/**
 * Author......: See docs/credits.txt
 * License.....: MIT
 */

#include "inc_vendor.h"
#include "inc_types.h"
#include "inc_platform.h"
#include "inc_common.h"
#include "inc_cipher_aes.h"
#include "inc_cipher_serpent.h"
#include "inc_cipher_twofish.h"
#include "inc_truecrypt_crc32.h"
#include "inc_truecrypt_xts.h"

DECLSPEC void xts_mul2 (PRIVATE_AS u32 *in, PRIVATE_AS u32 *out)
{
  const u32 c = in[3] >> 31;

  out[3] = (in[3] << 1) | (in[2] >> 31);
  out[2] = (in[2] << 1) | (in[1] >> 31);
  out[1] = (in[1] << 1) | (in[0] >> 31);
  out[0] = (in[0] << 1);

  out[0] ^= c * 0x87;
}

DECLSPEC void aes256_decrypt_xts_first (PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2, PRIVATE_AS const u32 *in, PRIVATE_AS u32 *out, PRIVATE_AS u32 *S, PRIVATE_AS u32 *T, PRIVATE_AS u32 *ks, SHM_TYPE u32 *s_te0, SHM_TYPE u32 *s_te1, SHM_TYPE u32 *s_te2, SHM_TYPE u32 *s_te3, SHM_TYPE u32 *s_te4, SHM_TYPE u32 *s_td0, SHM_TYPE u32 *s_td1, SHM_TYPE u32 *s_td2, SHM_TYPE u32 *s_td3, SHM_TYPE u32 *s_td4)
{
  out[0] = in[0];
  out[1] = in[1];
  out[2] = in[2];
  out[3] = in[3];

  aes256_set_encrypt_key (ks, ukey2, s_te0, s_te1, s_te2, s_te3);
  aes256_encrypt (ks, S, T, s_te0, s_te1, s_te2, s_te3, s_te4);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];

  aes256_set_decrypt_key (ks, ukey1, s_te0, s_te1, s_te2, s_te3, s_td0, s_td1, s_td2, s_td3);
  aes256_decrypt (ks, out, out, s_td0, s_td1, s_td2, s_td3, s_td4);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];
}

DECLSPEC void aes256_decrypt_xts_next (PRIVATE_AS const u32 *in, PRIVATE_AS u32 *out, PRIVATE_AS u32 *T, PRIVATE_AS u32 *ks, SHM_TYPE u32 *s_td0, SHM_TYPE u32 *s_td1, SHM_TYPE u32 *s_td2, SHM_TYPE u32 *s_td3, SHM_TYPE u32 *s_td4)
{
  out[0] = in[0];
  out[1] = in[1];
  out[2] = in[2];
  out[3] = in[3];

  xts_mul2 (T, T);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];

  aes256_decrypt (ks, out, out, s_td0, s_td1, s_td2, s_td3, s_td4);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];
}

DECLSPEC void serpent256_decrypt_xts_first (PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2, PRIVATE_AS const u32 *in, PRIVATE_AS u32 *out, PRIVATE_AS u32 *S, PRIVATE_AS u32 *T, PRIVATE_AS u32 *ks)
{
  out[0] = in[0];
  out[1] = in[1];
  out[2] = in[2];
  out[3] = in[3];

  serpent256_set_key (ks, ukey2);
  serpent256_encrypt (ks, S, T);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];

  serpent256_set_key (ks, ukey1);
  serpent256_decrypt (ks, out, out);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];
}

DECLSPEC void serpent256_decrypt_xts_next (PRIVATE_AS const u32 *in, PRIVATE_AS u32 *out, PRIVATE_AS u32 *T, PRIVATE_AS u32 *ks)
{
  out[0] = in[0];
  out[1] = in[1];
  out[2] = in[2];
  out[3] = in[3];

  xts_mul2 (T, T);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];

  serpent256_decrypt (ks, out, out);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];
}

DECLSPEC void twofish256_decrypt_xts_first (PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2, PRIVATE_AS const u32 *in, PRIVATE_AS u32 *out, PRIVATE_AS u32 *S, PRIVATE_AS u32 *T, PRIVATE_AS u32 *sk, PRIVATE_AS u32 *lk)
{
  out[0] = in[0];
  out[1] = in[1];
  out[2] = in[2];
  out[3] = in[3];

  twofish256_set_key (sk, lk, ukey2);
  twofish256_encrypt (sk, lk, S, T);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];

  twofish256_set_key (sk, lk, ukey1);
  twofish256_decrypt (sk, lk, out, out);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];
}

