encrypt.c

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/* encrypt.c - providing 56 bit DES encryption
   Copyright (C) 1991 Jochen Obalek

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include <time.h>
#include <string.h>
#include <stdlib.h>

#define BS  64
#define BS2 32
#define KS  48
#define KS2 24
#define IS  56
#define IS2 28

static char schluessel[16][KS];


static char PC1[] =
{
  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
};


static char PC2[] =
{
  13, 16, 10, 23,  0,  4,  2, 27,
  14,  5, 20,  9, 22, 18, 11,  3,
  25,  7, 15,  6, 26, 19, 12,  1,
  40, 51, 30, 36, 46, 54, 29, 39,
  50, 44, 32, 47, 43, 48, 38, 55,
  33, 52, 45, 41, 49, 35, 28, 31
};


static char IP[] =
{
  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
};


static char EP[] =
{
   7, 39, 15, 47, 23, 55, 31, 63,
   6, 38, 14, 46, 22, 54, 30, 62,
   5, 37, 13, 45, 21, 53, 29, 61,
   4, 36, 12, 44, 20, 52, 28, 60,
   3, 35, 11, 43, 19, 51, 27, 59,
   2, 34, 10, 42, 18, 50, 26, 58,
   1, 33,  9, 41, 17, 49, 25, 57,
   0, 32,  8, 40, 16, 48, 24, 56
};


static char E0[] =
{
  31,  0,  1,  2,  3,  4,  3,  4,
   5,  6,  7,  8,  7,  8,  9, 10,
  11, 12, 11, 12, 13, 14, 15, 16,
  15, 16, 17, 18, 19, 20, 19, 20,
  21, 22, 23, 24, 23, 24, 25, 26,
  27, 28, 27, 28, 29, 30, 31,  0
};


static char E[KS];


static char PERM[] =
{
  15,  6, 19, 20, 28, 11, 27, 16,
   0, 14, 22, 25,  4, 17, 30,  9,
   1,  7, 23, 13, 31, 26,  2,  8,
  18, 12, 29,  5, 21, 10,  3, 24
};


static char S_BOX[][64] =
{
  {
    14,  0,  4, 15, 13,  7,  1,  4,  2, 14, 15,  2, 11, 13,  8,  1,
     3, 10, 10,  6,  6, 12, 12, 11,  5,  9,  9,  5,  0,  3,  7,  8,
     4, 15,  1, 12, 14,  8,  8,  2, 13,  4,  6,  9,  2,  1, 11,  7,
    15,  5, 12, 11,  9,  3,  7, 14,  3, 10, 10,  0,  5,  6,  0, 13
  },
  {
    15,  3,  1, 13,  8,  4, 14,  7,  6, 15, 11,  2,  3,  8,  4, 14,
     9, 12,  7,  0,  2,  1, 13, 10, 12,  6,  0,  9,  5, 11, 10,  5,
     0, 13, 14,  8,  7, 10, 11,  1, 10,  3,  4, 15, 13,  4,  1,  2,
     5, 11,  8,  6, 12,  7,  6, 12,  9,  0,  3,  5,  2, 14, 15,  9
  },
  {
    10, 13,  0,  7,  9,  0, 14,  9,  6,  3,  3,  4, 15,  6,  5, 10,
     1,  2, 13,  8, 12,  5,  7, 14, 11, 12,  4, 11,  2, 15,  8,  1,
    13,  1,  6, 10,  4, 13,  9,  0,  8,  6, 15,  9,  3,  8,  0,  7,
    11,  4,  1, 15,  2, 14, 12,  3,  5, 11, 10,  5, 14,  2,  7, 12
  },
  {
     7, 13, 13,  8, 14, 11,  3,  5,  0,  6,  6, 15,  9,  0, 10,  3,
     1,  4,  2,  7,  8,  2,  5, 12, 11,  1, 12, 10,  4, 14, 15,  9,
    10,  3,  6, 15,  9,  0,  0,  6, 12, 10, 11,  1,  7, 13, 13,  8,
    15,  9,  1,  4,  3,  5, 14, 11,  5, 12,  2,  7,  8,  2,  4, 14
  },
  {
     2, 14, 12, 11,  4,  2,  1, 12,  7,  4, 10,  7, 11, 13,  6,  1,
     8,  5,  5,  0,  3, 15, 15, 10, 13,  3,  0,  9, 14,  8,  9,  6,
     4, 11,  2,  8,  1, 12, 11,  7, 10,  1, 13, 14,  7,  2,  8, 13,
    15,  6,  9, 15, 12,  0,  5,  9,  6, 10,  3,  4,  0,  5, 14,  3
  },
  {
    12, 10,  1, 15, 10,  4, 15,  2,  9,  7,  2, 12,  6,  9,  8,  5,
     0,  6, 13,  1,  3, 13,  4, 14, 14,  0,  7, 11,  5,  3, 11,  8,
     9,  4, 14,  3, 15,  2,  5, 12,  2,  9,  8,  5, 12, 15,  3, 10,
     7, 11,  0, 14,  4,  1, 10,  7,  1,  6, 13,  0, 11,  8,  6, 13
  },
  {
     4, 13, 11,  0,  2, 11, 14,  7, 15,  4,  0,  9,  8,  1, 13, 10,
     3, 14, 12,  3,  9,  5,  7, 12,  5,  2, 10, 15,  6,  8,  1,  6,
     1,  6,  4, 11, 11, 13, 13,  8, 12,  1,  3,  4,  7, 10, 14,  7,
    10,  9, 15,  5,  6,  0,  8, 15,  0, 14,  5,  2,  9,  3,  2, 12
  },
  {
    13,  1,  2, 15,  8, 13,  4,  8,  6, 10, 15,  3, 11,  7,  1,  4,
    10, 12,  9,  5,  3,  6, 14, 11,  5,  0,  0, 14, 12,  9,  7,  2,
     7,  2, 11,  1,  4, 14,  1,  7,  9,  4, 12, 10, 14,  8,  2, 13,
     0, 15,  6, 12, 10,  9, 13,  0, 15,  3,  3,  5,  5,  6,  8, 11
  }
};

