twofish.c

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   LTC_ARGCHK(key  != NULL);
   LTC_ARGCHK(skey != NULL);

   /* invalid arguments? */
   if (num_rounds != 16 && num_rounds != 0) {
      return CRYPT_INVALID_ROUNDS;
   }

   if (keylen != 16 && keylen != 24 && keylen != 32) {
      return CRYPT_INVALID_KEYSIZE;
   }

   /* k = keysize/64 [but since our keysize is in bytes...] */
   k = keylen / 8;

   /* copy the key into M */
   for (x = 0; x < keylen; x++) {
       M[x] = key[x] & 255;
   }

   /* create the S[..] words */
#ifndef TWOFISH_SMALL
   for (x = 0; x < k; x++) {
       rs_mult(M+(x*8), S+(x*4));
   }
#else
   for (x = 0; x < k; x++) {
       rs_mult(M+(x*8), skey->twofish.S+(x*4));
   }
#endif

   /* make subkeys */
   for (x = 0; x < 20; x++) {
       /* A = h(p * 2x, Me) */
       for (y = 0; y < 4; y++) {
           tmp[y] = x+x;
       }
       h_func(tmp, tmp2, M, k, 0);
       LOAD32L(A, tmp2);

       /* B = ROL(h(p * (2x + 1), Mo), 8) */
       for (y = 0; y < 4; y++) {
           tmp[y] = (unsigned char)(x+x+1);
       }
       h_func(tmp, tmp2, M, k, 1);
       LOAD32L(B, tmp2);
       B = ROLc(B, 8);

       /* K[2i]   = A + B */
       skey->twofish.K[x+x] = (A + B) & 0xFFFFFFFFUL;

       /* K[2i+1] = (A + 2B) <<< 9 */
       skey->twofish.K[x+x+1] = ROLc(B + B + A, 9);
   }

#ifndef TWOFISH_SMALL
   /* make the sboxes (large ram variant) */
   if (k == 2) {
        for (x = 0; x < 256; x++) {
           tmpx0 = sbox(0, x);
           tmpx1 = sbox(1, x);
           skey->twofish.S[0][x] = mds_column_mult(sbox(1, (sbox(0, tmpx0 ^ S[0]) ^ S[4])),0);
           skey->twofish.S[1][x] = mds_column_mult(sbox(0, (sbox(0, tmpx1 ^ S[1]) ^ S[5])),1);
           skey->twofish.S[2][x] = mds_column_mult(sbox(1, (sbox(1, tmpx0 ^ S[2]) ^ S[6])),2);
           skey->twofish.S[3][x] = mds_column_mult(sbox(0, (sbox(1, tmpx1 ^ S[3]) ^ S[7])),3);
        }
   } else if (k == 3) {
        for (x = 0; x < 256; x++) {
           tmpx0 = sbox(0, x);
           tmpx1 = sbox(1, x);
           skey->twofish.S[0][x] = mds_column_mult(sbox(1, (sbox(0, sbox(0, tmpx1 ^ S[0]) ^ S[4]) ^ S[8])),0);
           skey->twofish.S[1][x] = mds_column_mult(sbox(0, (sbox(0, sbox(1, tmpx1 ^ S[1]) ^ S[5]) ^ S[9])),1);
           skey->twofish.S[2][x] = mds_column_mult(sbox(1, (sbox(1, sbox(0, tmpx0 ^ S[2]) ^ S[6]) ^ S[10])),2);
           skey->twofish.S[3][x] = mds_column_mult(sbox(0, (sbox(1, sbox(1, tmpx0 ^ S[3]) ^ S[7]) ^ S[11])),3);
        }
   } else {
        for (x = 0; x < 256; x++) {
           tmpx0 = sbox(0, x);
           tmpx1 = sbox(1, x);
           skey->twofish.S[0][x] = mds_column_mult(sbox(1, (sbox(0, sbox(0, sbox(1, tmpx1 ^ S[0]) ^ S[4]) ^ S[8]) ^ S[12])),0);
           skey->twofish.S[1][x] = mds_column_mult(sbox(0, (sbox(0, sbox(1, sbox(1, tmpx0 ^ S[1]) ^ S[5]) ^ S[9]) ^ S[13])),1);
           skey->twofish.S[2][x] = mds_column_mult(sbox(1, (sbox(1, sbox(0, sbox(0, tmpx0 ^ S[2]) ^ S[6]) ^ S[10]) ^ S[14])),2);
           skey->twofish.S[3][x] = mds_column_mult(sbox(0, (sbox(1, sbox(1, sbox(0, tmpx1 ^ S[3]) ^ S[7]) ^ S[11]) ^ S[15])),3);
        }
   }
#else
   /* where to start in the sbox layers */
   /* small ram variant */
   switch (k) {
         case 4 : skey->twofish.start = 0; break;
         case 3 : skey->twofish.start = 1; break; 
         default: skey->twofish.start = 2; break;
   }
#endif
   return CRYPT_OK;
}

