MD5加密算法原理及实现

 1 #ifndef MD5H
 2 #define MD5H
 3 #include <math.h>
 4 #include <Windows.h>
 5 
 6 void ROL(unsigned int &s, unsigned short cx); //32位数循环左移实现函数
 7 void ltob(unsigned int &i); //B\L互转，接受UINT类型
 8 unsigned int* MD5(const char* mStr); //接口函数，并执行数据填充，计算MD5时调用此函数
 9 
10 #endif

  1 #include "MD5.h"
  2 
  3 /*4组计算函数*/
  4 inline unsigned int F(unsigned int X, unsigned int Y, unsigned int Z)
  5 {
  6     return (X & Y) | ((~X) & Z);
  7 }
  8 inline unsigned int G(unsigned int X, unsigned int Y, unsigned int Z)
  9 {
 10     return (X & Z) | (Y & (~Z));
 11 }
 12 inline unsigned int H(unsigned int X, unsigned int Y, unsigned int Z)
 13 {
 14     return X ^ Y ^ Z;
 15 }
 16 inline unsigned int I(unsigned int X, unsigned int Y, unsigned int Z)
 17 {
 18     return Y ^ (X | (~Z));
 19 }
 20 /*4组计算函数结束*/
 21 
 22 /*32位数循环左移实现函数*/
 23 void ROL(unsigned int &s, unsigned short cx)
 24 {
 25     if (cx > 32)cx %= 32;
 26     s = (s << cx) | (s >> (32 - cx));
 27     return;
 28 }
 29 
 30 /*B\L互转，接收UINT类型*/
 31 void ltob(unsigned int &i)
 32 {
 33     unsigned int tmp = i;//保存副本
 34     byte *psour = (byte*)&tmp, *pdes = (byte*)&i;
 35     pdes += 3;//调整指针，准备左右调转
 36     for (short i = 3; i >= 0; --i)
 37     {
 38         CopyMemory(pdes - i, psour + i, 1);
 39     }
 40     return;
 41 }
 42 
 43 /*
 44 MD5循环计算函数，label=第几轮循环（1<=label<=4），lGroup数组=4个种子副本，M=数据（16组32位数指针）
 45 种子数组排列方式: --A--D--C--B--，即 lGroup[0]=A; lGroup[1]=D; lGroup[2]=C; lGroup[3]=B;
 46 */
 47 void AccLoop(unsigned short label, unsigned int *lGroup, void *M)
 48 {
 49     unsigned int *i1, *i2, *i3, *i4, TAcc, tmpi = 0; //定义:4个指针； T表累加器； 局部变量
 50     typedef unsigned int(*clac)(unsigned int X, unsigned int Y, unsigned int Z); //定义函数类型
 51     const unsigned int rolarray[4][4] = {
 52         { 7, 12, 17, 22 },
 53         { 5, 9, 14, 20 },
 54         { 4, 11, 16, 23 },
 55         { 6, 10, 15, 21 }
 56     };//循环左移-位数表
 57     const unsigned short mN[4][16] = {
 58         { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 },
 59         { 1, 6, 11, 0, 5, 10, 15, 4, 9, 14, 3, 8, 13, 2, 7, 12 },
 60         { 5, 8, 11, 14, 1, 4, 7, 10, 13, 0, 3, 6, 9, 12, 15, 2 },
 61         { 0, 7, 14, 5, 12, 3, 10, 1, 8, 15, 6, 13, 4, 11, 2, 9 }
 62     };//数据坐标表
 63     const unsigned int *pM = static_cast<unsigned int*>(M);//转换类型为32位的Uint
 64     TAcc = ((label - 1) * 16) + 1; //根据第几轮循环初始化T表累加器
 65     clac clacArr[4] = { F, G, H, I }; //定义并初始化计算函数指针数组
 66 
 67     /*一轮循环开始（16组->16次）*/
 68     for (short i = 0; i < 16; ++i)
 69     {
 70         /*进行指针自变换*/
 71         i1 = lGroup + ((0 + i) % 4);
 72         i2 = lGroup + ((3 + i) % 4);
 73         i3 = lGroup + ((2 + i) % 4);
