/*
* CAST-256
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#include <botan/cast256.h>
#include <botan/loadstor.h>
#include <botan/rotate.h>

namespace Botan {

namespace {

/*
* CAST-256 Round Type 1
*/
void round1(u32bit& out, u32bit in, u32bit mask, u32bit rot)
   {
   u32bit temp = rotate_left(mask + in, rot);
   out  ^= (CAST_SBOX1[get_byte(0, temp)] ^ CAST_SBOX2[get_byte(1, temp)]) -
            CAST_SBOX3[get_byte(2, temp)] + CAST_SBOX4[get_byte(3, temp)];
   }

/*
* CAST-256 Round Type 2
*/
void round2(u32bit& out, u32bit in, u32bit mask, u32bit rot)
   {
   u32bit temp = rotate_left(mask ^ in, rot);
   out  ^= (CAST_SBOX1[get_byte(0, temp)]  - CAST_SBOX2[get_byte(1, temp)] +
            CAST_SBOX3[get_byte(2, temp)]) ^ CAST_SBOX4[get_byte(3, temp)];
   }

/*
* CAST-256 Round Type 3
*/
void round3(u32bit& out, u32bit in, u32bit mask, u32bit rot)
   {
   u32bit temp = rotate_left(mask - in, rot);
   out  ^= ((CAST_SBOX1[get_byte(0, temp)]  + CAST_SBOX2[get_byte(1, temp)]) ^
             CAST_SBOX3[get_byte(2, temp)]) - CAST_SBOX4[get_byte(3, temp)];
   }

}

/*
* CAST-256 Encryption
*/
void CAST_256::encrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   for(size_t i = 0; i != blocks; ++i)
      {
      u32bit A = load_be<u32bit>(in, 0);
      u32bit B = load_be<u32bit>(in, 1);
      u32bit C = load_be<u32bit>(in, 2);
      u32bit D = load_be<u32bit>(in, 3);

      round1(C, D, MK[ 0], RK[ 0]); round2(B, C, MK[ 1], RK[ 1]);
      round3(A, B, MK[ 2], RK[ 2]); round1(D, A, MK[ 3], RK[ 3]);
      round1(C, D, MK[ 4], RK[ 4]); round2(B, C, MK[ 5], RK[ 5]);
      round3(A, B, MK[ 6], RK[ 6]); round1(D, A, MK[ 7], RK[ 7]);
      round1(C, D, MK[ 8], RK[ 8]); round2(B, C, MK[ 9], RK[ 9]);
      round3(A, B, MK[10], RK[10]); round1(D, A, MK[11], RK[11]);
      round1(C, D, MK[12], RK[12]); round2(B, C, MK[13], RK[13]);
      round3(A, B, MK[14], RK[14]); round1(D, A, MK[15], RK[15]);
      round1(C, D, MK[16], RK[16]); round2(B, C, MK[17], RK[17]);
      round3(A, B, MK[18], RK[18]); round1(D, A, MK[19], RK[19]);
      round1(C, D, MK[20], RK[20]); round2(B, C, MK[21], RK[21]);
      round3(A, B, MK[22], RK[22]); round1(D, A, MK[23], RK[23]);
      round1(D, A, MK[27], RK[27]); round3(A, B, MK[26], RK[26]);
      round2(B, C, MK[25], RK[25]); round1(C, D, MK[24], RK[24]);
      round1(D, A, MK[31], RK[31]); round3(A, B, MK[30], RK[30]);
      round2(B, C, MK[29], RK[29]); round1(C, D, MK[28], RK[28]);
      round1(D, A, MK[35], RK[35]); round3(A, B, MK[34], RK[34]);
      round2(B, C, MK[33], RK[33]); round1(C, D, MK[32], RK[32]);
      round1(D, A, MK[39], RK[39]); round3(A, B, MK[38], RK[38]);
      round2(B, C, MK[37], RK[37]); round1(C, D, MK[36], RK[36]);
      round1(D, A, MK[43], RK[43]); round3(A, B, MK[42], RK[42]);
      round2(B, C, MK[41], RK[41]); round1(C, D, MK[40], RK[40]);
      round1(D, A, MK[47], RK[47]); round3(A, B, MK[46], RK[46]);
      round2(B, C, MK[45], RK[45]); round1(C, D, MK[44], RK[44]);

      store_be(out, A, B, C, D);

      in += BLOCK_SIZE;
      out += BLOCK_SIZE;
      }
   }

/*
* CAST-256 Decryption
*/
void CAST_256::decrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   for(size_t i = 0; i != blocks; ++i)
      {
      u32bit A = load_be<u32bit>(in, 0);
      u32bit B = load_be<u32bit>(in, 1);
      u32bit C = load_be<u32bit>(in, 2);
      u32bit D = load_be<u32bit>(in, 3);

