/* This is an independent implementation of the encryption algorithm:   */
/*                                                                      */
/*         Twofish by Bruce Schneier and colleagues                     */
/*                                                                      */
/* which is a candidate algorithm in the Advanced Encryption Standard   */
/* programme of the US National Institute of Standards and Technology.  */
/*                                                                      */
/* Copyright in this implementation is held by Dr B R Gladman but I     */
/* hereby give permission for its free direct or derivative use subject */
/* to acknowledgment of its origin and compliance with any conditions   */
/* that the originators of t he algorithm place on its exploitation.     */
/*                                                                      */
/* My thanks to Doug Whiting and Niels Ferguson for comments that led   */
/* to improvements in this implementation.                              */
/*                                                                      */
/* Dr Brian Gladman (gladman@seven77.demon.co.uk) 14th January 1999     */

#include <mix/aes.h>

#define Q_TABLES
#define M_TABLE
#define MK_TABLE
#define ONE_STEP

u4byte k_len;
u4byte l4_key[40];
u4byte s_key[4];

/* finite field arithmetic for GF(2**8) with the modular    */
/* polynomial x^8 + x^6 + x^5 + x^3 + 1 (0x169)             */

#define G_M 0x0169

u1byte tab_5b[4] =
{0, G_M >> 2, G_M >> 1, (G_M >> 1) ^ (G_M >> 2)};
u1byte tab_ef[4] =
{0, (G_M >> 1) ^ (G_M >> 2), G_M >> 1, G_M >> 2};

#define ffm_01(x)    (x)
#define ffm_5b(x)   ((x) ^ ((x) >> 2) ^ tab_5b[(x) & 3])
#define ffm_ef(x)   ((x) ^ ((x) >> 1) ^ ((x) >> 2) ^ tab_ef[(x) & 3])

u1byte ror4[16] =
{0, 8, 1, 9, 2, 10, 3, 11, 4, 12, 5, 13, 6, 14, 7, 15};
u1byte ashx[16] =
{0, 9, 2, 11, 4, 13, 6, 15, 8, 1, 10, 3, 12, 5, 14, 7};

u1byte qt0[2][16] =
{
  {8, 1, 7, 13, 6, 15, 3, 2, 0, 11, 5, 9, 14, 12, 10, 4},
  {2, 8, 11, 13, 15, 7, 6, 14, 3, 1, 9, 4, 0, 10, 12, 5}
};

u1byte qt1[2][16] =
{
  {14, 12, 11, 8, 1, 2, 3, 5, 15, 4, 10, 6, 7, 0, 9, 13},
  {1, 14, 2, 11, 4, 12, 3, 7, 6, 13, 10, 5, 15, 9, 0, 8}
};

u1byte qt2[2][16] =
{
  {11, 10, 5, 14, 6, 13, 9, 0, 12, 8, 15, 3, 2, 4, 7, 1},
  {4, 12, 7, 5, 1, 6, 9, 10, 0, 14, 13, 8, 2, 11, 3, 15}
};

u1byte qt3[2][16] =
{
  {13, 7, 15, 4, 1, 2, 6, 14, 9, 11, 3, 0, 8, 5, 12, 10},
  {11, 9, 5, 1, 12, 3, 13, 14, 6, 4, 7, 15, 2, 0, 8, 10}
};

u1byte
qp(const u4byte n, const u1byte x)
{
  u1byte a0, a1, a2, a3, a4, b0, b1, b2, b3, b4;

  a0 = x >> 4;
  b0 = x & 15;
  a1 = a0 ^ b0;
  b1 = ror4[b0] ^ ashx[a0];
  a2 = qt0[n][a1];
  b2 = qt1[n][b1];
  a3 = a2 ^ b2;
  b3 = ror4[b2] ^ ashx[a2];
  a4 = qt2[n][a3];
  b4 = qt3[n][b3];
  return (b4 << 4) | a4;
};

#ifdef  Q_TABLES

u4byte qt_gen = 0;
u1byte q_tab[2][256];