DECLSPEC void twofish256_decrypt_xts_next (PRIVATE_AS const u32 *in, PRIVATE_AS u32 *out, PRIVATE_AS u32 *T, PRIVATE_AS u32 *sk, PRIVATE_AS u32 *lk)
{
  out[0] = in[0];
  out[1] = in[1];
  out[2] = in[2];
  out[3] = in[3];

  xts_mul2 (T, T);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];

  twofish256_decrypt (sk, lk, out, out);

  out[0] ^= T[0];
  out[1] ^= T[1];
  out[2] ^= T[2];
  out[3] ^= T[3];
}

// 512 bit

DECLSPEC int verify_header_aes (GLOBAL_AS const u32 *data_buf, const u32 signature, PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2, SHM_TYPE u32 *s_te0, SHM_TYPE u32 *s_te1, SHM_TYPE u32 *s_te2, SHM_TYPE u32 *s_te3, SHM_TYPE u32 *s_te4, SHM_TYPE u32 *s_td0, SHM_TYPE u32 *s_td1, SHM_TYPE u32 *s_td2, SHM_TYPE u32 *s_td3, SHM_TYPE u32 *s_td4)
{
  u32 ks_aes[60];

  u32 S[4] = { 0 };

  u32 T_aes[4] = { 0 };

  u32 data[4];

  data[0] = data_buf[0];
  data[1] = data_buf[1];
  data[2] = data_buf[2];
  data[3] = data_buf[3];

  u32 tmp[4];

  aes256_decrypt_xts_first (ukey1, ukey2, data, tmp, S, T_aes, ks_aes, s_te0, s_te1, s_te2, s_te3, s_te4, s_td0, s_td1, s_td2, s_td3, s_td4);

  if (tmp[0] != signature) return 0;

  const u32 crc32_save = hc_swap32_S (~tmp[2]);

  // seek to byte 256

  for (int i = 4; i < 64 - 16; i += 4)
  {
    xts_mul2 (T_aes, T_aes);
  }

  // calculate crc32 from here

  u32 crc32 = ~0;

  for (int i = 64 - 16; i < 128 - 16; i += 4)
  {
    data[0] = data_buf[i + 0];
    data[1] = data_buf[i + 1];
    data[2] = data_buf[i + 2];
    data[3] = data_buf[i + 3];

    aes256_decrypt_xts_next (data, tmp, T_aes, ks_aes, s_td0, s_td1, s_td2, s_td3, s_td4);

    crc32 = round_crc32_4 (tmp[0], crc32);
    crc32 = round_crc32_4 (tmp[1], crc32);
    crc32 = round_crc32_4 (tmp[2], crc32);
    crc32 = round_crc32_4 (tmp[3], crc32);
  }

  if (crc32 != crc32_save) return 0;

  return 1;
}

DECLSPEC int verify_header_serpent (GLOBAL_AS const u32 *data_buf, const u32 signature, PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2)
{
  u32 ks_serpent[140];

  u32 S[4] = { 0 };

  u32 T_serpent[4] = { 0 };

  u32 data[4];

  data[0] = data_buf[0];
  data[1] = data_buf[1];
  data[2] = data_buf[2];
  data[3] = data_buf[3];

  u32 tmp[4];

  serpent256_decrypt_xts_first (ukey1, ukey2, data, tmp, S, T_serpent, ks_serpent);

  if (tmp[0] != signature) return 0;

  const u32 crc32_save = hc_swap32_S (~tmp[2]);

  // seek to byte 256

  for (int i = 4; i < 64 - 16; i += 4)
  {
    xts_mul2 (T_serpent, T_serpent);
  }

  // calculate crc32 from here

  u32 crc32 = ~0;

  for (int i = 64 - 16; i < 128 - 16; i += 4)
  {
    data[0] = data_buf[i + 0];
    data[1] = data_buf[i + 1];
    data[2] = data_buf[i + 2];
    data[3] = data_buf[i + 3];

    serpent256_decrypt_xts_next (data, tmp, T_serpent, ks_serpent);

    crc32 = round_crc32_4 (tmp[0], crc32);
    crc32 = round_crc32_4 (tmp[1], crc32);
    crc32 = round_crc32_4 (tmp[2], crc32);
    crc32 = round_crc32_4 (tmp[3], crc32);
  }

  if (crc32 != crc32_save) return 0;

  return 1;
}

DECLSPEC int verify_header_twofish (GLOBAL_AS const u32 *data_buf, const u32 signature, PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2)
{
  u32 sk_twofish[4];
  u32 lk_twofish[40];

  u32 S[4] = { 0 };

  u32 T_twofish[4] = { 0 };

  u32 data[4];

  data[0] = data_buf[0];
  data[1] = data_buf[1];
  data[2] = data_buf[2];
  data[3] = data_buf[3];

  u32 tmp[4];

  twofish256_decrypt_xts_first (ukey1, ukey2, data, tmp, S, T_twofish, sk_twofish, lk_twofish);

  if (tmp[0] != signature) return 0;

  const u32 crc32_save = hc_swap32_S (~tmp[2]);

  // seek to byte 256

  for (int i = 4; i < 64 - 16; i += 4)
  {
    xts_mul2 (T_twofish, T_twofish);
  }

