#include "des.h"

//全局变量定义

/*
DES加密流程：
1.输入8字节要加密数据，然后把8字节转换成位形式存储于64个字节中（注：高位存低字节，低位存高字节中，详情参看下面贴出的代码Byte2Bits函数）；
2.按IP表对64位进行转换，得到新的64位。（参：Permutation函数）
3.把64位分成左右各32位。（参：DivideLR函数）
注：4至9步共循环16次(i<16)
4.按E表对R（右32位）扩展到48位。
5.把扩展后的R(48位)与key（密钥）进行异或操作。（参：ByteXor函数）
6.按Sbox（s1-s8）对第5步得到的48位进行转换，得到最终的32位。（参：PermuSbox函数）
7.把这个32位和P表置换。
8.然后再与L（左32位）进行异或。
9.组合LR为新的64位。
10.4-9步的16次循环后得到最终的64位，然后与IP-1表进行置换，完成一次加密。
11.把64位转为8字节，这就是加密后的8字节。 （参：Bits2Byte函数）
*/
//局部变量定义
const unsigned char initial_tr[64] =
{
 57, 49, 41, 33, 25, 17,  9,  1,
 59, 51, 43, 35, 27, 19, 11,  3,
 61, 53, 45, 37, 29, 21, 13,  5,
 63, 55, 47, 39, 31, 23, 15,  7,
 56, 48, 40, 32, 24, 16,  8,  0,
 58, 50, 42, 34, 26, 18, 10,  2,
 60, 52, 44, 36, 28, 20, 12,  4,
 62, 54, 46, 38, 30, 22, 14,  6
};
const unsigned char final_tr[64] =
{
 39,  7, 47, 15, 55, 23, 63, 31,
 38,  6, 46, 14, 54, 22, 62, 30,
 37,  5, 45, 13, 53, 21, 61, 29,
 36,  4, 44, 12, 52, 20, 60, 28,
 35,  3, 43, 11, 51, 19, 59, 27,
 34,  2, 42, 10, 50, 18, 58, 26,
 33,  1, 41,  9, 49, 17, 57, 25,
 32,  0, 40,  8, 48, 16, 56, 24
};
const unsigned char swap[64] =
{
 33, 34, 35, 36, 37, 38, 39, 40,
 41, 42, 43, 44, 45, 46, 47, 48,
 49, 50, 51, 52, 53, 54, 55, 56,
 57, 58, 59, 60, 61, 62, 63, 64,
  1,  2,  3,  4,  5,  6,  7,  8,
  9, 10, 11, 12, 13, 14, 15, 16,
 17, 18, 19, 20, 21, 22, 23, 24,
 25, 26, 27, 28, 29, 30, 31, 32
};
const unsigned char key_tr1[56] =
{
 56, 48, 40, 32, 24, 16,  8,
  0, 57, 49, 41, 33, 25, 17,
  9,  1, 58, 50, 42, 34, 26,
 18, 10,  2, 59, 51, 43, 35,
 62, 54, 46, 38, 30, 22, 14,
  6, 61, 53, 45, 37, 29, 21,
 13,  5, 60, 52, 44, 36, 28,
 20, 12,  4, 27, 19, 11,  3
};
const unsigned char key_tr2[64] =
{
 0,  0, 13,  4, 16, 10, 23,  0,
 0,  0,  2,  9, 27, 14,  5, 20,
 0,  0, 22,  7, 18, 11,  3, 25,
 0,  0, 15,  1,  6, 26, 19, 12,
 0,  0, 40, 54, 51, 30, 36, 46,
 0,  0, 29, 47, 39, 50, 44, 32,
 0,  0, 43, 52, 48, 38, 55, 33,
 0,  0, 45, 31, 41, 49, 35, 28
};
const unsigned char etr[64] =
{
 0,  0, 31,  4,  0,  1,  2,  3,
 0,  0,  3,  8,  4,  5,  6,  7,
 0,  0,  7, 12,  8,  9, 10, 11,
 0,  0, 11, 16, 12, 13, 14, 15,
 0,  0, 15, 20, 16, 17, 18, 19,
 0,  0, 19, 24, 20, 21, 22, 23,
 0,  0, 23, 28, 24, 25, 26, 27,
 0,  0, 27,  0, 28, 29, 30, 31
};
const unsigned char ptr[32] =
{
 31, 14, 39, 44, 60, 23, 55, 36,
  4, 30, 46, 53, 12, 37, 62, 21,
  5, 15, 47, 29, 63, 54,  6, 20,
 38, 28, 61, 13, 45, 22,  7, 52
};
const unsigned char s[8][64] =
{
 {
  14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
   0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
   4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
  15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13
 },
 {
  15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
   3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
   0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
  13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9
 },
 {
  10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
  13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
  13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
   1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12
 },
 {
   7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
  13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
  10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
   3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14
 },
 {
   2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
  14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
   4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
  11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3
 },
 {
  12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
  10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
   9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
   4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7, 6,  0,  8,  13
 },
 {
   4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
  13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
   1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
   6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12
 },
 {
  13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
   1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
   7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
   2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11
 }
};
const unsigned char rots[16] =
{
 1,  1,  2,  2,  2,  2,  2,  2,  1,  2,  2,  2,  2,  2,  2,  1
};
const unsigned char bit_msk[8] =
{
 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01
};
unsigned char sub_keys[16][8]; //sub_keys[16][8]
unsigned char main_key[8];

