MD5加密算法（c语言实现）

      这次我分享的是MD5加密算法。其实MD5这个大名在还没上密码学课之前我就听说过了，那时我才刚学php，视频里面的讲师说像密码这种重要的信息要用md5（）函数处理下再存数据库，这么一说起来其实MD5算是我接触的第一个现代密码呢

     考虑到可能有些人是为了科普一下才点进来看的，我还是结合自身经验和课本知识把MD5加密原理讲一下把，MD5算法的具体过程有以下4步：

    （1）附加填充位 

      课本原话：填充一个‘1’和若干个‘0’使其长度模512与448同余，然后再将消息的真实长度以64bit表示附加在填充结果后面，从而使得消息长度恰好为512bit的整数倍。（不知道这段话你们看懂没有，方正我看了很久才看懂的，大概以前语文真的是体育老师教的）

      举例说明吧：

      如明文为iscbupt

      其16ascII码是105，115，99，98，117，112，116，转换成二进制便是01101001 01110011 01100011 01100010 01110101 01110000 01110100，这是长度为56，要使其长度模512与448同余，则需补充一个‘1’和391个‘0’。因为消息长度为56，所以用64位二进制表示为00110000   00~00（56个‘0’）。到目前为止512位全部填充完整了~

    （2)初始化链接变量 

      课本原话：MD5中有A、B、C、D 4个32为寄存器，最开始存放4个固定的32位的整数参数，即初始链接变量，这些参数用于第1轮运算。

      A=0x12345678，B=0x89ABCDEF，C=0xFEDCBA98，D=0x76543210

   （3）分组处理（迭代压缩）  

     课本原话：MD5算法的分组处理（压缩函数）与分组密码的分组处理相似。它由4轮组成，512bit的消息分组Mi被分成16个子分组（每个子分组为32bit）参与每轮16步函数运算，即每轮包括16个步骤。每步的输入是4个32bit的链接变量（插句话~也就是A、B、C、D）和一个32bit的消息分组（是Mi哦~~），输出为32位值。经过4轮共64步后，得到的4个寄存器值分别与输入链接变量（也就是初始的A、B、C、D）进行模加，即是当前消息的中间散列值。

     明文是iscbupt的Mi如下：

     M0:01101001 01110011 01100011 01100010

     M1:01110101 01110000 01110100 10000000

     M2:00000000 00000000 00000000 00000000

     ................

