libtomcrypt/src/ciphers/twofish/twofish.c - platform/external/dropbear - Git at Google

 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
  *
  * LibTomCrypt is a library that provides various cryptographic
  * algorithms in a highly modular and flexible manner.
  *
  * The library is free for all purposes without any express
  * guarantee it works.
  *
  * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
  */

  /**
    @file twofish.c
    Implementation of Twofish by Tom St Denis
  */
 #include "tomcrypt.h"

 #ifdef TWOFISH

 /* first TWOFISH_ALL_TABLES must ensure TWOFISH_TABLES is defined */
 #ifdef TWOFISH_ALL_TABLES
 #ifndef TWOFISH_TABLES
 #define TWOFISH_TABLES
 #endif
 #endif

 const struct ltc_cipher_descriptor twofish_desc =
 {
     "twofish",
     7,
     16, 32, 16, 16,
     &twofish_setup,
     &twofish_ecb_encrypt,
     &twofish_ecb_decrypt,
     &twofish_test,
     &twofish_done,
     &twofish_keysize,
     NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
 };

 /* the two polynomials */
 #define MDS_POLY          0x169
 #define RS_POLY           0x14D

 /* The 4x4 MDS Linear Transform */
 #if 0
 static const unsigned char MDS[4][4] = {
     { 0x01, 0xEF, 0x5B, 0x5B },
     { 0x5B, 0xEF, 0xEF, 0x01 },
     { 0xEF, 0x5B, 0x01, 0xEF },
     { 0xEF, 0x01, 0xEF, 0x5B }
 };
 #endif

 /* The 4x8 RS Linear Transform */
 static const unsigned char RS[4][8] = {
     { 0x01, 0xA4, 0x55, 0x87, 0x5A, 0x58, 0xDB, 0x9E },
     { 0xA4, 0x56, 0x82, 0xF3, 0X1E, 0XC6, 0X68, 0XE5 },
     { 0X02, 0XA1, 0XFC, 0XC1, 0X47, 0XAE, 0X3D, 0X19 },
     { 0XA4, 0X55, 0X87, 0X5A, 0X58, 0XDB, 0X9E, 0X03 }
 };

 /* sbox usage orderings */
 static const unsigned char qord[4][5] = {
    { 1, 1, 0, 0, 1 },
    { 0, 1, 1, 0, 0 },
    { 0, 0, 0, 1, 1 },
    { 1, 0, 1, 1, 0 }
 };

 #ifdef TWOFISH_TABLES

 #include "twofish_tab.c"

 #define sbox(i, x) ((ulong32)SBOX[i][(x)&255])

 #else

 /* The Q-box tables */
 static const unsigned char qbox[2][4][16] = {
 {
    { 0x8, 0x1, 0x7, 0xD, 0x6, 0xF, 0x3, 0x2, 0x0, 0xB, 0x5, 0x9, 0xE, 0xC, 0xA, 0x4 },
    { 0xE, 0XC, 0XB, 0X8, 0X1, 0X2, 0X3, 0X5, 0XF, 0X4, 0XA, 0X6, 0X7, 0X0, 0X9, 0XD },
    { 0XB, 0XA, 0X5, 0XE, 0X6, 0XD, 0X9, 0X0, 0XC, 0X8, 0XF, 0X3, 0X2, 0X4, 0X7, 0X1 },
    { 0XD, 0X7, 0XF, 0X4, 0X1, 0X2, 0X6, 0XE, 0X9, 0XB, 0X3, 0X0, 0X8, 0X5, 0XC, 0XA }
 },
 {
    { 0X2, 0X8, 0XB, 0XD, 0XF, 0X7, 0X6, 0XE, 0X3, 0X1, 0X9, 0X4, 0X0, 0XA, 0XC, 0X5 },
    { 0X1, 0XE, 0X2, 0XB, 0X4, 0XC, 0X3, 0X7, 0X6, 0XD, 0XA, 0X5, 0XF, 0X9, 0X0, 0X8 },
    { 0X4, 0XC, 0X7, 0X5, 0X1, 0X6, 0X9, 0XA, 0X0, 0XE, 0XD, 0X8, 0X2, 0XB, 0X3, 0XF },
    { 0xB, 0X9, 0X5, 0X1, 0XC, 0X3, 0XD, 0XE, 0X6, 0X4, 0X7, 0XF, 0X2, 0X0, 0X8, 0XA }
 }
 };