#define q(n,x)  q_tab[n][x]

void
gen_qtab(void)
{
  u4byte i;

  for (i = 0; i < 256; ++i)
    {
      q(0, i) = qp(0, (u1byte) i);
      q(1, i) = qp(1, (u1byte) i);
    }
};

#else

#define q(n,x)  qp(n, x)

#endif

#ifdef  M_TABLE

u4byte mt_gen = 0;
u4byte m_tab[4][256];

void
gen_mtab(void)
{
  u4byte i, f01, f5b, fef;

  for (i = 0; i < 256; ++i)
    {
      f01 = q(1, i);
      f5b = ffm_5b(f01);
      fef = ffm_ef(f01);
      m_tab[0][i] = f01 + (f5b << 8) + (fef << 16) + (fef << 24);
      m_tab[2][i] = f5b + (fef << 8) + (f01 << 16) + (fef << 24);

      f01 = q(0, i);
      f5b = ffm_5b(f01);
      fef = ffm_ef(f01);
      m_tab[1][i] = fef + (fef << 8) + (f5b << 16) + (f01 << 24);
      m_tab[3][i] = f5b + (f01 << 8) + (fef << 16) + (f5b << 24);
    }
};

#define mds(n,x)    m_tab[n][x]

#else

#define fm_00   ffm_01
#define fm_10   ffm_5b
#define fm_20   ffm_ef
#define fm_30   ffm_ef
#define q_0(x)  q(1,x)

#define fm_01   ffm_ef
#define fm_11   ffm_ef
#define fm_21   ffm_5b
#define fm_31   ffm_01
#define q_1(x)  q(0,x)

#define fm_02   ffm_5b
#define fm_12   ffm_ef
#define fm_22   ffm_01
#define fm_32   ffm_ef
#define q_2(x)  q(1,x)

#define fm_03   ffm_5b
#define fm_13   ffm_01
#define fm_23   ffm_ef
#define fm_33   ffm_5b
#define q_3(x)  q(0,x)

#define f_0(n,x)    ((u4byte)fm_0##n(x))
#define f_1(n,x)    ((u4byte)fm_1##n(x) << 8)
#define f_2(n,x)    ((u4byte)fm_2##n(x) << 16)
#define f_3(n,x)    ((u4byte)fm_3##n(x) << 24)

#define mds(n,x)    f_0(n,q_##n(x)) ^ f_1(n,q_##n(x)) ^ f_2(n,q_##n(x)) ^ f_3(n,q_##n(x))

#endif

u4byte
h_fun(const u4byte x, const u4byte key[])
{
  u4byte b0, b1, b2, b3;

#ifndef M_TABLE
  u4byte m5b_b0, m5b_b1, m5b_b2, m5b_b3;
  u4byte mef_b0, mef_b1, mef_b2, mef_b3;

#endif

  b0 = byte(x, 0);
  b1 = byte(x, 1);
  b2 = byte(x, 2);
  b3 = byte(x, 3);

  switch (k_len)
    {
    case 4:
      b0 = q(1, b0) ^ byte(key[3], 0);
      b1 = q(0, b1) ^ byte(key[3], 1);
      b2 = q(0, b2) ^ byte(key[3], 2);
      b3 = q(1, b3) ^ byte(key[3], 3);
    case 3:
      b0 = q(1, b0) ^ byte(key[2], 0);
      b1 = q(1, b1) ^ byte(key[2], 1);
      b2 = q(0, b2) ^ byte(key[2], 2);
      b3 = q(0, b3) ^ byte(key[2], 3);
    case 2:
      b0 = q(0, q(0, b0) ^ byte(key[1], 0)) ^ byte(key[0], 0);
      b1 = q(0, q(1, b1) ^ byte(key[1], 1)) ^ byte(key[0], 1);
      b2 = q(1, q(0, b2) ^ byte(key[1], 2)) ^ byte(key[0], 2);
      b3 = q(1, q(1, b3) ^ byte(key[1], 3)) ^ byte(key[0], 3);
    }
#ifdef  M_TABLE

  return mds(0, b0) ^ mds(1, b1) ^ mds(2, b2) ^ mds(3, b3);