     M14:00111000 00000000 00000000 00000000

     M15:00000000 00000000 00000000 00000000

   （4）步函数

     由于课本的图无法上传，那这里就由我来说下啦~~

     所有大轮（上文所说的4轮）里的所有小轮（16轮）都是同一个步函数A=B+((A+f(B,C,D)+M[j]+T[i])= 10) { switch (add) { case 10:printf("a"); break; case 11:printf("b"); break; case 12:printf("c"); break; case 13:printf("d"); break; case 14:printf("e"); break; case 15:printf("f"); break; } } else printf("%d", add); } } /* 与函数 */ void yu(int *a, int *b,int *temp) { int i; for (i = 0; i < 32; i++) //同为1为1，否则为0 { if (a[i] == 1 && b[i] == 1) temp[i] = 1; else temp[i] = 0; } } /* 或函数 */ void huo(int *a, int *b, int *temp) { int i; for (i = 0; i < 32; i++) //同0为0，否则为1 { if (a[i] == 0 && b[i] == 0) temp[i] = 0; else temp[i] = 1; } } /* 非函数 */ void fei(int *a, int *temp) { int i; for (i = 0; i < 32; i++) { if (a[i] == 0) temp[i] = 1; else temp[i] = 0; } } /*异或函数*/ void yihuo(int *a, int *b, int *temp) { int i; for (i = 0; i < 32; i++) //相同为0，不同为1 { if (a[i] != b[i]) temp[i] = 1; else temp[i] = 0; } } /* 模二的32次加 */ void jia(int *a, int *b, int *temp) { int i,jin; jin = 0; for (i = 0; i < 32; i++) { if (a[31 - i] + b[31 - i] + jin>1) { temp[31 - i] = a[31 - i] + b[31 - i] + jin - 2; jin = 1; } else { temp[31 - i] = a[31 - i] + b[31 - i]+jin; jin = 0; } } } /* F函数 */ void F(int *b, int *c, int *d,int *temp1,int *temp2) { /* F(x,y,z)=(x∧y)∨(¬x∧z) */ yu(b, c, temp1); fei(b, temp2); yu(temp2, d, temp2); huo(temp1, temp2, temp2); } /* G函数 */ void G(int *b, int *c, int *d, int *temp1, int *temp2) { /* G(x,y,z)=(x∧z)∨(y∧¬z) */ yu(b, d, temp1); fei(d, temp2); yu(temp2, c, temp2); huo(temp1, temp2, temp2); } /* H函数 */ void H(int *b, int *c, int *d, int *temp) { /* H(x,y,z)=x⊕y⊕z */ yihuo(b, c, temp); yihuo(temp, d, temp); } /* I函数 */ void I(int *b, int *c, int *d, int *temp) { /* I(x,y,z)=y⊕(x∨¬z) */ fei(d, temp); huo(b, temp, temp); yihuo(c, temp, temp); } /*左移函数*/ void move(int step, int *temp1, int *temp2) { int i; for (i = 0; i < 32 - step; i++) temp2[i] = temp1[i + step]; for (i = 0; i < step; i++) temp2[32 - step + i] = temp1[i]; } /*每一大轮的16小轮循环函数*/ void round(int *a, int *b, int *c, int *d, int *m, int *md5, int r, char *t1, char *t2, char *t3, char *t4, char *t5, char *t6, char *t7, char *t8, char *t9, char *t10, char *t11, char *t12, char *t13, char *t14, char *t15, char *t16 ) { int i, j, in, step , temp1[32], temp2[32]; for (i = 0; i < 16; i++) { switch (r) //根据r判断所选的逻辑函数 { case 1:F(b, c, d, temp1, temp2); break; case 2:G(b, c, d, temp1, temp2); break; case 3:H(b, c, d, temp2); break; case 4:I(b, c, d, temp2); break; } in = m[i]; for (j = 0; j < 32; j++) temp1[j] = md5[in * 32 + j]; jia(temp2, temp1, temp2); switch (i + 1) //选择t[] { case 1:shiliuzhuaner(t1, temp1); break; case 2:shiliuzhuaner(t2, temp1); break; case 3:shiliuzhuaner(t3, temp1); break; case 4:shiliuzhuaner(t4, temp1); break; case 5:shiliuzhuaner(t5, temp1); break; case 6:shiliuzhuaner(t6, temp1); break; case 