 /* computes S_i[x] */
 #ifdef LTC_CLEAN_STACK
 static ulong32 _sbox(int i, ulong32 x)
 #else
 static ulong32 sbox(int i, ulong32 x)
 #endif
 {
    unsigned char a0,b0,a1,b1,a2,b2,a3,b3,a4,b4,y;

    /* a0,b0 = [x/16], x mod 16 */
    a0 = (unsigned char)((x>>4)&15);
    b0 = (unsigned char)((x)&15);

    /* a1 = a0 ^ b0 */
    a1 = a0 ^ b0;

    /* b1 = a0 ^ ROR(b0, 1) ^ 8a0 */
    b1 = (a0 ^ ((b0<<3)|(b0>>1)) ^ (a0<<3)) & 15;

    /* a2,b2 = t0[a1], t1[b1] */
    a2 = qbox[i][0][(int)a1];
    b2 = qbox[i][1][(int)b1];

    /* a3 = a2 ^ b2 */
    a3 = a2 ^ b2;

    /* b3 = a2 ^ ROR(b2, 1) ^ 8a2 */
    b3 = (a2 ^ ((b2<<3)|(b2>>1)) ^ (a2<<3)) & 15;

    /* a4,b4 = t2[a3], t3[b3] */
    a4 = qbox[i][2][(int)a3];
    b4 = qbox[i][3][(int)b3];

    /* y = 16b4 + a4 */
    y = (b4 << 4) + a4;

    /* return result */
    return (ulong32)y;
 }

 #ifdef LTC_CLEAN_STACK
 static ulong32 sbox(int i, ulong32 x)
 {
    ulong32 y;
    y = _sbox(i, x);
    burn_stack(sizeof(unsigned char) * 11);
    return y;
 }
 #endif /* LTC_CLEAN_STACK */

 #endif /* TWOFISH_TABLES */

 /* computes ab mod p */
 static ulong32 gf_mult(ulong32 a, ulong32 b, ulong32 p)
 {
    ulong32 result, B[2], P[2];

    P[1] = p;
    B[1] = b;
    result = P[0] = B[0] = 0;

    /* unrolled branchless GF multiplier */
    result ^= B[a&1]; a >>= 1;  B[1] = P[B[1]>>7] ^ (B[1] << 1);
    result ^= B[a&1]; a >>= 1;  B[1] = P[B[1]>>7] ^ (B[1] << 1);
    result ^= B[a&1]; a >>= 1;  B[1] = P[B[1]>>7] ^ (B[1] << 1);
    result ^= B[a&1]; a >>= 1;  B[1] = P[B[1]>>7] ^ (B[1] << 1);
    result ^= B[a&1]; a >>= 1;  B[1] = P[B[1]>>7] ^ (B[1] << 1);
    result ^= B[a&1]; a >>= 1;  B[1] = P[B[1]>>7] ^ (B[1] << 1);
    result ^= B[a&1]; a >>= 1;  B[1] = P[B[1]>>7] ^ (B[1] << 1);
    result ^= B[a&1];

    return result;
 }

 /* computes [y0 y1 y2 y3] = MDS . [x0] */
 #ifndef TWOFISH_TABLES
 static ulong32 mds_column_mult(unsigned char in, int col)
 {
    ulong32 x01, x5B, xEF;

    x01 = in;
    x5B = gf_mult(in, 0x5B, MDS_POLY);
    xEF = gf_mult(in, 0xEF, MDS_POLY);

    switch (col) {
        case 0:
           return (x01 << 0 ) |
                  (x5B << 8 ) |
                  (xEF << 16) |
                  (xEF << 24);
        case 1:
           return (xEF << 0 ) |
                  (xEF << 8 ) |
                  (x5B << 16) |
                  (x01 << 24);
        case 2:
           return (x5B << 0 ) |
                  (xEF << 8 ) |
                  (x01 << 16) |
                  (xEF << 24);
        case 3:
           return (x5B << 0 ) |
                  (x01 << 8 ) |
                  (xEF << 16) |
                  (x5B << 24);
    }
    /* avoid warnings, we'd never get here normally but just to calm compiler warnings... */
    return 0;
 }

