md5.cpp

vc环境下的MD5信息摘要算法的实现

#include "md5.h"
using namespace std;

#define S11 7//向左循环位移位数
#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
#define F(x,y,z) ((x&y)|((~x)&z))//^:XOR,&:AND,|:OR,~:NOT
#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))))//ROTATE_LEFT rotates x left n bits.

/* 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'
};

MD5::MD5() {// Default construct
	reset();
}

MD5::MD5(const string &str) {// Construct a MD5 object with a string
	reset();
	update(str);
}

const byte* MD5::digest() {// Return the message-digest
	if (!_finished) {
		_finished = true;
		final();
	}
	return _digest;
}

void MD5::reset() {//Reset the calculate state
	_finished = false;
	/* reset number of bits. */
	_count[0] = _count[1] = 0;

	_state[0] = 0x67452301;//a,b,c,d初始值
	_state[1] = 0xefcdab89;
	_state[2] = 0x98badcfe;
	_state[3] = 0x10325476;
}

void MD5::update(const string &str) {//Updating the context with a string
	update((const byte*)str.c_str(), str.length());
}

/* 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) {

	ulong i, index, partLen;

	_finished = false;

	/* Compute number of bytes mod 64 */
	index = (ulong)((_count[0] >> 3) & 0x3f);

	/* update number of bits */
	if((_count[0] += ((ulong)length << 3)) < ((ulong)length << 3))
		_count[1]++;
	_count[1] += ((ulong)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];
	ulong oldState[4];
	ulong oldCount[2];
	ulong 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 = (ulong)((_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);
}

void MD5::transform(const byte block[64]) {//压缩函数:H
	ulong a=_state[0],b=_state[1],c=_state[2],d=_state[3],x[16];//中间变量

	decode(block, x, 64);

	FF (a, b, c, d, x[ 0], S11, 0xd76aa478); //第一轮
	FF (d, a, b, c, x[ 1], S12, 0xe8c7b756); 
	FF (c, d, a, b, x[ 2], S13, 0x242070db); 
	FF (b, c, d, a, x[ 3], S14, 0xc1bdceee); 
	FF (a, b, c, d, x[ 4], S11, 0xf57c0faf); 
	FF (d, a, b, c, x[ 5], S12, 0x4787c62a); 
	FF (c, d, a, b, x[ 6], S13, 0xa8304613); 
	FF (b, c, d, a, x[ 7], S14, 0xfd469501); 
	FF (a, b, c, d, x[ 8], S11, 0x698098d8); 
	FF (d, a, b, c, x[ 9], S12, 0x8b44f7af); 
	FF (c, d, a, b, x[10], S13, 0xffff5bb1); 
	FF (b, c, d, a, x[11], S14, 0x895cd7be); 
	FF (a, b, c, d, x[12], S11, 0x6b901122); 
	FF (d, a, b, c, x[13], S12, 0xfd987193); 
	FF (c, d, a, b, x[14], S13, 0xa679438e); 
	FF (b, c, d, a, x[15], S14, 0x49b40821); 

	GG (a, b, c, d, x[ 1], S21, 0xf61e2562); //第二轮
	GG (d, a, b, c, x[ 6], S22, 0xc040b340); 
	GG (c, d, a, b, x[11], S23, 0x265e5a51); 
	GG (b, c, d, a, x[ 0], S24, 0xe9b6c7aa); 
	GG (a, b, c, d, x[ 5], S21, 0xd62f105d); 
	GG (d, a, b, c, x[10], S22,  0x2441453); 
	GG (c, d, a, b, x[15], S23, 0xd8a1e681); 
	GG (b, c, d, a, x[ 4], S24, 0xe7d3fbc8); 
	GG (a, b, c, d, x[ 9], S21, 0x21e1cde6); 
	GG (d, a, b, c, x[14], S22, 0xc33707d6); 
	GG (c, d, a, b, x[ 3], S23, 0xf4d50d87); 
	GG (b, c, d, a, x[ 8], S24, 0x455a14ed); 
	GG (a, b, c, d, x[13], S21, 0xa9e3e905); 
	GG (d, a, b, c, x[ 2], S22, 0xfcefa3f8); 
	GG (c, d, a, b, x[ 7], S23, 0x676f02d9); 
	GG (b, c, d, a, x[12], S24, 0x8d2a4c8a); 

	HH (a, b, c, d, x[ 5], S31, 0xfffa3942); //第三轮
	HH (d, a, b, c, x[ 8], S32, 0x8771f681);
	HH (c, d, a, b, x[11], S33, 0x6d9d6122); 
	HH (b, c, d, a, x[14], S34, 0xfde5380c); 
	HH (a, b, c, d, x[ 1], S31, 0xa4beea44); 
	HH (d, a, b, c, x[ 4], S32, 0x4bdecfa9); 
	HH (c, d, a, b, x[ 7], S33, 0xf6bb4b60); 
	HH (b, c, d, a, x[10], S34, 0xbebfbc70); 
	HH (a, b, c, d, x[13], S31, 0x289b7ec6); 
	HH (d, a, b, c, x[ 0], S32, 0xeaa127fa); 
	HH (c, d, a, b, x[ 3], S33, 0xd4ef3085); 
	HH (b, c, d, a, x[ 6], S34,  0x4881d05); 
	HH (a, b, c, d, x[ 9], S31, 0xd9d4d039); 
	HH (d, a, b, c, x[12], S32, 0xe6db99e5); 
	HH (c, d, a, b, x[15], S33, 0x1fa27cf8); 
	HH (b, c, d, a, x[ 2], S34, 0xc4ac5665); 

	II (a, b, c, d, x[ 0], S41, 0xf4292244); //第四轮
	II (d, a, b, c, x[ 7], S42, 0x432aff97); 
	II (c, d, a, b, x[14], S43, 0xab9423a7); 
	II (b, c, d, a, x[ 5], S44, 0xfc93a039); 
	II (a, b, c, d, x[12], S41, 0x655b59c3); 
	II (d, a, b, c, x[ 3], S42, 0x8f0ccc92); 
	II (c, d, a, b, x[10], S43, 0xffeff47d); 
	II (b, c, d, a, x[ 1], S44, 0x85845dd1); 
	II (a, b, c, d, x[ 8], S41, 0x6fa87e4f); 
	II (d, a, b, c, x[15], S42, 0xfe2ce6e0); 
	II (c, d, a, b, x[ 6], S43, 0xa3014314); 
	II (b, c, d, a, x[13], S44, 0x4e0811a1);
	II (a, b, c, d, x[ 4], S41, 0xf7537e82); 
	II (d, a, b, c, x[11], S42, 0xbd3af235); 
	II (c, d, a, b, x[ 2], S43, 0x2ad7d2bb); 
	II (b, c, d, a, x[ 9], S44, 0xeb86d391); 

	_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 ulong *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, ulong *output, size_t length) {

	for(size_t i=0, j=0; j<length; i++, j+=4) {	
		output[i] = ((ulong)input[j]) | (((ulong)input[j+1]) << 8) |
			(((ulong)input[j+2]) << 16) | (((ulong)input[j+3]) << 24);
	}
}


string MD5::bytesToHexString(const byte *input, size_t length) {//转化成16进制
	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[b]);
	}
	return str;
}

string MD5::toString() {//输出结果
	return bytesToHexString(digest(), 16);
}