ,M4 ,20 ,0xe7d3fbc8 )GG(a ,b ,c ,d ,M9 ,5 ,0x21e1cde6 )GG(d ,a ,b ,c ,M14 ,9 ,0xc33707d6 )GG(c ,d ,a ,b ,M3 ,14 ,0xf4d50d87 )GG(b ,c ,d ,a ,M8 ,20 ,0x455a14ed )GG(a ,b ,c ,d ,M13 ,5 ,0xa9e3e905 )GG(d ,a ,b ,c ,M2 ,9 ,0xfcefa3f8 )GG(c ,d ,a ,b ,M7 ,14 ,0x676f02d9 )GG(b ,c ,d ,a ,M12 ,20 ,0x8d2a4c8a )第三轮HH(a ,b ,c ,d ,M5 ,4 ,0xfffa3942 )HH(d ,a ,b ,c ,M8 ,11 ,0x8771f681 )HH(c ,d ,a ,b ,M11 ,16 ,0x6d9d6122 )HH(b ,c ,d ,a ,M14 ,23 ,0xfde5380c )HH(a ,b ,c ,d ,M1 ,4 ,0xa4beea44 )HH(d ,a ,b ,c ,M4 ,11 ,0x4bdecfa9 )HH(c ,d ,a ,b ,M7 ,16 ,0xf6bb4b60 )HH(b ,c ,d ,a ,M10 ,23 ,0xbebfbc70 )HH(a ,b ,c ,d ,M13 ,4 ,0x289b7ec6 )HH(d ,a ,b ,c ,M0 ,11 ,0xeaa127fa )HH(c ,d ,a ,b ,M3 ,16 ,0xd4ef3085 )HH(b ,c ,d ,a ,M6 ,23 ,0x04881d05 )HH(a ,b ,c ,d ,M9 ,4 ,0xd9d4d039 )HH(d ,a ,b ,c ,M12 ,11 ,0xe6db99e5 )HH(c ,d ,a ,b ,M15 ,16 ,0x1fa27cf8 )HH(b ,c ,d ,a ,M2 ,23 ,0xc4ac5665 )第四轮II(a ,b ,c ,d ,M0 ,6 ,0xf4292244 )II(d ,a ,b ,c ,M7 ,10 ,0x432aff97 )II(c ,d ,a ,b ,M14 ,15 ,0xab9423a7 )II(b ,c ,d ,a ,M5 ,21 ,0xfc93a039 )II(a ,b ,c ,d ,M12 ,6 ,0x655b59c3 )II(d ,a ,b ,c ,M3 ,10 ,0x8f0ccc92 )II(c ,d ,a ,b ,M10 ,15 ,0xffeff47d )II(b ,c ,d ,a ,M1 ,21 ,0x85845dd1 )II(a ,b ,c ,d ,M8 ,6 ,0x6fa87e4f )II(d ,a ,b ,c ,M15 ,10 ,0xfe2ce6e0 )II(c ,d ,a ,b ,M6 ,15 ,0xa3014314 )II(b ,c ,d ,a ,M13 ,21 ,0x4e0811a1 )II(a ,b ,c ,d ,M4 ,6 ,0xf7537e82 )II(d ,a ,b ,c ,M11 ,10 ,0xbd3af235 )II(c ,d ,a ,b ,M2 ,15 ,0x2ad7d2bb )II(b ,c ,d ,a ,M9 ,21 ,0xeb86d391 )所有这些完成之后，将a、b、c、d分别在原来基础上再加上A、B、C、D。即a = a + A，b = b + B，c = c + C，d = d + D然后用下一分组数据继续运行以上算法。
完整C++代码
文本加密：
#include <stdio.h> #include <stdlib.h> #include <time.h> #include <string.h> typedef unsigned char *POINTER;typedef unsigned short int UINT2;typedef unsigned long int UINT4;typedef struct {UINT4 state[4];UINT4 count[2];unsigned char buffer[64];} MD5_CTX;void MD5Init(MD5_CTX *);void MD5Update(MD5_CTX *, unsigned char *, unsigned int);void MD5Final(unsigned char [16], MD5_CTX *);#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 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 };#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); } inline void Encode(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);}}inline void Decode(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);}inline void MD5Transform (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);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 */ 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 */ 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 */ 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;memset ((POINTER)x, 0, sizeof (x));}inline void MD5Init(MD5_CTX *context) {context->count[0] = context->count[1] = 0;context->state[0] = 0x67452301;context->state[1] = 0xefcdab89;context->state[2] = 0x98badcfe;context->state[3] = 0x10325476;}inline