 74         i4 = lGroup + ((1 + i) % 4);
 75 
 76         /*第一步计算开始: A+F(B,C,D)+M[i]+T[i+1] 注:第一步中直接计算T表*/
 77         tmpi = (*i1 + clacArr[label - 1](*i2, *i3, *i4) + pM[(mN[label - 1][i])] + (unsigned int)(0x100000000UL * abs(sin((double)(TAcc + i)))));
 78         ROL(tmpi, rolarray[label - 1][i % 4]);//第二步:循环左移
 79         *i1 = *i2 + tmpi;//第三步:相加并赋值到种子
 80     }
 81     return;
 82 }
 83 
 84 /*接口函数，并执行数据填充*/
 85 unsigned int* MD5(const char* mStr)
 86 {
 87     unsigned int mLen = strlen(mStr); //计算字符串长度
 88     if (mLen < 0) return 0;
 89     unsigned int FillSize = 448 - ((mLen * 8) % 512); //计算需填充的bit数
 90     unsigned int FSbyte = FillSize / 8; //以字节表示的填充数
 91     unsigned int BuffLen = mLen + 8 + FSbyte; //缓冲区长度或者说填充后的长度
 92     unsigned char *md5Buff = new unsigned char[BuffLen]; //分配缓冲区
 93     CopyMemory(md5Buff, mStr, mLen); //复制字符串到缓冲区
 94 
 95     /*数据填充开始*/
 96     md5Buff[mLen] = 0x80; //第一个bit填充1
 97     ZeroMemory(&md5Buff[mLen + 1], FSbyte - 1); //其它bit填充0，另一可用函数为FillMemory
 98     unsigned long long lenBit = mLen * 8ULL; //计算字符串长度，准备填充
 99     CopyMemory(&md5Buff[mLen + FSbyte], &lenBit, 8); //填充长度
100     /*数据填充结束*/
101 
102     /*运算开始*/
103     unsigned int LoopNumber = BuffLen / 64; //以16个字节为一分组，计算分组数量
104     unsigned int A = 0x67452301, B = 0x0EFCDAB89, C = 0x98BADCFE, D = 0x10325476;//初始4个种子，小端类型
105     unsigned int *lGroup = new unsigned int[4]{ A, D, C, B}; //种子副本数组,并作为返回值返回
106     for (unsigned int Bcount = 0; Bcount < LoopNumber; ++Bcount) //分组大循环开始
107     {
108         /*进入4次计算的小循环*/
109         for (unsigned short Lcount = 0; Lcount < 4;)
110         {
111             AccLoop(++Lcount, lGroup, &md5Buff[Bcount * 16]);
112         }
113         /*数据相加作为下一轮的种子或者最终输出*/
114         A = (lGroup[0] += A);
115         B = (lGroup[3] += B);
116         C = (lGroup[2] += C);
117         D = (lGroup[1] += D);
118     }
119     /*由于内存中的为大端字节，转成小端才能正常显示*/
120     ltob(lGroup[0]);
121     ltob(lGroup[1]);
122     ltob(lGroup[2]);
123     ltob(lGroup[3]);
124     delete[] md5Buff; //清除内存并返回
125     return lGroup;
126 }

 1 #include <iostream>
 2 #include <string.h>
 3 #include <stdlib.h>
 4 #include "MD5.h"
 5 
 6 int main(int argc, char **argv)
 7 {
 8     char tmpstr[256], buf[4][10];
 9     std::cout << "请输入要加密的字符串：";
10     std::cin >> tmpstr;
11     unsigned int* tmpGroup = MD5(tmpstr);
12     sprintf_s(buf[0], "%8X", tmpGroup[0]);
13     sprintf_s(buf[1], "%8X", tmpGroup[3]);
14     sprintf_s(buf[2], "%8X", tmpGroup[2]);
15     sprintf_s(buf[3], "%8X", tmpGroup[1]);
16     std::cout <<"MD5:"<< buf[0] << buf[1] << buf[2] << buf[3] << std::endl;
17     
18     delete[] tmpGroup;
19     return 0; //在此下断点才能看到输出的值
20 }