      round1(C, D, MK[44], RK[44]); round2(B, C, MK[45], RK[45]);
      round3(A, B, MK[46], RK[46]); round1(D, A, MK[47], RK[47]);
      round1(C, D, MK[40], RK[40]); round2(B, C, MK[41], RK[41]);
      round3(A, B, MK[42], RK[42]); round1(D, A, MK[43], RK[43]);
      round1(C, D, MK[36], RK[36]); round2(B, C, MK[37], RK[37]);
      round3(A, B, MK[38], RK[38]); round1(D, A, MK[39], RK[39]);
      round1(C, D, MK[32], RK[32]); round2(B, C, MK[33], RK[33]);
      round3(A, B, MK[34], RK[34]); round1(D, A, MK[35], RK[35]);
      round1(C, D, MK[28], RK[28]); round2(B, C, MK[29], RK[29]);
      round3(A, B, MK[30], RK[30]); round1(D, A, MK[31], RK[31]);
      round1(C, D, MK[24], RK[24]); round2(B, C, MK[25], RK[25]);
      round3(A, B, MK[26], RK[26]); round1(D, A, MK[27], RK[27]);
      round1(D, A, MK[23], RK[23]); round3(A, B, MK[22], RK[22]);
      round2(B, C, MK[21], RK[21]); round1(C, D, MK[20], RK[20]);
      round1(D, A, MK[19], RK[19]); round3(A, B, MK[18], RK[18]);
      round2(B, C, MK[17], RK[17]); round1(C, D, MK[16], RK[16]);
      round1(D, A, MK[15], RK[15]); round3(A, B, MK[14], RK[14]);
      round2(B, C, MK[13], RK[13]); round1(C, D, MK[12], RK[12]);
      round1(D, A, MK[11], RK[11]); round3(A, B, MK[10], RK[10]);
      round2(B, C, MK[ 9], RK[ 9]); round1(C, D, MK[ 8], RK[ 8]);
      round1(D, A, MK[ 7], RK[ 7]); round3(A, B, MK[ 6], RK[ 6]);
      round2(B, C, MK[ 5], RK[ 5]); round1(C, D, MK[ 4], RK[ 4]);
      round1(D, A, MK[ 3], RK[ 3]); round3(A, B, MK[ 2], RK[ 2]);
      round2(B, C, MK[ 1], RK[ 1]); round1(C, D, MK[ 0], RK[ 0]);

      store_be(out, A, B, C, D);

      in += BLOCK_SIZE;
      out += BLOCK_SIZE;
      }
   }

/*
* CAST-256 Key Schedule
*/
void CAST_256::key_schedule(const byte key[], size_t length)
   {
   SecureVector<u32bit> K(8);
   for(size_t j = 0; j != length; ++j)
      K[j/4] = (K[j/4] << 8) + key[j];

   u32bit A = K[0], B = K[1], C = K[2], D = K[3],
          E = K[4], F = K[5], G = K[6], H = K[7];

   for(size_t j = 0; j != 48; j += 4)
      {
      round1(G, H, KEY_MASK[4*j+ 0], KEY_ROT[(4*j+ 0) % 32]);
      round2(F, G, KEY_MASK[4*j+ 1], KEY_ROT[(4*j+ 1) % 32]);
      round3(E, F, KEY_MASK[4*j+ 2], KEY_ROT[(4*j+ 2) % 32]);
      round1(D, E, KEY_MASK[4*j+ 3], KEY_ROT[(4*j+ 3) % 32]);
      round2(C, D, KEY_MASK[4*j+ 4], KEY_ROT[(4*j+ 4) % 32]);
      round3(B, C, KEY_MASK[4*j+ 5], KEY_ROT[(4*j+ 5) % 32]);
      round1(A, B, KEY_MASK[4*j+ 6], KEY_ROT[(4*j+ 6) % 32]);
      round2(H, A, KEY_MASK[4*j+ 7], KEY_ROT[(4*j+ 7) % 32]);
      round1(G, H, KEY_MASK[4*j+ 8], KEY_ROT[(4*j+ 8) % 32]);
      round2(F, G, KEY_MASK[4*j+ 9], KEY_ROT[(4*j+ 9) % 32]);
      round3(E, F, KEY_MASK[4*j+10], KEY_ROT[(4*j+10) % 32]);
      round1(D, E, KEY_MASK[4*j+11], KEY_ROT[(4*j+11) % 32]);
      round2(C, D, KEY_MASK[4*j+12], KEY_ROT[(4*j+12) % 32]);
      round3(B, C, KEY_MASK[4*j+13], KEY_ROT[(4*j+13) % 32]);
      round1(A, B, KEY_MASK[4*j+14], KEY_ROT[(4*j+14) % 32]);
      round2(H, A, KEY_MASK[4*j+15], KEY_ROT[(4*j+15) % 32]);

      RK[j  ] = (A % 32);
      RK[j+1] = (C % 32);
      RK[j+2] = (E % 32);
      RK[j+3] = (G % 32);
      MK[j  ] = H;
      MK[j+1] = F;
      MK[j+2] = D;
      MK[j+3] = B;
      }
   }

}
