MD5消息摘要算法

                          1 #include<iostream>
  2 #include<string>
  3usingnamespace std;
  4#define shift(x, n) (((x) << (n)) | ((x) >> (32-(n))))//右移的时候，高位一定要补零，而不是补充符号位  5#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))    
  6#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
  7#define H(x, y, z) ((x) ^ (y) ^ (z))
  8#define I(x, y, z) ((y) ^ ((x) | (~z)))
  9#define A 0x67452301
 10#define B 0xefcdab89
 11#define C 0x98badcfe
 12#define D 0x10325476
 13//strBaye的长度 14 unsigned int strlength;
 15//A,B,C,D的临时变量 16 unsigned int atemp;
 17 unsigned int btemp;
 18 unsigned int ctemp;
 19 unsigned int dtemp;
 20//常量ti unsigned int(abs(sin(i+1))*(2pow32)) 21const unsigned int k[]={
 220xd76aa478,0xe8c7b756,0x242070db,0xc1bdceee,
 230xf57c0faf,0x4787c62a,0xa8304613,0xfd469501,0x698098d8,
 240x8b44f7af,0xffff5bb1,0x895cd7be,0x6b901122,0xfd987193,
 250xa679438e,0x49b40821,0xf61e2562,0xc040b340,0x265e5a51,
 260xe9b6c7aa,0xd62f105d,0x02441453,0xd8a1e681,0xe7d3fbc8,
 270x21e1cde6,0xc33707d6,0xf4d50d87,0x455a14ed,0xa9e3e905,
 280xfcefa3f8,0x676f02d9,0x8d2a4c8a,0xfffa3942,0x8771f681,
 290x6d9d6122,0xfde5380c,0xa4beea44,0x4bdecfa9,0xf6bb4b60,
 300xbebfbc70,0x289b7ec6,0xeaa127fa,0xd4ef3085,0x04881d05,
 310xd9d4d039,0xe6db99e5,0x1fa27cf8,0xc4ac5665,0xf4292244,
 320x432aff97,0xab9423a7,0xfc93a039,0x655b59c3,0x8f0ccc92,
 330xffeff47d,0x85845dd1,0x6fa87e4f,0xfe2ce6e0,0xa3014314,
 340x4e0811a1,0xf7537e82,0xbd3af235,0x2ad7d2bb,0xeb86d391};
 35//向左位移数 36const unsigned int s[]={7,12,17,22,7,12,17,22,7,12,17,22,7,
 3712,17,22,5,9,14,20,5,9,14,20,5,9,14,20,5,9,14,20,
 384,11,16,23,4,11,16,23,4,11,16,23,4,11,16,23,6,10,
 3915,21,6,10,15,21,6,10,15,21,6,10,15,21};
 40constchar str16[]="0123456789abcdef";
 41void mainLoop(unsigned int M[])
 42{
 43     unsigned int f,g;
 44     unsigned int a=atemp;
 45     unsigned int b=btemp;
 46     unsigned int c=ctemp;
 47     unsigned int d=dtemp;
 48for (unsigned int i = 0; i < 64; i++)
 49    {
 50if(i<16){
 51             f=F(b,c,d);
 52             g=i;
 53         }elseif (i<32)
 54        {
 55             f=G(b,c,d);
 56             g=(5*i+1)%16;
 57         }elseif(i<48){
 58             f=H(b,c,d);
 59             g=(3*i+5)%16;
 60         }else{
 61             f=I(b,c,d);
 62             g=(7*i)%16;
 63        }
 64         unsigned int tmp=d;
 65         d=c;
 66         c=b;
 67         b=b+shift((a+f+k[i]+M[g]),s[i]);
 68         a=tmp;
 69    }
 70     atemp=a+atemp;
 71     btemp=b+btemp;
 72     ctemp=c+ctemp;
 73     dtemp=d+dtemp;
 74}
 75/* 76*填充函数
 77*处理后应满足bits≡448(mod512),字节就是bytes≡56（mode64)
 78*填充方式为先加一个1,其它位补零
 79*最后加上64位的原来长度
 80*/ 81 unsigned int* add(string str)
 82{
 83     unsigned int num=((str.length()+8)/64)+1;//以512位,64个字节为一组 84     unsigned int *strByte=new unsigned int[num*16];    //64/4=16,所以有16个整数 85     strlength=num*16;
 86for (unsigned int i = 0; i < num*16; i++)
 87         strByte[i]=0;
 88for ( i=0; i <str.length(); i++)
 89    {
 90         strByte[i>>2]|=(str[i])<<((i%4)*8);//一个整数存储四个字节，i>>2表示i/4 一个unsigned int对应4个字节，保存4个字符信息 91    }
 92     strByte[str.length()>>2]|=0x80<<(((str.length()%4))*8);//尾部添加1 一个unsigned int保存4个字符信息,所以用128左移 93/* 94    *添加原长度，长度指位的长度，所以要乘8，然后是小端序，所以放在倒数第二个,这里长度只用了32位
 95*/ 96     strByte[num*16-2]=str.length()*8;
 97return strByte;
 98}
 99string changeHex(int a)
100{
101int b;
102string str1;
103string str="";
104for(int i=0;i<4;i++)
105    {
106         str1="";
107         b=((a>>i*8)%(1<<8))&0xff;   //逆序处理每个字节108for (int j = 0; j < 2; j++)
109        {
110             str1.insert(0,1,str16[b%16]);
111             b=b/16;
112        }
113         str+=str1;
114    }
115return str;
116}
117string getMD5(string source)
118{
119     atemp=A;    //初始化120     btemp=B;
121     ctemp=C;
122     dtemp=D;
123     unsigned int *strByte=add(source);
124for(unsigned int i=0;i<strlength/16;i++)
125    {
126         unsigned int num[16];
127for(unsigned int j=0;j<16;j++)
128             num[j]=strByte[i*16+j];
129        mainLoop(num);
130    }
131return changeHex(atemp).append(changeHex(btemp)).append(changeHex(ctemp)).append(changeHex(dtemp));
132}
133 unsigned int main()
134{
135string ss;
136//    cin>>ss;137string s=getMD5("abc");
138     cout<<s;
139return0;
140 }