des.c

/* des.c
 *
 * The des block cipher.
 *
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2001 Niels Mller
 *  
 * The nettle library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * The nettle library 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 Lesser General Public
 * License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*	des - fast & portable DES encryption & decryption.
 *	Copyright (C) 1992  Dana L. How
 *	Please see the file `descore.README' for the complete copyright notice.
 */

#if HAVE_CONFIG_H
# include "config.h"
#endif

#include <assert.h>

#include "des.h"

#include "desCode.h"

/* various tables */

static const uint32_t
des_keymap[] = {
#include	"keymap.h"
};

static const uint8_t
rotors[] = {
#include	"rotors.h"
};

static ENCRYPT(DesSmallFipsEncrypt,TEMPSMALL, LOADFIPS,KEYMAPSMALL,SAVEFIPS)
static DECRYPT(DesSmallFipsDecrypt,TEMPSMALL, LOADFIPS,KEYMAPSMALL,SAVEFIPS)

/* If parity bits are used, keys should have odd parity. We use a
   small table, to not waste any memory on this fairly obscure DES
   feature. */

static const unsigned
parity_16[16] =
{ 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0 };

#define PARITY(x) (parity_16[(x)&0xf] ^ parity_16[((x)>>4) & 0xf])

int
des_check_parity(unsigned length, const uint8_t *key)
{
  unsigned i;
  for (i = 0; i<length; i++)
    if (!PARITY(key[i]))
      return 0;

  return 1;
}

void
des_fix_parity(unsigned length, uint8_t *dst,
	       const uint8_t *src)
{
  unsigned i;
  for (i = 0; i<length; i++)
    dst[i] = src[i] ^ PARITY(src[i]) ^ 1;
}

/* Weak and semiweak keys, excluding parity:
 *
 * 00 00 00 00  00 00 00 00
 * 7f 7f 7f 7f  7f 7f 7f 7f 
 * 0f 0f 0f 0f  07 07 07 07
 * 70 70 70 70  78 78 78 78
 *
 * 00 7f 00 7f  00 7f 00 7f
 * 7f 00 7f 00  7f 00 7f 00
 *
 * 0f 70 0f 70  07 78 07 78
 * 70 0f 70 0f  78 07 78 07
 *
 * 00 70 00 70  00 78 00 78
 * 70 00 70 00  78 00 78 00
 *
 * 0f 7f 0f 7f  07 7f 07 7f
 * 7f 0f 7f 0f  7f 07 7f 07
 *
 * 00 0f 00 0f  00 07 00 07
 * 0f 00 0f 00  07 00 07 00
 *
 * 70 7f 70 7f  78 7f 78 7f
 * 7f 70 7f 70  7f 78 7f 78
 */

static int
des_weak_p(const uint8_t *key)
{
  /* Hash function generated using gperf. */
  static const unsigned char asso_values[0x81] =
    {
      16,  9, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26,  6,  2, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
      26, 26,  3,  1, 26, 26, 26, 26, 26, 26,
      26, 26, 26, 26, 26, 26, 26,  0,  0
    };

  static const int8_t weak_key_hash[26][4] =
    {
      /*  0 */ {0x7f,0x7f, 0x7f,0x7f},
      /*  1 */ {0x7f,0x70, 0x7f,0x78},
      /*  2 */ {0x7f,0x0f, 0x7f,0x07},
      /*  3 */ {0x70,0x7f, 0x78,0x7f},
      /*  4 */ {0x70,0x70, 0x78,0x78},
      /*  5 */ {0x70,0x0f, 0x78,0x07},
      /*  6 */ {0x0f,0x7f, 0x07,0x7f},
      /*  7 */ {0x0f,0x70, 0x07,0x78},
      /*  8 */ {0x0f,0x0f, 0x07,0x07},
      /*  9 */ {0x7f,0x00, 0x7f,0x00},
      /* 10 */ {-1,-1,-1,-1},
      /* 11 */ {-1,-1,-1,-1},
      /* 12 */ {0x70,0x00, 0x78,0x00},
      /* 13 */ {-1,-1,-1,-1},
      /* 14 */ {-1,-1,-1,-1},
      /* 15 */ {0x0f,0x00, 0x07,0x00},
      /* 16 */ {0x00,0x7f, 0x00,0x7f},
      /* 17 */ {0x00,0x70, 0x00,0x78},
      /* 18 */ {0x00,0x0f, 0x00,0x07},
      /* 19 */ {-1,-1,-1,-1},
      /* 20 */ {-1,-1,-1,-1},
      /* 21 */ {-1,-1,-1,-1},
      /* 22 */ {-1,-1,-1,-1},
      /* 23 */ {-1,-1,-1,-1},
      /* 24 */ {-1,-1,-1,-1},
      /* 25 */ {0x00,0x00, 0x00,0x00}
    };