 #else /* !TWOFISH_TABLES */

 #define mds_column_mult(x, i) mds_tab[i][x]

 #endif /* TWOFISH_TABLES */

 /* Computes [y0 y1 y2 y3] = MDS . [x0 x1 x2 x3] */
 static void mds_mult(const unsigned char *in, unsigned char *out)
 {
   int x;
   ulong32 tmp;
   for (tmp = x = 0; x < 4; x++) {
       tmp ^= mds_column_mult(in[x], x);
   }
   STORE32L(tmp, out);
 }

 #ifdef TWOFISH_ALL_TABLES
 /* computes [y0 y1 y2 y3] = RS . [x0 x1 x2 x3 x4 x5 x6 x7] */
 static void rs_mult(const unsigned char *in, unsigned char *out)
 {
    ulong32 tmp;
    tmp = rs_tab0[in[0]] ^ rs_tab1[in[1]] ^ rs_tab2[in[2]] ^ rs_tab3[in[3]] ^
          rs_tab4[in[4]] ^ rs_tab5[in[5]] ^ rs_tab6[in[6]] ^ rs_tab7[in[7]];
    STORE32L(tmp, out);
 }

 #else /* !TWOFISH_ALL_TABLES */

 /* computes [y0 y1 y2 y3] = RS . [x0 x1 x2 x3 x4 x5 x6 x7] */
 static void rs_mult(const unsigned char *in, unsigned char *out)
 {
   int x, y;
   for (x = 0; x < 4; x++) {
       out[x] = 0;
       for (y = 0; y < 8; y++) {
           out[x] ^= gf_mult(in[y], RS[x][y], RS_POLY);
       }
   }
 }

 #endif

 /* computes h(x) */
 static void h_func(const unsigned char *in, unsigned char *out, unsigned char *M, int k, int offset)
 {
   int x;
   unsigned char y[4];
   for (x = 0; x < 4; x++) {
       y[x] = in[x];
  }
   switch (k) {
      case 4:
             y[0] = (unsigned char)(sbox(1, (ulong32)y[0]) ^ M[4 * (6 + offset) + 0]);
             y[1] = (unsigned char)(sbox(0, (ulong32)y[1]) ^ M[4 * (6 + offset) + 1]);
             y[2] = (unsigned char)(sbox(0, (ulong32)y[2]) ^ M[4 * (6 + offset) + 2]);
             y[3] = (unsigned char)(sbox(1, (ulong32)y[3]) ^ M[4 * (6 + offset) + 3]);
      case 3:
             y[0] = (unsigned char)(sbox(1, (ulong32)y[0]) ^ M[4 * (4 + offset) + 0]);
             y[1] = (unsigned char)(sbox(1, (ulong32)y[1]) ^ M[4 * (4 + offset) + 1]);
             y[2] = (unsigned char)(sbox(0, (ulong32)y[2]) ^ M[4 * (4 + offset) + 2]);
             y[3] = (unsigned char)(sbox(0, (ulong32)y[3]) ^ M[4 * (4 + offset) + 3]);
      case 2:
             y[0] = (unsigned char)(sbox(1, sbox(0, sbox(0, (ulong32)y[0]) ^ M[4 * (2 + offset) + 0]) ^ M[4 * (0 + offset) + 0]));
             y[1] = (unsigned char)(sbox(0, sbox(0, sbox(1, (ulong32)y[1]) ^ M[4 * (2 + offset) + 1]) ^ M[4 * (0 + offset) + 1]));
             y[2] = (unsigned char)(sbox(1, sbox(1, sbox(0, (ulong32)y[2]) ^ M[4 * (2 + offset) + 2]) ^ M[4 * (0 + offset) + 2]));
             y[3] = (unsigned char)(sbox(0, sbox(1, sbox(1, (ulong32)y[3]) ^ M[4 * (2 + offset) + 3]) ^ M[4 * (0 + offset) + 3]));
   }
   mds_mult(y, out);
 }

 #ifndef TWOFISH_SMALL

 /* for GCC we don't use pointer aliases */
 #if defined(__GNUC__)
     #define S1 skey->twofish.S[0]
     #define S2 skey->twofish.S[1]
     #define S3 skey->twofish.S[2]
     #define S4 skey->twofish.S[3]
 #endif