#else

  b0 = q(1, b0);
  b1 = q(0, b1);
  b2 = q(1, b2);
  b3 = q(0, b3);
  m5b_b0 = ffm_5b(b0);
  m5b_b1 = ffm_5b(b1);
  m5b_b2 = ffm_5b(b2);
  m5b_b3 = ffm_5b(b3);
  mef_b0 = ffm_ef(b0);
  mef_b1 = ffm_ef(b1);
  mef_b2 = ffm_ef(b2);
  mef_b3 = ffm_ef(b3);
  b0 ^= mef_b1 ^ m5b_b2 ^ m5b_b3;
  b3 ^= m5b_b0 ^ mef_b1 ^ mef_b2;
  b2 ^= mef_b0 ^ m5b_b1 ^ mef_b3;
  b1 ^= mef_b0 ^ mef_b2 ^ m5b_b3;

  return b0 | (b3 << 8) | (b2 << 16) | (b1 << 24);

#endif
};

#ifdef  MK_TABLE

#ifdef  ONE_STEP
u4byte mk_tab[4][256];

#else
u1byte sb[4][256];

#endif

#define q20(x)  q(0,q(0,x) ^ byte(key[1],0)) ^ byte(key[0],0)
#define q21(x)  q(0,q(1,x) ^ byte(key[1],1)) ^ byte(key[0],1)
#define q22(x)  q(1,q(0,x) ^ byte(key[1],2)) ^ byte(key[0],2)
#define q23(x)  q(1,q(1,x) ^ byte(key[1],3)) ^ byte(key[0],3)

#define q30(x)  q(0,q(0,q(1, x) ^ byte(key[2],0)) ^ byte(key[1],0)) ^ byte(key[0],0)
#define q31(x)  q(0,q(1,q(1, x) ^ byte(key[2],1)) ^ byte(key[1],1)) ^ byte(key[0],1)
#define q32(x)  q(1,q(0,q(0, x) ^ byte(key[2],2)) ^ byte(key[1],2)) ^ byte(key[0],2)
#define q33(x)  q(1,q(1,q(0, x) ^ byte(key[2],3)) ^ byte(key[1],3)) ^ byte(key[0],3)

#define q40(x)  q(0,q(0,q(1, q(1, x) ^ byte(key[3],0)) ^ byte(key[2],0)) ^ byte(key[1],0)) ^ byte(key[0],0)
#define q41(x)  q(0,q(1,q(1, q(0, x) ^ byte(key[3],1)) ^ byte(key[2],1)) ^ byte(key[1],1)) ^ byte(key[0],1)
#define q42(x)  q(1,q(0,q(0, q(0, x) ^ byte(key[3],2)) ^ byte(key[2],2)) ^ byte(key[1],2)) ^ byte(key[0],2)
#define q43(x)  q(1,q(1,q(0, q(1, x) ^ byte(key[3],3)) ^ byte(key[2],3)) ^ byte(key[1],3)) ^ byte(key[0],3)

void
gen_mk_tab(u4byte key[])
{
  u4byte i;
  u1byte by;

  switch (k_len)
    {
    case 2:
      for (i = 0; i < 256; ++i)
	{
	  by = (u1byte) i;
#ifdef ONE_STEP
	  mk_tab[0][i] = mds(0, q20(by));
	  mk_tab[1][i] = mds(1, q21(by));
	  mk_tab[2][i] = mds(2, q22(by));
	  mk_tab[3][i] = mds(3, q23(by));
#else
	  sb[0][i] = q20(by);
	  sb[1][i] = q21(by);
	  sb[2][i] = q22(by);
	  sb[3][i] = q23(by);
#endif
	}
      break;

    case 3:
      for (i = 0; i < 256; ++i)
	{
	  by = (u1byte) i;
#ifdef ONE_STEP
	  mk_tab[0][i] = mds(0, q30(by));
	  mk_tab[1][i] = mds(1, q31(by));
	  mk_tab[2][i] = mds(2, q32(by));
	  mk_tab[3][i] = mds(3, q33(by));
#else
	  sb[0][i] = q30(by);
	  sb[1][i] = q31(by);
	  sb[2][i] = q32(by);
	  sb[3][i] = q33(by);
#endif
	}
      break;