void MD5Update(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) {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;memcpy((POINTER)&context->buffer[index], (POINTER)&input[i], inputLen-i);}inline void MD5Final(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);memset ((POINTER)context, 0, sizeof (*context));}void MD5Digest(char *pszInput, unsigned long nInputSize, char *pszOutPut) {MD5_CTX context;unsigned int len = strlen (pszInput);MD5Init (&context);MD5Update (&context, (unsigned char *)pszInput, len);MD5Final ((unsigned char *)pszOutPut, &context);}int main() { char szDigest[16];char encrypt[200];while(-1){gets(encrypt);MD5Digest(encrypt,strlen(encrypt),szDigest);int i;for (i=0;i<16;i++)printf ("%02X",(unsigned char)szDigest[i]);printf("\n");}return 0;}文件加密：
#include<stdio.h>#include <stdlib.h> #include <time.h> #include <string.h> #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 RL(x, y) (((x) << (y)) | ((x) >> (32 - (y)))) //x向左循环移y位#define PP(x) (x<<24)|((x<<8)&0xff0000)|((x>>8)&0xff00)|(x>>24) //将x高低位互换,例如PP(aabbccdd)=ddccbbaa#define FF(a, b, c, d, x, s, ac) a = b + (RL((a + F(b,c,d) + x + ac),s))#define GG(a, b, c, d, x, s, ac) a = b + (RL((a + G(b,c,d) + x + ac),s))#define HH(a, b, c, d, x, s, ac) a = b + (RL((a + H(b,c,d) + x + ac),s))#define II(a, b, c, d, x, s, ac) a = b + (RL((a + I(b,c,d) + x + ac),s))unsigned A,B,C,D,a,b,c,d,i,len,flen[2],x[16]; //i临时变量,len文件长,flen[2]为64位二进制表示的文件初始长度char filename[200]; //文件名FILE *fp;void md5() //MD5核心算法,供64轮{a=A,b=B,c=C,d=D;/**//* Round 1 */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, 0x02441453); /**//* 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, 0x04881d05); /**//* 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 */A += a;B += b;C += c;D += d;}main(){while(1){printf("Input file:");gets(filename); //用get函数,避免scanf以空格分割数据,if (filename[0]==34) filename[strlen(filename)-1]=0,strcpy(filename,filename+1); //支持文件拖曳,但会多出双引号,这里是处理多余的双引号if (!strcmp(filename,"exit")) exit(0); //输入exit退出if (!(fp=fopen(filename,"rb"))){printf("Can not open this file!\n"); //以二进制打开文件continue;}fseek(fp, 0, SEEK_END); //文件指针转到文件末尾if((len=ftell(fp))==-1){printf("Sorry! Can not calculate files which larger than 2 GB!\n"); //ftell函数返回long,最大为2GB,超出返回-1fclose(fp);continue;}rewind(fp); //文件指针复位到文件头A=0x67452301,B=0xefcdab89,C=0x98badcfe,D=0x10325476; //初始化链接变量flen[1]=len/0x20000000; //flen单位是bitflen[0]=(len%0x20000000)*8;memset(x,0,64); //初始化x数组为0fread(&x,4,16,fp); //以4字节为一组,读取16组数据for(i=0; i<len/64; i++) //循环运算直至文件结束{md5();memset(x,0,64);fread(&x,4,16,fp);}((char*)x)[len%64]=128; //文件结束补1,补0操作,128二进制即10000000if(len%64>55) md5(),memset(x,0,64);memcpy(x+14,flen,8); //文件末尾加入原文件的bit长度md5();fclose(fp);printf("MD5 Code:%08x%08x%08x%08x\n",PP(A),PP(B),PP(C),PP(D)); //高低位逆反输出}}