C++实现md5加密或计算文件的唯一性识别

由于网络上传了很多关于C++实现md5加密的类，至于那个是原创，我不敢妄加猜测，只是这里我声明我是转载的，并支持原创。

对于md5加密算法，我提供两文件：

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#ifndef MD5_H

#define MD5_H



#include <string>

#include <fstream>



/* Type define */

typedef unsigned char byte;

typedef unsigned int uint32;



using std::string;

using std::ifstream;



/* MD5 declaration. */

class MD5 {

public:

MD5();

MD5(const void* input, size_t length);

MD5(const string& str);

MD5(ifstream& in);

void update(const void* input, size_t length);

void update(const string& str);

void update(ifstream& in);

const byte* digest();

string toString();

void reset();

string ToMD5(const string& str);//如此，只需调用该函数便完成加密过程



private:

void update(const byte* input, size_t length);

void final();

void transform(const byte block[64]);

void encode(const uint32* input, byte* output, size_t length);

void decode(const byte* input, uint32* output, size_t length);

string bytesToHexString(const byte* input, size_t length);





/* class uncopyable */

MD5(const MD5&);

MD5& operator=(const MD5&);



private:

uint32 _state[4]; /* state (ABCD) */

uint32 _count[2]; /* number of bits, modulo 2^64 (low-order word first) */

byte _buffer[64]; /* input buffer */

byte _digest[16]; /* message digest */

bool _finished; /* calculate finished ? */



static const byte PADDING[64]; /* padding for calculate */

static const char HEX[16];

enum { BUFFER_SIZE = 1024 };

};



#endif /*MD5_H*/

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#include "md5.h"

#include "string.h"

const string MD5_Key="wow";

using namespace std;



/* 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





/* 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) + 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); }





const byte MD5::PADDING[64] = { 0x80 };

const char MD5::HEX[16] = {

'0', '1', '2', '3',

'4', '5', '6', '7',

'8', '9', 'a', 'b',

'c', 'd', 'e', 'f'

};





/* Default construct. */

MD5::MD5() {

reset();

}



/* Construct a MD5 object with a input buffer. */

MD5::MD5(const void* input, size_t length) {

reset();

update(input, length);

}



/* Construct a MD5 object with a string. */

MD5::MD5(const string& str) {

reset();

update(str);

}



/* Construct a MD5 object with a file. */

MD5::MD5(ifstream& in) {

reset();

update(in);

}



/* Return the message-digest */

const byte* MD5::digest() {



if (!_finished) {

_finished = true;

final();

}

return _digest;

}



/* Reset the calculate state */

void MD5::reset() {



_finished = false;

/* reset number of bits. */

_count[0] = _count[1] = 0;

/* Load magic initialization constants. */

_state[0] = 0x67452301;

_state[1] = 0xefcdab89;

_state[2] = 0x98badcfe;

_state[3] = 0x10325476;

}



/* Updating the context with a input buffer. */

void MD5::update(const void* input, size_t length) {

update((const byte*)input, length);

}



/* Updating the context with a string. */

void MD5::update(const string& str) {

update((const byte*)str.c_str(), str.length());

}



/* Updating the context with a file. */

void MD5::update(ifstream& in) {



if (!in) {

return;

}



std::streamsize length;

char buffer[BUFFER_SIZE];

while (!in.eof()) {

in.read(buffer, BUFFER_SIZE);

length = in.gcount();

if (length > 0) {

update(buffer, length);

}

}

in.close();

}



/* MD5 block update operation. Continues an MD5 message-digest

operation, processing another message block, and updating the

context.

*/

void MD5::update(const byte* input, size_t length) {



uint32 i, index, partLen;



_finished = false;



/* Compute number of bytes mod 64 */

index = (uint32)((_count[0] >> 3) & 0x3f);



/* update number of bits */

if ((_count[0] += ((uint32)length << 3)) < ((uint32)length << 3)) {

++_count[1];

}

_count[1] += ((uint32)length >> 29);



partLen = 64 - index;



/* transform as many times as possible. */

if (length >= partLen) {



memcpy(&_buffer[index], input, partLen);

transform(_buffer);



for (i = partLen; i + 63 < length; i += 64) {

transform(&input[i]);

}

index = 0;



} else {

i = 0;

}



/* Buffer remaining input */

memcpy(&_buffer[index], &input[i], length - i);

}



/* MD5 finalization. Ends an MD5 message-_digest operation, writing the

the message _digest and zeroizing the context.

*/

void MD5::final() {



byte bits[8];

uint32 oldState[4];

uint32 oldCount[2];

uint32 index, padLen;



/* Save current state and count. */

memcpy(oldState, _state, 16);

memcpy(oldCount, _count, 8);



/* Save number of bits */

encode(_count, bits, 8);



/* Pad out to 56 mod 64. */

index = (uint32)((_count[0] >> 3) & 0x3f);

padLen = (index < 56) ? (56 - index) : (120 - index);

update(PADDING, padLen);



/* Append length (before padding) */

update(bits, 8);



/* Store state in digest */

encode(_state, _digest, 16);



/* Restore current state and count. */

memcpy(_state, oldState, 16);

memcpy(_count, oldCount, 8);

}



/* MD5 basic transformation. Transforms _state based on block. */

void MD5::transform(const byte block[64]) {



uint32 a = _state[0], b = _state[1], c = _state[2], d = _state[3], x[16];



decode(block, x, 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;

}



/* Encodes input (ulong) into output (byte). Assumes length is

a multiple of 4.

*/

void MD5::encode(const uint32* input, byte* output, size_t length) {



for (size_t i = 0, j = 0; j < length; ++i, j += 4) {

output[j]= (byte)(input[i] & 0xff);

output[j + 1] = (byte)((input[i] >> 8) & 0xff);

output[j + 2] = (byte)((input[i] >> 16) & 0xff);

output[j + 3] = (byte)((input[i] >> 24) & 0xff);

}

}



/* Decodes input (byte) into output (ulong). Assumes length is

a multiple of 4.

*/

void MD5::decode(const byte* input, uint32* output, size_t length) {



for (size_t i = 0, j = 0; j < length; ++i, j += 4) {

output[i] = ((uint32)input[j]) | (((uint32)input[j + 1]) << 8) |

(((uint32)input[j + 2]) << 16) | (((uint32)input[j + 3]) << 24);

}

}



/* Convert byte array to hex string. */

string MD5::bytesToHexString(const byte* input, size_t length) {



string str;

str.reserve(length << 1);

for (size_t i = 0; i < length; ++i) {

int t = input[i];

int a = t / 16;

int b = t % 16;

str.append(1, HEX[a]);

str.append(1, HEX);

}

return str;

}



/* Convert digest to string value */

string MD5::toString() {

return bytesToHexString(digest(), 16);

}



string MD5::ToMD5(const string& str) //MD5加密，其中密钥key=xyf，密钥需加在加密之前

{

const string str_word=str+MD5_Key;

reset();

update(str_word);

return toString();

}

那么如何调用呢？

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MD5 md5; //定义MD5的类

md5.update("xxxxxx");//因为update函数只接收string类型，所以使用getbuffer()函数转换CString为string

char*p = md5.toString().c_str();

不过值得注意的是你如果还要计算另一个字符串的md5值，那么你得调用md5.reset()方法重置