/*--------------------------------------------------------------------------------
DES.C: DES Algorithm Program from the Book Applied Cryptography, Bruce Schneier
--------------------------------------------------------------------------------*/

#define EN0   0      /* MODE == encrypt */
#define DE1   1      /* MODE == decrypt */

#include <stdio.h>
#include <reg51.h>

typedef struct {
  unsigned long ek[32];
 unsigned long dk[32];
} des_ctx;

extern void deskey(unsigned char *, short);
/*                  hexkey[8]     MODE
 * Sets the internal key register according to the hexadecimal
 * key contained in the 8 bytes of hexkey, according to the DES,
 * for encryption or decryption according to MODE.
 */

extern void usekey(unsigned long *);
/*                cookedkey[32]
 * Loads the internal key register with the data in cookedkey.
 */

extern void cpkey(unsigned long *);
/*               cookedkey[32]
 * Copies the contents of the internal key register into the storage
 * located at &cookedkey[0].
 */

extern void des(unsigned char *, unsigned char *);
/*                from[8]         to[8]
 * Encrypts/Decrypts (according to the key currently loaded in the
 * internal key register) one block of eight bytes at address 'from'
 * into the block at address 'to'.  They can be the same.
 */

static void scrunch(unsigned char *, unsigned long *);
static void unscrun(unsigned long *, unsigned char *);
static void desfunc(unsigned long *, unsigned long *);
static void cookey(unsigned long *);

static unsigned long KnL[32] = { 0L };
static unsigned long KnR[32] = { 0L };
static unsigned long Kn3[32] = { 0L };
static unsigned char Df_Key[24] = {
       0x01,0x23,0x45,0x67,0x89,0xab,0xcd,0xef,
       0xfe,0xdc,0xba,0x98,0x76,0x54,0x32,0x10,
       0x89,0xab,0xcd,0xef,0x01,0x23,0x45,0x67 };

static unsigned short bytebit[8]    = {
       0200, 0100, 040, 020, 010, 04, 02, 01 };

static unsigned long bigbyte[24] = {
       0x800000L,    0x400000L,     0x200000L,    0x100000L,
       0x80000L,     0x40000L,      0x20000L,     0x10000L,
       0x8000L,      0x4000L,       0x2000L,      0x1000L,
       0x800L,              0x400L,               0x200L,              0x100L,
       0x80L,               0x40L,                0x20L,               0x10L,
       0x8L,         0x4L,          0x2L,         0x1L   };

/* Use the key schedule specified in the Standard (ANSI X3.92-1981). */

static unsigned char pc1[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 };

static unsigned char totrot[16] = {
       1,2,4,6,8,10,12,14,15,17,19,21,23,25,27,28 };

static unsigned char pc2[48] = {
       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 };

void deskey(unsigned char *key, short edf)  {
  /* Thanks to James Gillogly & Phil Karn! */
  register int i, j, l, m, n;
  unsigned char pc1m[56], pcr[56];
  unsigned long kn[32];

  for ( j = 0; j < 56; j++ ) {
    l = pc1[j];
    m = l & 07;
    pc1m[j] = (key[l >> 3] & bytebit[m]) ? 1 : 0;
  }
  for( i = 0; i < 16; i++ ) {
    if( edf == DE1 ) m = (15 - i) << 1;
    else             m = i << 1;
    n = m + 1;
    kn[m] = kn[n] = 0L;
    for( j = 0; j < 28; j++ ) {
      l = j + totrot[i];
      if( l < 28 ) pcr[j] = pc1m[l];
      else pcr[j] = pc1m[l - 28];
    }
    for( j = 28; j < 56; j++ ) {
      l = j + totrot[i];
      if( l < 56 ) pcr[j] = pc1m[l];
      else         pcr[j] = pc1m[l - 28];
    }
    for( j = 0; j < 24; j++ ) {
      if( pcr[pc2[j]] )    kn[m] |= bigbyte[j];
      if( pcr[pc2[j+24]] ) kn[n] |= bigbyte[j];
    }
  }
  cookey(kn);
}

static void cookey(unsigned long *raw1)  {
  register unsigned long *cook, *raw0;
  unsigned long dough[32];
  register int i;

  cook = dough;
  for( i = 0; i < 16; i++, raw1++ ) {
    raw0 = raw1++;
    *cook   = (*raw0 & 0x00fc0000L) << 6;
    *cook  |= (*raw0 & 0x00000fc0L) << 10;
    *cook  |= (*raw1 & 0x00fc0000L) >> 10;
    *cook++|= (*raw1 & 0x00000fc0L) >> 6;
    *cook   = (*raw0 & 0x0003f000L) << 12;
    *cook  |= (*raw0 & 0x0000003fL) << 16;
    *cook  |= (*raw1 & 0x0003f000L) >> 4;
    *cook++       |= (*raw1 & 0x0000003fL);
  }
  usekey(dough);
}

void cpkey(unsigned long *into)  {
  register unsigned long *from, *endp;

  from = KnL, endp = &KnL[32];
  while( from < endp ) *into++ = *from++;
}

void usekey(unsigned long *from)  {
  register unsigned long *to, *endp;

  to = KnL, endp = &KnL[32];
  while( to < endp ) *to++ = *from++;
}

#if 0
void des(unsigned char *inblock, unsigned char *outblock)  {
  unsigned long work[2];

  scrunch(inblock, work);
  desfunc(work, KnL);
  unscrun(work, outblock);
}
#endif

static void scrunch(unsigned char *outof, unsigned long *into)  {
  *into   = (*outof++ & 0xffL) << 24;
  *into  |= (*outof++ & 0xffL) << 16;
  *into  |= (*outof++ & 0xffL) << 8;
  *into++ |= (*outof++ & 0xffL);
  *into   = (*outof++ & 0xffL) << 24;
  *into  |= (*outof++ & 0xffL) << 16;
  *into  |= (*outof++ & 0xffL) << 8;
  *into  |= (*outof   & 0xffL);
}