  int8_t k0 = key[0] >> 1;
  int8_t k1 = key[1] >> 1;

  unsigned hash = asso_values[k1 + 1] + asso_values[k0];
  const int8_t *candidate = weak_key_hash[hash];

  if (hash > 25)
    return 0;
  if (k0 != candidate[0]
      || k1 != candidate[1])
    return 0;
  
  if ( (key[2] >> 1) != k0
       || (key[3] >> 1) != k1)
    return 0;

  k0 = key[4] >> 1;
  k1 = key[5] >> 1;
  if (k0 != candidate[2]
      || k1 != candidate[3])
    return 0;
  if ( (key[6] >> 1) != k0
       || (key[7] >> 1) != k1)
    return 0;

  return 1;
}

int
des_set_key(struct des_ctx *ctx, const uint8_t *key)
{
  register uint32_t n, w;
  register char * b0, * b1;
  char bits0[56], bits1[56];
  uint32_t *method;
  const uint8_t *k;

  /* explode the bits */
  n = 56;
  b0 = bits0;
  b1 = bits1;
  k = key;
  do {
    w = (256 | *k++) << 2;
    do {
      --n;
      b1[n] = 8 & w;
      w >>= 1;
      b0[n] = 4 & w;
    } while ( w >= 16 );
  } while ( n );

  /* put the bits in the correct places */
  n = 16;
  k = rotors;
  method = ctx->key;
  
  do {
    w   = (b1[k[ 0   ]] | b0[k[ 1   ]]) << 4;
    w  |= (b1[k[ 2   ]] | b0[k[ 3   ]]) << 2;
    w  |=  b1[k[ 4   ]] | b0[k[ 5   ]];
    w <<= 8;
    w  |= (b1[k[ 6   ]] | b0[k[ 7   ]]) << 4;
    w  |= (b1[k[ 8   ]] | b0[k[ 9   ]]) << 2;
    w  |=  b1[k[10   ]] | b0[k[11   ]];
    w <<= 8;
    w  |= (b1[k[12   ]] | b0[k[13   ]]) << 4;
    w  |= (b1[k[14   ]] | b0[k[15   ]]) << 2;
    w  |=  b1[k[16   ]] | b0[k[17   ]];
    w <<= 8;
    w  |= (b1[k[18   ]] | b0[k[19   ]]) << 4;
    w  |= (b1[k[20   ]] | b0[k[21   ]]) << 2;
    w  |=  b1[k[22   ]] | b0[k[23   ]];

    method[0] = w;

    w   = (b1[k[ 0+24]] | b0[k[ 1+24]]) << 4;
    w  |= (b1[k[ 2+24]] | b0[k[ 3+24]]) << 2;
    w  |=  b1[k[ 4+24]] | b0[k[ 5+24]];
    w <<= 8;
    w  |= (b1[k[ 6+24]] | b0[k[ 7+24]]) << 4;
    w  |= (b1[k[ 8+24]] | b0[k[ 9+24]]) << 2;
    w  |=  b1[k[10+24]] | b0[k[11+24]];
    w <<= 8;
    w  |= (b1[k[12+24]] | b0[k[13+24]]) << 4;
    w  |= (b1[k[14+24]] | b0[k[15+24]]) << 2;
    w  |=  b1[k[16+24]] | b0[k[17+24]];
    w <<= 8;
    w  |= (b1[k[18+24]] | b0[k[19+24]]) << 4;
    w  |= (b1[k[20+24]] | b0[k[21+24]]) << 2;
    w  |=  b1[k[22+24]] | b0[k[23+24]];

    ROR(w, 4, 28);		/* could be eliminated */
    method[1] = w;

    k	+= 48;
    method	+= 2;
  } while ( --n );

  return !des_weak_p (key);
}

void
des_encrypt(const struct des_ctx *ctx,
	    unsigned length, uint8_t *dst,
	    const uint8_t *src)
{
  assert(!(length % DES_BLOCK_SIZE));
  
  while (length)
    {
      DesSmallFipsEncrypt(dst, ctx->key, src);
      length -= DES_BLOCK_SIZE;
      src += DES_BLOCK_SIZE;
      dst += DES_BLOCK_SIZE;
    }
}

void
des_decrypt(const struct des_ctx *ctx,
	    unsigned length, uint8_t *dst,
	    const uint8_t *src)
{
  assert(!(length % DES_BLOCK_SIZE));

  while (length)
    {
      DesSmallFipsDecrypt(dst, ctx->key, src);
      length -= DES_BLOCK_SIZE;
      src += DES_BLOCK_SIZE;
      dst += DES_BLOCK_SIZE;
    }
}