static void 
perm (a, e, pc, n)
     register char *a, *e;
     register char *pc;
     int n;
{
  for (; n--; pc++, a++)
    *a = e[*pc];
}

static void 
crypt_main (nachr_l, nachr_r, schl)
     register char *nachr_l, *nachr_r;
     register char *schl;
{
  char tmp[KS];
  register int sbval;
  register char *tp = tmp;
  register char *e = E;
  register int i, j;

  for (i = 0; i < 8; i++)
    {
      for (j = 0, sbval = 0; j < 6; j++)
	sbval = (sbval << 1) | (nachr_r[*e++] ^ *schl++);
      sbval = S_BOX[i][sbval];
      for (tp += 4, j = 4; j--; sbval >>= 1)
	*--tp = sbval & 1;
      tp += 4;
    }

  e = PERM;
  for (i = 0; i < BS2; i++)
    *nachr_l++ ^= tmp[*e++];
}

void 
encrypt (char *nachr, int decr)
{
  char (*schl)[KS] = decr ? schluessel + 15 : schluessel;
  char tmp[BS];
  int i;

  perm (tmp, nachr, IP, BS);

  for (i = 8; i--;)
    {
      crypt_main (tmp, tmp + BS2, *schl);
      if (decr)
	schl--;
      else
	schl++;
      crypt_main (tmp + BS2, tmp, *schl);
      if (decr)
	schl--;
      else
	schl++;
    }

  perm (nachr, tmp, EP, BS);
}

void 
setkey (char *schl)
{
  char tmp1[IS];
  register unsigned int ls = 0x7efc;
  register int i, j, k;
  register int shval = 0;
  register char *akt_schl;

  memcpy (E, E0, KS);
  perm (tmp1, schl, PC1, IS);

  for (i = 0; i < 16; i++)
    {
      shval += 1 + (ls & 1);
      akt_schl = schluessel[i];
      for (j = 0; j < KS; j++)
	{
	  if ((k = PC2[j]) >= IS2)
	    {
	      if ((k += shval) >= IS)
		k = (k - IS2) % IS2 + IS2;
	    }
	  else if ((k += shval) >= IS2)
	    k %= IS2;
	  *akt_schl++ = tmp1[k];
	}
      ls >>= 1;
    }
}

char *
crypt (const char *wort, const char *salt)
{
  static char retkey[14];
  char key[BS + 2];
  char *k;
  int tmp, keybyte;
  int i, j;

  memset (key, 0, BS + 2);

  for (k = key, i = 0; i < BS; i++)
    {
      if (!(keybyte = *wort++))
	break;
      k += 7;
      for (j = 0; j < 7; j++, i++)
	{
	  *--k = keybyte & 1;
	  keybyte >>= 1;
	}
      k += 8;
    }

  setkey (key);
  memset (key, 0, BS + 2);

  for (k = E, i = 0; i < 2; i++)
    {
      retkey[i] = keybyte = *salt++;
      if (keybyte > 'Z')
	keybyte -= 'a' - 'Z' - 1;
      if (keybyte > '9')
	keybyte -= 'A' - '9' - 1;
      keybyte -= '.';

      for (j = 0; j < 6; j++, keybyte >>= 1, k++)
	{
	  if (!(keybyte & 1))
	    continue;
	  tmp = *k;
	  *k = k[24];
	  k[24] = tmp;
	}
    }

  for (i = 0; i < 25; i++)
    encrypt (key, 0);

  for (k = key, i = 0; i < 11; i++)
    {
      for (j = keybyte = 0; j < 6; j++)
	{
	  keybyte <<= 1;
	  keybyte |= *k++;
	}

      keybyte += '.';
      if (keybyte > '9')
	keybyte += 'A' - '9' - 1;
      if (keybyte > 'Z')
	keybyte += 'a' - 'Z' - 1;
      retkey[i + 2] = keybyte;
    }

  retkey[i + 2] = 0;

  if (!retkey[1])
    retkey[1] = *retkey;

  return retkey;
}