#ifdef LTC_CLEAN_STACK
int twofish_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey)
{
   int x;
   x = _twofish_setup(key, keylen, num_rounds, skey);
   burn_stack(sizeof(int) * 7 + sizeof(unsigned char) * 56 + sizeof(ulong32) * 2);
   return x;
}
#endif

/**
  Encrypts a block of text with Twofish
  @param pt The input plaintext (16 bytes)
  @param ct The output ciphertext (16 bytes)
  @param skey The key as scheduled
*/
#ifdef LTC_CLEAN_STACK
static void _twofish_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey)
#else
void twofish_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey)
#endif
{
    ulong32 a,b,c,d,ta,tb,tc,td,t1,t2, *k;
    int r;
#if !defined(TWOFISH_SMALL) && !defined(__GNUC__)
    ulong32 *S1, *S2, *S3, *S4;
#endif    

    LTC_ARGCHK(pt   != NULL);
    LTC_ARGCHK(ct   != NULL);
    LTC_ARGCHK(skey != NULL);
    
#if !defined(TWOFISH_SMALL) && !defined(__GNUC__)
    S1 = skey->twofish.S[0];
    S2 = skey->twofish.S[1];
    S3 = skey->twofish.S[2];
    S4 = skey->twofish.S[3];
#endif    

    LOAD32L(a,&pt[0]); LOAD32L(b,&pt[4]);
    LOAD32L(c,&pt[8]); LOAD32L(d,&pt[12]);
    a ^= skey->twofish.K[0];
    b ^= skey->twofish.K[1];
    c ^= skey->twofish.K[2];
    d ^= skey->twofish.K[3];
    
    k  = skey->twofish.K + 8;
    for (r = 8; r != 0; --r) {
        t2 = g1_func(b, skey);
        t1 = g_func(a, skey) + t2;
        c  = RORc(c ^ (t1 + k[0]), 1);
        d  = ROLc(d, 1) ^ (t2 + t1 + k[1]);
        
        t2 = g1_func(d, skey);
        t1 = g_func(c, skey) + t2;
        a  = RORc(a ^ (t1 + k[2]), 1);
        b  = ROLc(b, 1) ^ (t2 + t1 + k[3]);
        k += 4;
   }

    /* output with "undo last swap" */
    ta = c ^ skey->twofish.K[4];
    tb = d ^ skey->twofish.K[5];
    tc = a ^ skey->twofish.K[6];
    td = b ^ skey->twofish.K[7];

    /* store output */
    STORE32L(ta,&ct[0]); STORE32L(tb,&ct[4]);
    STORE32L(tc,&ct[8]); STORE32L(td,&ct[12]);
}

#ifdef LTC_CLEAN_STACK
void twofish_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey)
{
   _twofish_ecb_encrypt(pt, ct, skey);
   burn_stack(sizeof(ulong32) * 10 + sizeof(int));
}
#endif