 /* the G function */
 #define g_func(x, dum)  (S1[byte(x,0)] ^ S2[byte(x,1)] ^ S3[byte(x,2)] ^ S4[byte(x,3)])
 #define g1_func(x, dum) (S2[byte(x,0)] ^ S3[byte(x,1)] ^ S4[byte(x,2)] ^ S1[byte(x,3)])

 #else

 #ifdef LTC_CLEAN_STACK
 static ulong32 _g_func(ulong32 x, symmetric_key *key)
 #else
 static ulong32 g_func(ulong32 x, symmetric_key *key)
 #endif
 {
    unsigned char g, i, y, z;
    ulong32 res;

    res = 0;
    for (y = 0; y < 4; y++) {
        z = key->twofish.start;

        /* do unkeyed substitution */
        g = sbox(qord[y][z++], (x >> (8*y)) & 255);

        /* first subkey */
        i = 0;

        /* do key mixing+sbox until z==5 */
        while (z != 5) {
           g = g ^ key->twofish.S[4*i++ + y];
           g = sbox(qord[y][z++], g);
        }

        /* multiply g by a column of the MDS */
        res ^= mds_column_mult(g, y);
    }
    return res;
 }

 #define g1_func(x, key) g_func(ROLc(x, 8), key)

 #ifdef LTC_CLEAN_STACK
 static ulong32 g_func(ulong32 x, symmetric_key *key)
 {
     ulong32 y;
     y = _g_func(x, key);
     burn_stack(sizeof(unsigned char) * 4 + sizeof(ulong32));
     return y;
 }
 #endif /* LTC_CLEAN_STACK */

 #endif /* TWOFISH_SMALL */

  /**
     Initialize the Twofish block cipher
     @param key The symmetric key you wish to pass
     @param keylen The key length in bytes
     @param num_rounds The number of rounds desired (0 for default)
     @param skey The key in as scheduled by this function.
     @return CRYPT_OK if successful
  */
 #ifdef LTC_CLEAN_STACK
 static int _twofish_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey)
 #else
 int twofish_setup(const unsigned char *key, int keylen, int num_rounds, symmetric_key *skey)
 #endif
 {
 #ifndef TWOFISH_SMALL
    unsigned char S[4*4], tmpx0, tmpx1;
 #endif
    int k, x, y;
    unsigned char tmp[4], tmp2[4], M[8*4];
    ulong32 A, B;

    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 = (unsigned char)sbox(0, x);
            tmpx1 = (unsigned char)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 = (unsigned char)sbox(0, x);
            tmpx1 = (unsigned char)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 = (unsigned char)sbox(0, x);
            tmpx1 = (unsigned char)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
   @return CRYPT_OK if successful
 */
 #ifdef LTC_CLEAN_STACK
 static int _twofish_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey)
 #else
 int 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]);

     return CRYPT_OK;
 }

 #ifdef LTC_CLEAN_STACK
 int twofish_ecb_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_key *skey)
 {
    int err = _twofish_ecb_encrypt(pt, ct, skey);
    burn_stack(sizeof(ulong32) * 10 + sizeof(int));
    return err;
 }
 #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
   @return CRYPT_OK if successful
 */
 #ifdef LTC_CLEAN_STACK
 static int _twofish_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey)
 #else
 int 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]);
     return CRYPT_OK;
 }

 #ifdef LTC_CLEAN_STACK
 int twofish_ecb_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_key *skey)
 {
    int err =_twofish_ecb_decrypt(ct, pt, skey);
    burn_stack(sizeof(ulong32) * 10 + sizeof(int));
    return err;
 }
 #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 (XMEMCMP(tmp[0], tests[i].ct, 16) != 0 || XMEMCMP(tmp[1], tests[i].pt, 16) != 0) {
 #if 0
        printf("Twofish failed test %d, %d, %d\n", i, XMEMCMP(tmp[0], tests[i].ct, 16), XMEMCMP(tmp[1], tests[i].pt, 16));
 #endif
        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: 1.14 $ */
 /* $Date: 2006/12/04 21:34:03 $ */
	/* LibTomCrypt, modular cryptographic library -- Tom St Denis
	*
	* LibTomCrypt is a library that provides various cryptographic
	* algorithms in a highly modular and flexible manner.
	*
	* The library is free for all purposes without any express
	* guarantee it works.
	*
	* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
	*/