    case 4:
      for (i = 0; i < 256; ++i)
	{
	  by = (u1byte) i;
#ifdef ONE_STEP
	  mk_tab[0][i] = mds(0, q40(by));
	  mk_tab[1][i] = mds(1, q41(by));
	  mk_tab[2][i] = mds(2, q42(by));
	  mk_tab[3][i] = mds(3, q43(by));
#else
	  sb[0][i] = q40(by);
	  sb[1][i] = q41(by);
	  sb[2][i] = q42(by);
	  sb[3][i] = q43(by);
#endif
	}
    }
};

#ifdef ONE_STEP
#define g0_fun(x) ( mk_tab[0][byte(x,0)] ^ mk_tab[1][byte(x,1)] \
                      ^ mk_tab[2][byte(x,2)] ^ mk_tab[3][byte(x,3)] )
#define g1_fun(x) ( mk_tab[0][byte(x,3)] ^ mk_tab[1][byte(x,0)] \
                      ^ mk_tab[2][byte(x,1)] ^ mk_tab[3][byte(x,2)] )
#else
#define g0_fun(x) ( mds(0, sb[0][byte(x,0)]) ^ mds(1, sb[1][byte(x,1)]) \
                      ^ mds(2, sb[2][byte(x,2)]) ^ mds(3, sb[3][byte(x,3)]) )
#define g1_fun(x) ( mds(0, sb[0][byte(x,3)]) ^ mds(1, sb[1][byte(x,0)]) \
                      ^ mds(2, sb[2][byte(x,1)]) ^ mds(3, sb[3][byte(x,2)]) )
#endif

#else

#define g0_fun(x)   h_fun(x,s_key)
#define g1_fun(x)   h_fun(rotl(x,8),s_key)

#endif

/* The (12,8) Reed Soloman code has the generator polynomial

   g(x) = x^4 + (a + 1/a) * x^3 + a * x^2 + (a + 1/a) * x + 1

   where the coefficients are in the finite field GF(2^8) with a
   modular polynomial a^8 + a^6 + a^3 + a^2 + 1. To generate the
   remainder we have to start with a 12th order polynomial with our
   eight input bytes as the coefficients of the 4th to 11th terms. 
   That is:

   m[7] * x^11 + m[6] * x^10 ... + m[0] * x^4 + 0 * x^3 +... + 0

   We then multiply the generator polynomial by m[7] * x^7 and subtract
   it - xor in GF(2^8) - from the above to eliminate the x^7 term (the 
   artihmetic on the coefficients is done in GF(2^8). We then multiply 
   the generator polynomial by x^6 * coeff(x^10) and use this to remove
   the x^10 term. We carry on in this way until the x^4 term is removed
   so that we are left with:

   r[3] * x^3 + r[2] * x^2 + r[1] 8 x^1 + r[0]

   which give the resulting 4 bytes of the remainder. This is equivalent 
   to the matrix multiplication in the Twofish description but much faster 
   to implement.

 */

#define G_MOD   0x0000014d

u4byte
mds_rem(u4byte p0, u4byte p1)
{
  u4byte i, t, u;

  for (i = 0; i < 8; ++i)
    {
      t = p1 >> 24;

      p1 = (p1 << 8) | (p0 >> 24);
      p0 <<= 8;

      u = (t << 1);

      if (t & 0x80)

	u ^= G_MOD;

      p1 ^= t ^ (u << 16);

      u ^= (t >> 1);

      if (t & 0x01)

	u ^= G_MOD >> 1;

      p1 ^= (u << 24) | (u << 8);

    }

  return p1;
};

/* initialise the key schedule from the user supplied key   */

u4byte *
twofish_setkey(const u4byte in_key[], const u4byte key_len)
{
  u4byte i, a, b, me_key[4], mo_key[4];

#ifdef Q_TABLES
  if (!qt_gen)
    {
      gen_qtab();
      qt_gen = 1;
    }
#endif