/**
  Decrypts a block of text with Twofish
  @param ct The input ciphertext (16 bytes)
  @param pt The output plaintext (16 bytes)
  @param skey The key as scheduled 
*/
#ifdef LTC_CLEAN_STACK
static void _twofish_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey)
#else
void twofish_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey)
#endif
{
    ulong32 a,b,c,d,ta,tb,tc,td,t1,t2, *k;
    int r;
#if !defined(TWOFISH_SMALL) && !defined(__GNUC__)
    ulong32 *S1, *S2, *S3, *S4;
#endif    

    LTC_ARGCHK(pt   != NULL);
    LTC_ARGCHK(ct   != NULL);
    LTC_ARGCHK(skey != NULL);
    
#if !defined(TWOFISH_SMALL) && !defined(__GNUC__)
    S1 = skey->twofish.S[0];
    S2 = skey->twofish.S[1];
    S3 = skey->twofish.S[2];
    S4 = skey->twofish.S[3];
#endif    

    /* load input */
    LOAD32L(ta,&ct[0]); LOAD32L(tb,&ct[4]);
    LOAD32L(tc,&ct[8]); LOAD32L(td,&ct[12]);

    /* undo undo final swap */
    a = tc ^ skey->twofish.K[6];
    b = td ^ skey->twofish.K[7];
    c = ta ^ skey->twofish.K[4];
    d = tb ^ skey->twofish.K[5];

    k = skey->twofish.K + 36;
    for (r = 8; r != 0; --r) {
        t2 = g1_func(d, skey);
        t1 = g_func(c, skey) + t2;
        a = ROLc(a, 1) ^ (t1 + k[2]);
        b = RORc(b ^ (t2 + t1 + k[3]), 1);

        t2 = g1_func(b, skey);
        t1 = g_func(a, skey) + t2;
        c = ROLc(c, 1) ^ (t1 + k[0]);
        d = RORc(d ^ (t2 +  t1 + k[1]), 1);
        k -= 4;
    }

    /* pre-white */
    a ^= skey->twofish.K[0];
    b ^= skey->twofish.K[1];
    c ^= skey->twofish.K[2];
    d ^= skey->twofish.K[3];
    
    /* store */
    STORE32L(a, &pt[0]); STORE32L(b, &pt[4]);
    STORE32L(c, &pt[8]); STORE32L(d, &pt[12]);
}

#ifdef LTC_CLEAN_STACK
void twofish_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey)
{
   _twofish_ecb_decrypt(ct, pt, skey);
   burn_stack(sizeof(ulong32) * 10 + sizeof(int));
}
#endif