static void unscrun(unsigned long *outof, unsigned char *into)  {
  *into++ = (*outof >> 24) & 0xffL;
  *into++ = (*outof >> 16) & 0xffL;
  *into++ = (*outof >>  8) & 0xffL;
  *into++ =  *outof++      & 0xffL;
  *into++ = (*outof >> 24) & 0xffL;
  *into++ = (*outof >> 16) & 0xffL;
  *into++ = (*outof >>  8) & 0xffL;
  *into   =  *outof     & 0xffL;
}

static unsigned long SP1[64] = {
  0x01010400L, 0x00000000L, 0x00010000L, 0x01010404L,
  0x01010004L, 0x00010404L, 0x00000004L, 0x00010000L,
  0x00000400L, 0x01010400L, 0x01010404L, 0x00000400L,
  0x01000404L, 0x01010004L, 0x01000000L, 0x00000004L,
  0x00000404L, 0x01000400L, 0x01000400L, 0x00010400L,
  0x00010400L, 0x01010000L, 0x01010000L, 0x01000404L,
  0x00010004L, 0x01000004L, 0x01000004L, 0x00010004L,
  0x00000000L, 0x00000404L, 0x00010404L, 0x01000000L,
  0x00010000L, 0x01010404L, 0x00000004L, 0x01010000L,
  0x01010400L, 0x01000000L, 0x01000000L, 0x00000400L,
  0x01010004L, 0x00010000L, 0x00010400L, 0x01000004L,
  0x00000400L, 0x00000004L, 0x01000404L, 0x00010404L,
  0x01010404L, 0x00010004L, 0x01010000L, 0x01000404L,
  0x01000004L, 0x00000404L, 0x00010404L, 0x01010400L,
  0x00000404L, 0x01000400L, 0x01000400L, 0x00000000L,
  0x00010004L, 0x00010400L, 0x00000000L, 0x01010004L };

static unsigned long SP2[64] = {
  0x80108020L, 0x80008000L, 0x00008000L, 0x00108020L,
  0x00100000L, 0x00000020L, 0x80100020L, 0x80008020L,
  0x80000020L, 0x80108020L, 0x80108000L, 0x80000000L,
  0x80008000L, 0x00100000L, 0x00000020L, 0x80100020L,
  0x00108000L, 0x00100020L, 0x80008020L, 0x00000000L,
  0x80000000L, 0x00008000L, 0x00108020L, 0x80100000L,
  0x00100020L, 0x80000020L, 0x00000000L, 0x00108000L,
  0x00008020L, 0x80108000L, 0x80100000L, 0x00008020L,
  0x00000000L, 0x00108020L, 0x80100020L, 0x00100000L,
  0x80008020L, 0x80100000L, 0x80108000L, 0x00008000L,
  0x80100000L, 0x80008000L, 0x00000020L, 0x80108020L,
  0x00108020L, 0x00000020L, 0x00008000L, 0x80000000L,
  0x00008020L, 0x80108000L, 0x00100000L, 0x80000020L,
  0x00100020L, 0x80008020L, 0x80000020L, 0x00100020L,
  0x00108000L, 0x00000000L, 0x80008000L, 0x00008020L,
  0x80000000L, 0x80100020L, 0x80108020L, 0x00108000L };

static unsigned long SP3[64] = {
  0x00000208L, 0x08020200L, 0x00000000L, 0x08020008L,
  0x08000200L, 0x00000000L, 0x00020208L, 0x08000200L,
  0x00020008L, 0x08000008L, 0x08000008L, 0x00020000L,
  0x08020208L, 0x00020008L, 0x08020000L, 0x00000208L,
  0x08000000L, 0x00000008L, 0x08020200L, 0x00000200L,
  0x00020200L, 0x08020000L, 0x08020008L, 0x00020208L,
  0x08000208L, 0x00020200L, 0x00020000L, 0x08000208L,
  0x00000008L, 0x08020208L, 0x00000200L, 0x08000000L,
  0x08020200L, 0x08000000L, 0x00020008L, 0x00000208L,
  0x00020000L, 0x08020200L, 0x08000200L, 0x00000000L,
  0x00000200L, 0x00020008L, 0x08020208L, 0x08000200L,
  0x08000008L, 0x00000200L, 0x00000000L, 0x08020008L,
  0x08000208L, 0x00020000L, 0x08000000L, 0x08020208L,
  0x00000008L, 0x00020208L, 0x00020200L, 0x08000008L,
  0x08020000L, 0x08000208L, 0x00000208L, 0x08020000L,
  0x00020208L, 0x00000008L, 0x08020008L, 0x00020200L };

static unsigned long SP4[64] = {
  0x00802001L, 0x00002081L, 0x00002081L, 0x00000080L,
  0x00802080L, 0x00800081L, 0x00800001L, 0x00002001L,
  0x00000000L, 0x00802000L, 0x00802000L, 0x00802081L,
  0x00000081L, 0x00000000L, 0x00800080L, 0x00800001L,
  0x00000001L, 0x00002000L, 0x00800000L, 0x00802001L,
  0x00000080L, 0x00800000L, 0x00002001L, 0x00002080L,
  0x00800081L, 0x00000001L, 0x00002080L, 0x00800080L,
  0x00002000L, 0x00802080L, 0x00802081L, 0x00000081L,
  0x00800080L, 0x00800001L, 0x00802000L, 0x00802081L,
  0x00000081L, 0x00000000L, 0x00000000L, 0x00802000L,