7:shiliuzhuaner(t7, temp1); break; case 8:shiliuzhuaner(t8, temp1); break; case 9:shiliuzhuaner(t9, temp1); break; case 10:shiliuzhuaner(t10, temp1); break; case 11:shiliuzhuaner(t11, temp1); break; case 12:shiliuzhuaner(t12, temp1); break; case 13:shiliuzhuaner(t13, temp1); break; case 14:shiliuzhuaner(t14, temp1); break; case 15:shiliuzhuaner(t15, temp1); break; case 16:shiliuzhuaner(t16, temp1); break; } jia(temp2, temp1, temp2); jia(temp2, a, temp2); switch(r) //根据r为左移步数step赋值 { case 1:switch (i % 4 + 1){ case 1:step = 7; break; case 2:step = 12; break; case 3:step = 17; break; case 4:step = 22; break; }break; case 2:switch (i % 4 + 1){ case 1:step = 5; break; case 2:step = 9; break; case 3:step = 14; break; case 4:step = 20; break; }break; case 3:switch (i % 4 + 1){ case 1:step = 4; break; case 2:step = 11; break; case 3:step = 16; break; case 4:step = 23; break; }break; case 4:switch (i % 4 + 1){ case 1:step = 6; break; case 2:step = 10; break; case 3:step = 15; break; case 4:step = 21; break; }break; } move(step, temp2, temp1); jia(temp1, b, temp2); for (j = 0; j < 32; j++) { a[j] = d[j]; d[j] = c[j]; c[j] = b[j]; b[j] = temp2[j]; } /*若想输出每轮a、b、c、d的值，把下面的注释取消即可*/ /*printf("第%d大轮的第%d小轮\n", r, i); abcd_out(a); printf(" "); abcd_out(b); printf(" "); abcd_out(c); printf(" "); abcd_out(d); printf("\n");*/ } } /* 主函数 */ int main() { char ch, /* 一大坨t[] */ t1[8] = { 'd', '7', '6', 'a', 'a', '4', '7', '8' }, t2[8] = { 'e', '8', 'c', '7', 'b', '7', '5', '6' }, t3[8] = { '2', '4', '2', '0', '7', '0', 'd', 'b' }, t4[8] = { 'c', '1', 'b', 'd', 'c', 'e', 'e', 'e' }, t5[8] = { 'f', '5', '7', 'c', '0', 'f', 'a', 'f' }, t6[8] = { '4', '7', '8', '7', 'c', '6', '2', 'a' }, t7[8] = { 'a', '8', '3', '0', '4', '6', '1', '3' }, t8[8] = { 'f', 'd', '4', '6', '9', '5', '0', '1' }, t9[8] = { '6', '9', '8', '0', '9', '8', 'd', '8' }, t10[8] = { '8', 'b', '4', '4', 'f', '7', 'a', 'f' }, t11[8] = { 'f', 'f', 'f', 'f', '5', 'b', 'b', '1' }, t12[8] = { '8', '9', '5', 'c', 'd', '7', 'b', 'e' }, t13[8] = { '6', 'b', '9', '0', '1', '1', '2', '2' }, t14[8] = { 'f', 'd', '9', '8', '7', '1', '9', '3' }, t15[8] = { 'a', '6', '7', '9', '4', '3', '8', 'e' }, t16[8] = { '4', '9', 'b', '4', '0', '8', '2', '1' }, t17[8] = { 'f', '6', '1', 'e', '2', '5', '6', '2' }, t18[8] = { 'c', '0', '4', '0', 'b', '3', '4', '0' }, t19[8] = { '2', '6', '5', 'e', '5', 'a', '5', '1' }, t20[8] = { 'e', '9', 'b', '6', 'c', '7', 'a', 'a' }, t21[8] = { 'd', '6', '2', 'f', '1', '0', '5', 'd' }, t22[8] = { '0', '2', '4', '4', '1', '4', '5', '3' }, t23[8] = { 'd', '8', 'a', '1', 'e', '6', '8', '1' }, t24[8] = { 'e', '7', 'd', '3', 'f', 'b', 'c', '8' }, t25[8] = { '2', '1', 'e', '1', 'c', 'd', 'e', '6' }, t26[8] = { 'c', '3', '3', '7', '0', '7', 'd', '6' }, t27[8] = { 'f', '4', 'd', '5', '0', 'd', '8', '7' }, t28[8] = { '4', '5', '5', 'a', '1', '4', 'e', 'd' }, t29[8] = { 'a', '9', 'e', '3', 