/**
  Performs a self-test of the Twofish block cipher
  @return CRYPT_OK if functional, CRYPT_NOP if self-test has been disabled
*/
int twofish_test(void)
{
 #ifndef LTC_TEST
    return CRYPT_NOP;
 #else    
 static const struct { 
     int keylen;
     unsigned char key[32], pt[16], ct[16];
 } tests[] = {
   { 16,
     { 0x9F, 0x58, 0x9F, 0x5C, 0xF6, 0x12, 0x2C, 0x32,
       0xB6, 0xBF, 0xEC, 0x2F, 0x2A, 0xE8, 0xC3, 0x5A },
     { 0xD4, 0x91, 0xDB, 0x16, 0xE7, 0xB1, 0xC3, 0x9E,
       0x86, 0xCB, 0x08, 0x6B, 0x78, 0x9F, 0x54, 0x19 },
     { 0x01, 0x9F, 0x98, 0x09, 0xDE, 0x17, 0x11, 0x85,
       0x8F, 0xAA, 0xC3, 0xA3, 0xBA, 0x20, 0xFB, 0xC3 }
   }, {
     24,
     { 0x88, 0xB2, 0xB2, 0x70, 0x6B, 0x10, 0x5E, 0x36,
       0xB4, 0x46, 0xBB, 0x6D, 0x73, 0x1A, 0x1E, 0x88,
       0xEF, 0xA7, 0x1F, 0x78, 0x89, 0x65, 0xBD, 0x44 },
     { 0x39, 0xDA, 0x69, 0xD6, 0xBA, 0x49, 0x97, 0xD5,
       0x85, 0xB6, 0xDC, 0x07, 0x3C, 0xA3, 0x41, 0xB2 },
     { 0x18, 0x2B, 0x02, 0xD8, 0x14, 0x97, 0xEA, 0x45,
       0xF9, 0xDA, 0xAC, 0xDC, 0x29, 0x19, 0x3A, 0x65 }
   }, { 
     32,
     { 0xD4, 0x3B, 0xB7, 0x55, 0x6E, 0xA3, 0x2E, 0x46,
       0xF2, 0xA2, 0x82, 0xB7, 0xD4, 0x5B, 0x4E, 0x0D,
       0x57, 0xFF, 0x73, 0x9D, 0x4D, 0xC9, 0x2C, 0x1B,
       0xD7, 0xFC, 0x01, 0x70, 0x0C, 0xC8, 0x21, 0x6F },
     { 0x90, 0xAF, 0xE9, 0x1B, 0xB2, 0x88, 0x54, 0x4F,
       0x2C, 0x32, 0xDC, 0x23, 0x9B, 0x26, 0x35, 0xE6 },
     { 0x6C, 0xB4, 0x56, 0x1C, 0x40, 0xBF, 0x0A, 0x97,
       0x05, 0x93, 0x1C, 0xB6, 0xD4, 0x08, 0xE7, 0xFA }
   }
};


 symmetric_key key;
 unsigned char tmp[2][16];
 int err, i, y;
 
 for (i = 0; i < (int)(sizeof(tests)/sizeof(tests[0])); i++) {
    if ((err = twofish_setup(tests[i].key, tests[i].keylen, 0, &key)) != CRYPT_OK) {
       return err;
    }
    twofish_ecb_encrypt(tests[i].pt, tmp[0], &key);
    twofish_ecb_decrypt(tmp[0], tmp[1], &key);
    if (memcmp(tmp[0], tests[i].ct, 16) != 0 || memcmp(tmp[1], tests[i].pt, 16) != 0) {
       return CRYPT_FAIL_TESTVECTOR;
    }
      /* now see if we can encrypt all zero bytes 1000 times, decrypt and come back where we started */
      for (y = 0; y < 16; y++) tmp[0][y] = 0;
      for (y = 0; y < 1000; y++) twofish_ecb_encrypt(tmp[0], tmp[0], &key);
      for (y = 0; y < 1000; y++) twofish_ecb_decrypt(tmp[0], tmp[0], &key);
      for (y = 0; y < 16; y++) if (tmp[0][y] != 0) return CRYPT_FAIL_TESTVECTOR;
 }    
 return CRYPT_OK;
#endif 
}

/** Terminate the context 
   @param skey    The scheduled key
*/
void twofish_done(symmetric_key *skey)
{
}

/**
  Gets suitable key size
  @param keysize [in/out] The length of the recommended key (in bytes).  This function will store the suitable size back in this variable.
  @return CRYPT_OK if the input key size is acceptable.
*/
int twofish_keysize(int *keysize)
{
   LTC_ARGCHK(keysize);
   if (*keysize < 16)
      return CRYPT_INVALID_KEYSIZE;
   if (*keysize < 24) {
      *keysize = 16;
      return CRYPT_OK;
   } else if (*keysize < 32) {
      *keysize = 24;
      return CRYPT_OK;
   } else {
      *keysize = 32;
      return CRYPT_OK;
   }
}

#endif




/* $Source: /cvs/libtom/libtomcrypt/src/ciphers/twofish/twofish.c,v $ */
/* $Revision: 1.8 $ */
/* $Date: 2005/05/05 14:35:58 $ */