	/**
	@file twofish.c
	Implementation of Twofish by Tom St Denis
	*/
	#include "tomcrypt.h"

	#ifdef TWOFISH

	/* first TWOFISH_ALL_TABLES must ensure TWOFISH_TABLES is defined */
	#ifdef TWOFISH_ALL_TABLES
	#ifndef TWOFISH_TABLES
	#define TWOFISH_TABLES
	#endif
	#endif

	const struct ltc_cipher_descriptor twofish_desc =
	{
	"twofish",
	7,
	16, 32, 16, 16,
	&twofish_setup,
	&twofish_ecb_encrypt,
	&twofish_ecb_decrypt,
	&twofish_test,
	&twofish_done,
	&twofish_keysize,
	NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
	};

	/* the two polynomials */
	#define MDS_POLY 0x169
	#define RS_POLY 0x14D

	/* The 4x4 MDS Linear Transform */
	#if 0
	static const unsigned char MDS[4][4] = {
	{ 0x01, 0xEF, 0x5B, 0x5B },
	{ 0x5B, 0xEF, 0xEF, 0x01 },
	{ 0xEF, 0x5B, 0x01, 0xEF },
	{ 0xEF, 0x01, 0xEF, 0x5B }
	};
	#endif

	/* The 4x8 RS Linear Transform */
	static const unsigned char RS[4][8] = {
	{ 0x01, 0xA4, 0x55, 0x87, 0x5A, 0x58, 0xDB, 0x9E },
	{ 0xA4, 0x56, 0x82, 0xF3, 0X1E, 0XC6, 0X68, 0XE5 },
	{ 0X02, 0XA1, 0XFC, 0XC1, 0X47, 0XAE, 0X3D, 0X19 },
	{ 0XA4, 0X55, 0X87, 0X5A, 0X58, 0XDB, 0X9E, 0X03 }
	};

	/* sbox usage orderings */
	static const unsigned char qord[4][5] = {
	{ 1, 1, 0, 0, 1 },
	{ 0, 1, 1, 0, 0 },
	{ 0, 0, 0, 1, 1 },
	{ 1, 0, 1, 1, 0 }
	};

	#ifdef TWOFISH_TABLES

	#include "twofish_tab.c"

	#define sbox(i, x) ((ulong32)SBOX[i][(x)&255])

	#else

	/* The Q-box tables */
	static const unsigned char qbox[2][4][16] = {
	{
	{ 0x8, 0x1, 0x7, 0xD, 0x6, 0xF, 0x3, 0x2, 0x0, 0xB, 0x5, 0x9, 0xE, 0xC, 0xA, 0x4 },
	{ 0xE, 0XC, 0XB, 0X8, 0X1, 0X2, 0X3, 0X5, 0XF, 0X4, 0XA, 0X6, 0X7, 0X0, 0X9, 0XD },
	{ 0XB, 0XA, 0X5, 0XE, 0X6, 0XD, 0X9, 0X0, 0XC, 0X8, 0XF, 0X3, 0X2, 0X4, 0X7, 0X1 },
	{ 0XD, 0X7, 0XF, 0X4, 0X1, 0X2, 0X6, 0XE, 0X9, 0XB, 0X3, 0X0, 0X8, 0X5, 0XC, 0XA }
	},
	{
	{ 0X2, 0X8, 0XB, 0XD, 0XF, 0X7, 0X6, 0XE, 0X3, 0X1, 0X9, 0X4, 0X0, 0XA, 0XC, 0X5 },
	{ 0X1, 0XE, 0X2, 0XB, 0X4, 0XC, 0X3, 0X7, 0X6, 0XD, 0XA, 0X5, 0XF, 0X9, 0X0, 0X8 },
	{ 0X4, 0XC, 0X7, 0X5, 0X1, 0X6, 0X9, 0XA, 0X0, 0XE, 0XD, 0X8, 0X2, 0XB, 0X3, 0XF },
	{ 0xB, 0X9, 0X5, 0X1, 0XC, 0X3, 0XD, 0XE, 0X6, 0X4, 0X7, 0XF, 0X2, 0X0, 0X8, 0XA }
	}
	};