//局部函数声明
static  void    transpose (unsigned char*, unsigned char*, const unsigned char*, unsigned char);
static  void    rotate_l (unsigned char*);
static  void    compute_subkeys (unsigned char*);
static  void    f(unsigned char*, unsigned char*, unsigned char*);

//局部函数定义
void transpose(unsigned char *idata, unsigned char *odata, const unsigned char *tbl, unsigned char n)
{
  const unsigned char *tab_adr;
  int i, bi_idx;
  tab_adr = &bit_msk[0];
  i = 0;
 
  do
    {odata[i++] = 0;}
  while (i < 8);
  i = 0;
  do
  {
    bi_idx = *tbl++;
    if (idata[bi_idx>>3] & tab_adr[bi_idx & 7])
    {
      odata[i>>3] |= tab_adr[i & 7];
    }
  }while (++i < n);
}

void rotate_l(unsigned char *key)
{
  unsigned char str_x[8];
  unsigned char i;
  for (i=0; i < 8; ++i) str_x[i] = key[i];
  for (i=0; i < 7; ++i)
  {
    key[i] = (key[i] << 1);
    if ((i < 6) && ((str_x[i+1] & 128) == 128))
    key[i] |= 1;
  }
  if (str_x[0] & 0x80 )
    key[3] |= 0x10;
  else
    key[3] &= ~0x10;
  if (str_x[3] & 0x08 )
    key[6] |= 0x01;
  else
    key[6] &= ~0x01;
}

void compute_subkeys(unsigned char *key)
{
  unsigned char i, j, ikey[8], okey[8];
  for (i=0; i < 8; ++i)
  {
    main_key[i] = key[i];
  }
 
  transpose(key, ikey, key_tr1, 56);
 
  for (i=0; i < 16; ++i)
  {
    for (j=0; j < rots[i]; ++j) {rotate_l(ikey);}
    transpose(ikey, okey, key_tr2,  64);
    for (j=0; j < 8; ++j) {sub_keys[i][j] = okey[j];}
  }
}

void f(unsigned char *skey, unsigned char *a_str, unsigned char *x_str)
{
  unsigned char e_str[8], y_str[8], z_str[8];
  unsigned char k;
  transpose(a_str, e_str, etr, 64);
  for (k=0; k < 8; ++k)
  {
    y_str[k] = (e_str[k] ^ skey[k]) & 63;
    z_str[k] = s[k] [y_str[k]];
  }
  transpose(z_str, x_str, ptr, 32);
}

/*******************全局函数定义*****************/
void des(unsigned char *plain_strng, unsigned char *key, unsigned char d, unsigned char *ciph_strng)
{
  unsigned char a_str[8], b_str[8], x_str[8];
  unsigned char i, j, *pkey, temp;
  for (i = 0; i < 8 ; ++i)
  {
    if (key[i] != main_key[i])
    {
      compute_subkeys(key);
      i = 7;
    }
  }
 
  transpose(plain_strng, a_str, initial_tr, 64);
  for (i=1; i < 17; ++i)
  {
    for (j=0; j < 8; ++j){b_str[j] = a_str[j];}
    
		if (!d)           /*enchipher*/
      pkey = &sub_keys[i-1][0];
    else                /*dechipher*/
     pkey = &sub_keys[16-i][0];
  
    for (j=0; j < 4; ++j){a_str[j] = b_str[j+4];}
   
    f(pkey, a_str, x_str);
   
    for (j=0; j < 4; ++j) {a_str[j+4] = b_str[j] ^ x_str[j];}
  }
    
  temp = a_str[0]; a_str[0] = a_str[4]; a_str[4] = temp;
  temp = a_str[1]; a_str[1] = a_str[5]; a_str[5] = temp;
  temp = a_str[2]; a_str[2] = a_str[6]; a_str[6] = temp;
  temp = a_str[3]; a_str[3] = a_str[7]; a_str[7] = temp;
  transpose(a_str, ciph_strng, final_tr, 64);
}