'e', '9', '0', '5' }, t30[8] = { 'f', 'c', 'e', 'f', 'a', '3', 'f', '8' }, t31[8] = { '6', '7', '6', 'f', '0', '2', 'd', '9' }, t32[8] = { '8', 'd', '2', 'a', '4', 'c', '8', 'a' }, t33[8] = { 'f', 'f', 'f', 'a', '3', '9', '4', '2' }, t34[8] = { '8', '7', '7', '1', 'f', '6', '8', '1' }, t35[8] = { '6', 'd', '9', 'd', '6', '1', '2', '2' }, t36[8] = { 'f', 'd', 'e', '5', '3', '8', '0', 'c' }, t37[8] = { 'a', '4', 'b', 'e', 'e', 'a', '4', '4' }, t38[8] = { '4', 'b', 'd', 'e', 'c', 'f', 'a', '9' }, t39[8] = { 'f', '6', 'b', 'b', '4', 'b', '6', '0' }, t40[8] = { 'b', 'e', 'b', 'f', 'b', 'c', '7', '0' }, t41[8] = { '2', '8', '9', 'b', '7', 'e', 'c', '6' }, t42[8] = { 'e', 'a', 'a', '1', '2', '7', 'f', 'a' }, t43[8] = { 'd', '4', 'e', 'f', '3', '0', '8', '5' }, t44[8] = { '0', '4', '8', '8', '1', 'd', '0', '5' }, t45[8] = { 'd', '9', 'd', '4', 'd', '0', '3', '9' }, t46[8] = { 'e', '6', 'd', 'b', '9', '9', 'e', '5' }, t47[8] = { '1', 'f', 'a', '2', '7', 'c', 'f', '8' }, t48[8] = { 'c', '4', 'a', 'c', '5', '6', '6', '5' }, t49[8] = { 'f', '4', '2', '9', '2', '2', '4', '4' }, t50[8] = { '4', '3', '2', 'a', 'f', 'f', '9', '7' }, t51[8] = { 'a', 'b', '9', '4', '2', '3', 'a', '7' }, t52[8] = { 'f', 'c', '9', '3', 'a', '0', '3', '9' }, t53[8] = { '6', '5', '5', 'b', '5', '9', 'c', '3' }, t54[8] = { '8', 'f', '0', 'c', 'c', 'c', '9', '2' }, t55[8] = { 'f', 'f', 'e', 'f', 'f', '4', '7', 'd' }, t56[8] = { '8', '5', '8', '4', '5', 'd', 'd', '1' }, t57[8] = { '6', 'f', 'a', '8', '7', 'e', '4', 'f' }, t58[8] = { 'f', 'e', '2', 'c', 'e', '6', 'e', '0' }, t59[8] = { 'a', '3', '0', '1', '4', '3', '1', '4' }, t60[8] = { '4', 'e', '0', '8', '1', '1', 'a', '1' }, t61[8] = { 'f', '7', '5', '3', '7', 'e', '8', '2' }, t62[8] = { 'b', 'd', '3', 'a', 'f', '2', '3', '5' }, t63[8] = { '2', 'a', 'd', '7', 'd', '2', 'b', 'b' }, t64[8] = { 'e', 'b', '8', '6', 'd', '3', '9', '1' }; int in, n = 0, i,j,addup; int md5[512], /*每一大轮m[]的调用顺序*/ m1[16] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 }, m2[16] = { 1, 6, 11, 0, 5, 10, 15, 4, 9, 14, 3, 8, 13, 2, 7, 12 }, m3[16] = { 5, 8, 11, 14, 1, 4, 7, 10, 13, 0, 3, 6, 9, 12, 15, 2 }, m4[16] = { 0, 7, 14, 5, 12, 3, 10, 1, 8, 15, 6, 13, 4, 11, 2, 9 }, /* a[]、b[]、c[]、d[]的初始值(已经过大小端处理) */ /* 把a[]、b[]、c[]、d[]赋值给a1[]、b1[]、c1[]、d1[]*/ a[32] = { 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1 }, a1[32] = { 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1 }, b[32] = { 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1 }, b1[32] = { 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 0, 1 }, c[32] = { 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0 }, c1[32] = { 1, 0, 0, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0 }, d[32] = { 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0 }, d1[32] = { 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0 }; printf("请输入需加密的明文（长度不大于56)\n"); ch = getchar(); while (ch!='\n'&&n