	/* computes S_i[x] */
	#ifdef LTC_CLEAN_STACK
	static ulong32 _sbox(int i, ulong32 x)
	#else
	static ulong32 sbox(int i, ulong32 x)
	#endif
	{
	unsigned char a0,b0,a1,b1,a2,b2,a3,b3,a4,b4,y;

	/* a0,b0 = [x/16], x mod 16 */
	a0 = (unsigned char)((x>>4)&15);
	b0 = (unsigned char)((x)&15);

	/* a1 = a0 ^ b0 */
	a1 = a0 ^ b0;

	/* b1 = a0 ^ ROR(b0, 1) ^ 8a0 */
	b1 = (a0 ^ ((b0<<3)\|(b0>>1)) ^ (a0<<3)) & 15;

	/* a2,b2 = t0[a1], t1[b1] */
	a2 = qbox[i][0][(int)a1];
	b2 = qbox[i][1][(int)b1];

	/* a3 = a2 ^ b2 */
	a3 = a2 ^ b2;

	/* b3 = a2 ^ ROR(b2, 1) ^ 8a2 */
	b3 = (a2 ^ ((b2<<3)\|(b2>>1)) ^ (a2<<3)) & 15;

	/* a4,b4 = t2[a3], t3[b3] */
	a4 = qbox[i][2][(int)a3];
	b4 = qbox[i][3][(int)b3];

	/* y = 16b4 + a4 */
	y = (b4 << 4) + a4;

	/* return result */
	return (ulong32)y;
	}

	#ifdef LTC_CLEAN_STACK
	static ulong32 sbox(int i, ulong32 x)
	{
	ulong32 y;
	y = _sbox(i, x);
	burn_stack(sizeof(unsigned char) * 11);
	return y;
	}
	#endif /* LTC_CLEAN_STACK */

	#endif /* TWOFISH_TABLES */

	/* computes ab mod p */
	static ulong32 gf_mult(ulong32 a, ulong32 b, ulong32 p)
	{
	ulong32 result, B[2], P[2];

	P[1] = p;
	B[1] = b;
	result = P[0] = B[0] = 0;

	/* unrolled branchless GF multiplier */
	result ^= B[a&1]; a >>= 1; B[1] = P[B[1]>>7] ^ (B[1] << 1);
	result ^= B[a&1]; a >>= 1; B[1] = P[B[1]>>7] ^ (B[1] << 1);
	result ^= B[a&1]; a >>= 1; B[1] = P[B[1]>>7] ^ (B[1] << 1);
	result ^= B[a&1]; a >>= 1; B[1] = P[B[1]>>7] ^ (B[1] << 1);
	result ^= B[a&1]; a >>= 1; B[1] = P[B[1]>>7] ^ (B[1] << 1);
	result ^= B[a&1]; a >>= 1; B[1] = P[B[1]>>7] ^ (B[1] << 1);
	result ^= B[a&1]; a >>= 1; B[1] = P[B[1]>>7] ^ (B[1] << 1);
	result ^= B[a&1];

	return result;
	}

	/* computes [y0 y1 y2 y3] = MDS . [x0] */
	#ifndef TWOFISH_TABLES
	static ulong32 mds_column_mult(unsigned char in, int col)
	{
	ulong32 x01, x5B, xEF;

	x01 = in;
	x5B = gf_mult(in, 0x5B, MDS_POLY);
	xEF = gf_mult(in, 0xEF, MDS_POLY);

	switch (col) {
	case 0:
	return (x01 << 0 ) \|
	(x5B << 8 ) \|
	(xEF << 16) \|
	(xEF << 24);
	case 1:
	return (xEF << 0 ) \|
	(xEF << 8 ) \|
	(x5B << 16) \|
	(x01 << 24);
	case 2:
	return (x5B << 0 ) \|
	(xEF << 8 ) \|
	(x01 << 16) \|
	(xEF << 24);
	case 3:
	return (x5B << 0 ) \|
	(x01 << 8 ) \|
	(xEF << 16) \|
	(x5B << 24);
	}
	/* avoid warnings, we'd never get here normally but just to calm compiler warnings... */
	return 0;
	}

	#else /* !TWOFISH_TABLES */

	#define mds_column_mult(x, i) mds_tab[i][x]