#ifdef M_TABLE
  if (!mt_gen)
    {
      gen_mtab();
      mt_gen = 1;
    }
#endif

  k_len = key_len / 64;		/* 2, 3 or 4 */

  for (i = 0; i < k_len; ++i)
    {
      a = in_key[i + i];
      me_key[i] = a;
      b = in_key[i + i + 1];
      mo_key[i] = b;
      s_key[k_len - i - 1] = mds_rem(a, b);
    }

  for (i = 0; i < 40; i += 2)
    {
      a = 0x01010101 * i;
      b = a + 0x01010101;
      a = h_fun(a, me_key);
      b = rotl(h_fun(b, mo_key), 8);
      l4_key[i] = a + b;
      l4_key[i + 1] = rotl(a + 2 * b, 9);
    }

#ifdef MK_TABLE
  gen_mk_tab(s_key);
#endif

  return l4_key;
};

/* encrypt a block of text  */

#define f_rnd(i)                                                    \
    t1 = g1_fun(blk[1]); t0 = g0_fun(blk[0]);                       \
    blk[2] = rotr(blk[2] ^ (t0 + t1 + l4_key[4 * (i) + 8]), 1);      \
    blk[3] = rotl(blk[3], 1) ^ (t0 + 2 * t1 + l4_key[4 * (i) + 9]);  \
    t1 = g1_fun(blk[3]); t0 = g0_fun(blk[2]);                       \
    blk[0] = rotr(blk[0] ^ (t0 + t1 + l4_key[4 * (i) + 10]), 1);     \
    blk[1] = rotl(blk[1], 1) ^ (t0 + 2 * t1 + l4_key[4 * (i) + 11])

void
twofish_encrypt(const u4byte in_blk[4], u4byte out_blk[])
{
  u4byte t0, t1, blk[4];

  blk[0] = in_blk[0] ^ l4_key[0];
  blk[1] = in_blk[1] ^ l4_key[1];
  blk[2] = in_blk[2] ^ l4_key[2];
  blk[3] = in_blk[3] ^ l4_key[3];

  f_rnd(0);
  f_rnd(1);
  f_rnd(2);
  f_rnd(3);
  f_rnd(4);
  f_rnd(5);
  f_rnd(6);
  f_rnd(7);

  out_blk[0] = blk[2] ^ l4_key[4];
  out_blk[1] = blk[3] ^ l4_key[5];
  out_blk[2] = blk[0] ^ l4_key[6];
  out_blk[3] = blk[1] ^ l4_key[7];
};

/* decrypt a block of text  */

#define i_rnd(i)                                                        \
        t1 = g1_fun(blk[1]); t0 = g0_fun(blk[0]);                       \
        blk[2] = rotl(blk[2], 1) ^ (t0 + t1 + l4_key[4 * (i) + 10]);     \
        blk[3] = rotr(blk[3] ^ (t0 + 2 * t1 + l4_key[4 * (i) + 11]), 1); \
        t1 = g1_fun(blk[3]); t0 = g0_fun(blk[2]);                       \
        blk[0] = rotl(blk[0], 1) ^ (t0 + t1 + l4_key[4 * (i) +  8]);     \
        blk[1] = rotr(blk[1] ^ (t0 + 2 * t1 + l4_key[4 * (i) +  9]), 1)

void
twofish_decrypt(const u4byte in_blk[4], u4byte out_blk[4])
{
  u4byte t0, t1, blk[4];

  blk[0] = in_blk[0] ^ l4_key[4];
  blk[1] = in_blk[1] ^ l4_key[5];
  blk[2] = in_blk[2] ^ l4_key[6];
  blk[3] = in_blk[3] ^ l4_key[7];

  i_rnd(7);
  i_rnd(6);
  i_rnd(5);
  i_rnd(4);
  i_rnd(3);
  i_rnd(2);
  i_rnd(1);
  i_rnd(0);

  out_blk[0] = blk[2] ^ l4_key[0];
  out_blk[1] = blk[3] ^ l4_key[1];
  out_blk[2] = blk[0] ^ l4_key[2];
  out_blk[3] = blk[1] ^ l4_key[3];
};
