/* 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;
}