散列加密--MD5原理

原創 工农村贴膜小哥 2020-05-31 20:47

介紹

MD5是一種散列算法，它輸入任意長度的原文，通過一個散列算法，會得到固定長度128位（16字節）的散列值。由於修改原文一點數據，獲得的散列值完全不同，常常用在放置數據篡改，數字簽名，以及如linux登錄密碼存儲的安全認證中

原理

typedef struct
{
	unsigned long relute[4];//輸出的16字節,初始狀態爲4個幻數
	unsigned char block[64];//一個分組
	unsigned long state;//狀態
	unsigned long long length;//數據長度
} MD5_CONT;

step 1

MD5 以512位（64字節）分組來處理數據,將64字節數據送到控制器緩衝區中

	while (length-64>=0)
	{
		memcpy(md5_con.block,data+(i++<<6),64);
		block_trans(&md5_con);
		length -= 64;
	}

step 2 散列算法運算

#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
#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) + (unsigned int)(ac);(a) = ROTATE_LEFT ((a), (s));(a) += (b);}
#define GG(a, b, c, d, x, s, ac)  {(a) += G((b), (c), (d)) + (x) + (unsigned int)(ac);(a) = ROTATE_LEFT ((a), (s));(a) += (b);}
#define HH(a, b, c, d, x, s, ac)  {(a) += H((b), (c), (d)) + (x) + (unsigned int)(ac);(a) = ROTATE_LEFT ((a), (s));(a) += (b);}
#define II(a, b, c, d, x, s, ac)  {(a) += I((b), (c), (d)) + (x) + (unsigned int)(ac);(a) = ROTATE_LEFT ((a), (s));(a) += (b); }

block_trans()進行每個分組算法運算，通過循環函數運算，得到新的a,b,c,d。a,b,c,d的初始值是4個標準的幻數0x01234567,0x89abcdef…使用時如下賦值，因爲內存存儲時候是低位存低位.
FF(a, b, c, d, x[0], S11, 0xd76aa478)，a,b,c,d是待輸出的128位數據，x[0]表示該分組的第一個子分組（分組分爲16子分組參與運算），S11代表移位的位數，0xd76aa478，w爲一個自然數，每次運算都不相同。

	con->relute[0] = 0x67452301;
	con->relute[1] = 0xefcdab89;
	con->relute[2] = 0x98badcfe;
	con->relute[3] = 0x10325476;

void block_trans(MD5_CONT *con)
{
  unsigned	int a = con->relute[0], b = con->relute[1], c = con->relute[2], d = con->relute[3], x[16];
    Decode(x, con->block, 64);//子分組
	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 */
	con->relute[0] += a;
	con->relute[1] += b;
	con->relute[2] += c;
	con->relute[3] += d;
}

step 3 填充

step 2一直循環，直到數據長度小於64字節，也就是最後一個分組。最後一個分組則進行填充
將分組的任意長度數據填充到448位（56字節）。（如果剛好56字節，則填充一輪，64個字節）

填充的結構：第一個爲0x80後面填充0。

void block_padding(MD5_CONT *con, long len)//剩餘的長度
{
	int pad_len=0;//需要補全的長度
	char tran_len[8] = {0};
	int pad[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
		};
	pad_len = (len < 56) ? (56 - len) : (120 - len);
	if (len >=56)//填充後不爲最後一個分組
	{
		memcpy(con->block + len, pad, len);//補全到448位,56字節
		block_trans(&con);
		memcpy(con->block , pad+len, pad_len-len);
	}
	else//填充後爲最後一個分組
	memcpy(con->block+len,pad,pad_len);//補全到448位,56字節
	Encode(tran_len, &con->length, 8);



}

step 4 填充長度

在經過step3 後最後一個分組爲56字節，還需要填充8字節的數據長度，構成64字節，最後輸出4個運算後的128位散列值。

	memcpy(con->block+56,tran_len,8);//補全556位
	block_trans(&con);

源碼

#pragma once
#include <stdio.h> 
#include <time.h> 
#include <string.h>
#include<stdlib.h>

#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
#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) + (unsigned int)(ac);(a) = ROTATE_LEFT ((a), (s));(a) += (b);}
#define GG(a, b, c, d, x, s, ac)  {(a) += G((b), (c), (d)) + (x) + (unsigned int)(ac);(a) = ROTATE_LEFT ((a), (s));(a) += (b);}
#define HH(a, b, c, d, x, s, ac)  {(a) += H((b), (c), (d)) + (x) + (unsigned int)(ac);(a) = ROTATE_LEFT ((a), (s));(a) += (b);}
#define II(a, b, c, d, x, s, ac)  {(a) += I((b), (c), (d)) + (x) + (unsigned int)(ac);(a) = ROTATE_LEFT ((a), (s));(a) += (b); }

typedef struct
{
	unsigned long relute[4];//輸出的16字節
	unsigned char block[64];///一個分組
	unsigned long state;
	unsigned long long length;
} MD5_CONT;

int MD5_Init(MD5_CONT *);
int MD5_EN(char * ,int,char *);
int MD5_EN_File(char *);


#include"test.h"
void Encode(unsigned char *output, unsigned int *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);
	}
}
//將512位的分組轉換爲16個子分組
void Decode(unsigned int *output, unsigned char *input, unsigned int len)
{
	unsigned int i, j;

	for (i = 0, j = 0; j < len; i++, j += 4)
	{
		output[i] = ((unsigned int)input[j]) | (((unsigned int)input[j + 1]) << 8) |
			(((unsigned int)input[j + 2]) << 16) | (((unsigned int)input[j + 3]) << 24);
	}
}
void block_trans(MD5_CONT *con)
{
  unsigned	int a = con->relute[0], b = con->relute[1], c = con->relute[2], d = con->relute[3], x[16];
    Decode(x, con->block, 64);//子分組
	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 */
	con->relute[0] += a;
	con->relute[1] += b;
	con->relute[2] += c;
	con->relute[3] += d;
}

void block_padding(MD5_CONT *con, long len)//剩餘的長度
{
	int pad_len=0;//需要補全的長度
	char tran_len[8] = {0};
	int pad[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
		};
	pad_len = (len < 56) ? (56 - len) : (120 - len);
	if (len >=56)
	{
		memcpy(con->block + len, pad, len);//補全到448位,56字節
		block_trans(&con);
		memcpy(con->block , pad+len, pad_len-len);
	}
	else
	memcpy(con->block+len,pad,pad_len);//補全到448位,56字節
	Encode(tran_len, &con->length, 8);
	memcpy(con->block+56,tran_len,8);//補全556位
	block_trans(&con);
}

int MD5_Init(MD5_CONT *con,long len)
{
	con->relute[0] = 0x67452301;
	con->relute[1] = 0xefcdab89;
	con->relute[2] = 0x98badcfe;
	con->relute[3] = 0x10325476;
	con->length = len;
	con->state = 1;
}


int MD5_EN(char *data, int length,char *tr_data)
{
	MD5_CONT md5_con;
	int i = 0;
	MD5_Init(&md5_con,length);

	while (length-64>=0)
	{
		memcpy(md5_con.block,data+(i++<<6),64);
		block_trans(&md5_con);
		length -= 64;
	}

	memcpy(md5_con.block, data + (i<< 6), length);//將需要補全的數據拷貝
	block_padding(&md5_con,length);

	Encode(tr_data, md5_con.relute, 16);

}
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