/*
* GOST 28147-89
* (C) 1999-2009 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#include <botan/gost_28147.h>
#include <botan/loadstor.h>
#include <botan/rotate.h>

namespace Botan {

byte GOST_28147_89_Params::sbox_entry(size_t row, size_t col) const
   {
   byte x = sboxes[4 * col + (row / 2)];

   return (row % 2 == 0) ? (x >> 4) : (x & 0x0F);
   }

GOST_28147_89_Params::GOST_28147_89_Params(const std::string& n) : name(n)
   {
   // Encoded in the packed fromat from RFC 4357

   // GostR3411_94_TestParamSet (OID 1.2.643.2.2.31.0)
   static const byte GOST_R_3411_TEST_PARAMS[64] = {
      0x4E, 0x57, 0x64, 0xD1, 0xAB, 0x8D, 0xCB, 0xBF, 0x94, 0x1A, 0x7A,
      0x4D, 0x2C, 0xD1, 0x10, 0x10, 0xD6, 0xA0, 0x57, 0x35, 0x8D, 0x38,
      0xF2, 0xF7, 0x0F, 0x49, 0xD1, 0x5A, 0xEA, 0x2F, 0x8D, 0x94, 0x62,
      0xEE, 0x43, 0x09, 0xB3, 0xF4, 0xA6, 0xA2, 0x18, 0xC6, 0x98, 0xE3,
      0xC1, 0x7C, 0xE5, 0x7E, 0x70, 0x6B, 0x09, 0x66, 0xF7, 0x02, 0x3C,
      0x8B, 0x55, 0x95, 0xBF, 0x28, 0x39, 0xB3, 0x2E, 0xCC };

   // GostR3411-94-CryptoProParamSet (OID 1.2.643.2.2.31.1)
   static const byte GOST_R_3411_CRYPTOPRO_PARAMS[64] = {
      0xA5, 0x74, 0x77, 0xD1, 0x4F, 0xFA, 0x66, 0xE3, 0x54, 0xC7, 0x42,
      0x4A, 0x60, 0xEC, 0xB4, 0x19, 0x82, 0x90, 0x9D, 0x75, 0x1D, 0x4F,
      0xC9, 0x0B, 0x3B, 0x12, 0x2F, 0x54, 0x79, 0x08, 0xA0, 0xAF, 0xD1,
      0x3E, 0x1A, 0x38, 0xC7, 0xB1, 0x81, 0xC6, 0xE6, 0x56, 0x05, 0x87,
      0x03, 0x25, 0xEB, 0xFE, 0x9C, 0x6D, 0xF8, 0x6D, 0x2E, 0xAB, 0xDE,
      0x20, 0xBA, 0x89, 0x3C, 0x92, 0xF8, 0xD3, 0x53, 0xBC };

   if(name == "R3411_94_TestParam")
      sboxes = GOST_R_3411_TEST_PARAMS;
   else if(name == "R3411_CryptoPro")
      sboxes = GOST_R_3411_CRYPTOPRO_PARAMS;
   else
      throw Invalid_Argument("GOST_28147_89_Params: Unknown " + name);
   }

/*
* GOST Constructor
*/
GOST_28147_89::GOST_28147_89(const GOST_28147_89_Params& param) :
   BlockCipher(8, 32), SBOX(1024), EK(8)
   {
   // Convert the parallel 4x4 sboxes into larger word-based sboxes
   for(size_t i = 0; i != 4; ++i)
      for(size_t j = 0; j != 256; ++j)
         {
         u32bit T = (param.sbox_entry(2*i  , j % 16)) |
                    (param.sbox_entry(2*i+1, j / 16) << 4);
         SBOX[256*i+j] = rotate_left(T, (11+8*i) % 32);
         }
   }

/*
* Two rounds of GOST
*/
#define GOST_2ROUND(N1, N2, R1, R2)   \
   do {                               \
   u32bit T0 = N1 + EK[R1];           \
   N2 ^= SBOX[get_byte(3, T0)] |      \
         SBOX[get_byte(2, T0)+256] |  \
         SBOX[get_byte(1, T0)+512] |  \
         SBOX[get_byte(0, T0)+768];   \
                                      \
   u32bit T1 = N2 + EK[R2];           \
   N1 ^= SBOX[get_byte(3, T1)] |      \
         SBOX[get_byte(2, T1)+256] |  \
         SBOX[get_byte(1, T1)+512] |  \
         SBOX[get_byte(0, T1)+768];   \
   } while(0)

/*
* GOST Encryption
*/
void GOST_28147_89::encrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   for(size_t i = 0; i != blocks; ++i)
      {
      u32bit N1 = load_le<u32bit>(in, 0);
      u32bit N2 = load_le<u32bit>(in, 1);

      for(size_t j = 0; j != 3; ++j)
         {
         GOST_2ROUND(N1, N2, 0, 1);
         GOST_2ROUND(N1, N2, 2, 3);
         GOST_2ROUND(N1, N2, 4, 5);
         GOST_2ROUND(N1, N2, 6, 7);
         }

      GOST_2ROUND(N1, N2, 7, 6);
      GOST_2ROUND(N1, N2, 5, 4);
      GOST_2ROUND(N1, N2, 3, 2);
      GOST_2ROUND(N1, N2, 1, 0);

      store_le(out, N2, N1);

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

/*
* GOST Decryption
*/
void GOST_28147_89::decrypt_n(const byte in[], byte out[], size_t blocks) const
   {
   for(size_t i = 0; i != blocks; ++i)
      {
      u32bit N1 = load_le<u32bit>(in, 0);
      u32bit N2 = load_le<u32bit>(in, 1);

      GOST_2ROUND(N1, N2, 0, 1);
      GOST_2ROUND(N1, N2, 2, 3);
      GOST_2ROUND(N1, N2, 4, 5);
      GOST_2ROUND(N1, N2, 6, 7);

      for(size_t j = 0; j != 3; ++j)
         {
         GOST_2ROUND(N1, N2, 7, 6);
         GOST_2ROUND(N1, N2, 5, 4);
         GOST_2ROUND(N1, N2, 3, 2);
         GOST_2ROUND(N1, N2, 1, 0);
         }

      store_le(out, N2, N1);
      in += BLOCK_SIZE;
      out += BLOCK_SIZE;
      }
   }

/*
* GOST Key Schedule
*/
void GOST_28147_89::key_schedule(const byte key[], size_t)
   {
   for(size_t i = 0; i != 8; ++i)
      EK[i] = load_le<u32bit>(key, i);
   }

}