	#endif /* TWOFISH_TABLES */

	/* Computes [y0 y1 y2 y3] = MDS . [x0 x1 x2 x3] */
	static void mds_mult(const unsigned char in, unsigned char out)
	{
	int x;
	ulong32 tmp;
	for (tmp = x = 0; x < 4; x++) {
	tmp ^= mds_column_mult(in[x], x);
	}
	STORE32L(tmp, out);
	}

	#ifdef TWOFISH_ALL_TABLES
	/* computes [y0 y1 y2 y3] = RS . [x0 x1 x2 x3 x4 x5 x6 x7] */
	static void rs_mult(const unsigned char in, unsigned char out)
	{
	ulong32 tmp;
	tmp = rs_tab0[in[0]] ^ rs_tab1[in[1]] ^ rs_tab2[in[2]] ^ rs_tab3[in[3]] ^
	rs_tab4[in[4]] ^ rs_tab5[in[5]] ^ rs_tab6[in[6]] ^ rs_tab7[in[7]];
	STORE32L(tmp, out);
	}

	#else /* !TWOFISH_ALL_TABLES */

	/* computes [y0 y1 y2 y3] = RS . [x0 x1 x2 x3 x4 x5 x6 x7] */
	static void rs_mult(const unsigned char in, unsigned char out)
	{
	int x, y;
	for (x = 0; x < 4; x++) {
	out[x] = 0;
	for (y = 0; y < 8; y++) {
	out[x] ^= gf_mult(in[y], RS[x][y], RS_POLY);
	}
	}
	}

	#endif

	/* computes h(x) */
	static void h_func(const unsigned char in, unsigned char out, unsigned char *M, int k, int offset)
	{
	int x;
	unsigned char y[4];
	for (x = 0; x < 4; x++) {
	y[x] = in[x];
	}
	switch (k) {
	case 4:
	y[0] = (unsigned char)(sbox(1, (ulong32)y[0]) ^ M[4 * (6 + offset) + 0]);
	y[1] = (unsigned char)(sbox(0, (ulong32)y[1]) ^ M[4 * (6 + offset) + 1]);
	y[2] = (unsigned char)(sbox(0, (ulong32)y[2]) ^ M[4 * (6 + offset) + 2]);
	y[3] = (unsigned char)(sbox(1, (ulong32)y[3]) ^ M[4 * (6 + offset) + 3]);
	case 3:
	y[0] = (unsigned char)(sbox(1, (ulong32)y[0]) ^ M[4 * (4 + offset) + 0]);
	y[1] = (unsigned char)(sbox(1, (ulong32)y[1]) ^ M[4 * (4 + offset) + 1]);
	y[2] = (unsigned char)(sbox(0, (ulong32)y[2]) ^ M[4 * (4 + offset) + 2]);
	y[3] = (unsigned char)(sbox(0, (ulong32)y[3]) ^ M[4 * (4 + offset) + 3]);
	case 2:
	y[0] = (unsigned char)(sbox(1, sbox(0, sbox(0, (ulong32)y[0]) ^ M[4 * (2 + offset) + 0]) ^ M[4 * (0 + offset) + 0]));
	y[1] = (unsigned char)(sbox(0, sbox(0, sbox(1, (ulong32)y[1]) ^ M[4 * (2 + offset) + 1]) ^ M[4 * (0 + offset) + 1]));
	y[2] = (unsigned char)(sbox(1, sbox(1, sbox(0, (ulong32)y[2]) ^ M[4 * (2 + offset) + 2]) ^ M[4 * (0 + offset) + 2]));
	y[3] = (unsigned char)(sbox(0, sbox(1, sbox(1, (ulong32)y[3]) ^ M[4 * (2 + offset) + 3]) ^ M[4 * (0 + offset) + 3]));
	}
	mds_mult(y, out);
	}

	#ifndef TWOFISH_SMALL

	/* for GCC we don't use pointer aliases */
	#if defined(__GNUC__)
	#define S1 skey->twofish.S[0]
	#define S2 skey->twofish.S[1]
	#define S3 skey->twofish.S[2]
	#define S4 skey->twofish.S[3]
	#endif

	/* the G function */
	#define g_func(x, dum) (S1[byte(x,0)] ^ S2[byte(x,1)] ^ S3[byte(x,2)] ^ S4[byte(x,3)])
	#define g1_func(x, dum) (S2[byte(x,0)] ^ S3[byte(x,1)] ^ S4[byte(x,2)] ^ S1[byte(x,3)])

	#else

	#ifdef LTC_CLEAN_STACK
	static ulong32 _g_func(ulong32 x, symmetric_key *key)
	#else
	static ulong32 g_func(ulong32 x, symmetric_key *key)
	#endif
	{
	unsigned char g, i, y, z;
	ulong32 res;

	res = 0;
	for (y = 0; y < 4; y++) {
	z = key->twofish.start;

	/* do unkeyed substitution */
	g = sbox(qord[y][z++], (x >> (8*y)) & 255);

	/* first subkey */
	i = 0;

	/* do key mixing+sbox until z==5 */
	while (z != 5) {
	g = g ^ key->twofish.S[4*i++ + y];
	g = sbox(qord[y][z++], g);
	}

	/* multiply g by a column of the MDS */
	res ^= mds_column_mult(g, y);
	}
	return res;
	}

	#define g1_func(x, key) g_func(ROLc(x, 8), key)

	#ifdef LTC_CLEAN_STACK
	static ulong32 g_func(ulong32 x, symmetric_key *key)
	{
	ulong32 y;
	y = _g_func(x, key);
	burn_stack(sizeof(unsigned char) * 4 + sizeof(ulong32));
	return y;
	}
	#endif /* LTC_CLEAN_STACK */

	#endif /* TWOFISH_SMALL */

	/**
	Initialize the Twofish block cipher
	@param key The symmetric key you wish to pass
	@param keylen The key length in bytes
	@param num_rounds The number of rounds desired (0 for default)
	@param skey The key in as scheduled by this function.
	@return CRYPT_OK if successful
	*/
	#ifdef LTC_CLEAN_STACK
	static int _twofish_setup(const unsigned char key, int keylen, int num_rounds, symmetric_key skey)
	#else
	int twofish_setup(const unsigned char key, int keylen, int num_rounds, symmetric_key skey)
	#endif
	{
	#ifndef TWOFISH_SMALL
	unsigned char S[4*4], tmpx0, tmpx1;
	#endif
	int k, x, y;
	unsigned char tmp[4], tmp2[4], M[8*4];
	ulong32 A, B;

	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+(x8), S+(x4));
	}
	#else
	for (x = 0; x < k; x++) {
	rs_mult(M+(x8), skey->twofish.S+(x4));
	}
	#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 = (unsigned char)sbox(0, x);
	tmpx1 = (unsigned char)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 = (unsigned char)sbox(0, x);
	tmpx1 = (unsigned char)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 = (unsigned char)sbox(0, x);
	tmpx1 = (unsigned char)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
	@return CRYPT_OK if successful
	*/
	#ifdef LTC_CLEAN_STACK
	static int _twofish_ecb_encrypt(const unsigned char pt, unsigned char ct, symmetric_key *skey)
	#else
	int 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]);

	return CRYPT_OK;
	}

	#ifdef LTC_CLEAN_STACK
	int twofish_ecb_encrypt(const unsigned char pt, unsigned char ct, symmetric_key *skey)
	{
	int err = _twofish_ecb_encrypt(pt, ct, skey);
	burn_stack(sizeof(ulong32) * 10 + sizeof(int));
	return err;
	}
	#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
	@return CRYPT_OK if successful
	*/
	#ifdef LTC_CLEAN_STACK
	static int _twofish_ecb_decrypt(const unsigned char ct, unsigned char pt, symmetric_key *skey)
	#else
	int 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]);
	return CRYPT_OK;
	}

	#ifdef LTC_CLEAN_STACK
	int twofish_ecb_decrypt(const unsigned char ct, unsigned char pt, symmetric_key *skey)
	{
	int err =_twofish_ecb_decrypt(ct, pt, skey);
	burn_stack(sizeof(ulong32) * 10 + sizeof(int));
	return err;
	}
	#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 (XMEMCMP(tmp[0], tests[i].ct, 16) != 0 \|\| XMEMCMP(tmp[1], tests[i].pt, 16) != 0) {
	#if 0
	printf("Twofish failed test %d, %d, %d\n", i, XMEMCMP(tmp[0], tests[i].ct, 16), XMEMCMP(tmp[1], tests[i].pt, 16));
	#endif
	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: 1.14 $ */
	/* $Date: 2006/12/04 21:34:03 $ */