  // calculate crc32 from here

  u32 crc32 = ~0;

  for (int i = 64 - 16; i < 128 - 16; i += 4)
  {
    data[0] = data_buf[i + 0];
    data[1] = data_buf[i + 1];
    data[2] = data_buf[i + 2];
    data[3] = data_buf[i + 3];

    twofish256_decrypt_xts_next (data, tmp, T_twofish, sk_twofish, lk_twofish);

    crc32 = round_crc32_4 (tmp[0], crc32);
    crc32 = round_crc32_4 (tmp[1], crc32);
    crc32 = round_crc32_4 (tmp[2], crc32);
    crc32 = round_crc32_4 (tmp[3], crc32);
  }

  if (crc32 != crc32_save) return 0;

  return 1;
}

// 1024 bit

DECLSPEC int verify_header_aes_twofish (GLOBAL_AS const u32 *data_buf, const u32 signature, PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2, PRIVATE_AS const u32 *ukey3, PRIVATE_AS const u32 *ukey4, SHM_TYPE u32 *s_te0, SHM_TYPE u32 *s_te1, SHM_TYPE u32 *s_te2, SHM_TYPE u32 *s_te3, SHM_TYPE u32 *s_te4, SHM_TYPE u32 *s_td0, SHM_TYPE u32 *s_td1, SHM_TYPE u32 *s_td2, SHM_TYPE u32 *s_td3, SHM_TYPE u32 *s_td4)
{
  u32 ks_aes[60];

  u32 sk_twofish[4];
  u32 lk_twofish[40];

  u32 S[4] = { 0 };

  u32 T_aes[4]     = { 0 };
  u32 T_twofish[4] = { 0 };

  u32 data[4];

  data[0] = data_buf[0];
  data[1] = data_buf[1];
  data[2] = data_buf[2];
  data[3] = data_buf[3];

  u32 tmp[4];

  aes256_decrypt_xts_first     (ukey2, ukey4, data, tmp, S, T_aes,     ks_aes, s_te0, s_te1, s_te2, s_te3, s_te4, s_td0, s_td1, s_td2, s_td3, s_td4);
  twofish256_decrypt_xts_first (ukey1, ukey3, tmp,  tmp, S, T_twofish, sk_twofish, lk_twofish);

  if (tmp[0] != signature) return 0;

  const u32 crc32_save = hc_swap32_S (~tmp[2]);

  // seek to byte 256

  for (int i = 4; i < 64 - 16; i += 4)
  {
    xts_mul2 (T_aes,     T_aes);
    xts_mul2 (T_twofish, T_twofish);
  }

  // calculate crc32 from here

  u32 crc32 = ~0;

  for (int i = 64 - 16; i < 128 - 16; i += 4)
  {
    data[0] = data_buf[i + 0];
    data[1] = data_buf[i + 1];
    data[2] = data_buf[i + 2];
    data[3] = data_buf[i + 3];

    aes256_decrypt_xts_next     (data, tmp, T_aes,     ks_aes, s_td0, s_td1, s_td2, s_td3, s_td4);
    twofish256_decrypt_xts_next (tmp,  tmp, T_twofish, sk_twofish, lk_twofish);

    crc32 = round_crc32_4 (tmp[0], crc32);
    crc32 = round_crc32_4 (tmp[1], crc32);
    crc32 = round_crc32_4 (tmp[2], crc32);
    crc32 = round_crc32_4 (tmp[3], crc32);
  }

  if (crc32 != crc32_save) return 0;

  return 1;
}

DECLSPEC int verify_header_serpent_aes (GLOBAL_AS const u32 *data_buf, const u32 signature, PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2, PRIVATE_AS const u32 *ukey3, PRIVATE_AS const u32 *ukey4, SHM_TYPE u32 *s_te0, SHM_TYPE u32 *s_te1, SHM_TYPE u32 *s_te2, SHM_TYPE u32 *s_te3, SHM_TYPE u32 *s_te4, SHM_TYPE u32 *s_td0, SHM_TYPE u32 *s_td1, SHM_TYPE u32 *s_td2, SHM_TYPE u32 *s_td3, SHM_TYPE u32 *s_td4)
{
  u32 ks_serpent[140];
  u32 ks_aes[60];

  u32 S[4] = { 0 };

  u32 T_serpent[4] = { 0 };
  u32 T_aes[4]     = { 0 };

  u32 data[4];

  data[0] = data_buf[0];
  data[1] = data_buf[1];
  data[2] = data_buf[2];
  data[3] = data_buf[3];

  u32 tmp[4];

  serpent256_decrypt_xts_first (ukey2, ukey4, data, tmp, S, T_serpent, ks_serpent);
  aes256_decrypt_xts_first     (ukey1, ukey3, tmp,  tmp, S, T_aes,     ks_aes, s_te0, s_te1, s_te2, s_te3, s_te4, s_td0, s_td1, s_td2, s_td3, s_td4);

  if (tmp[0] != signature) return 0;

  const u32 crc32_save = hc_swap32_S (~tmp[2]);

  // seek to byte 256

  for (int i = 4; i < 64 - 16; i += 4)
  {
    xts_mul2 (T_serpent, T_serpent);
    xts_mul2 (T_aes,     T_aes);
  }

  // calculate crc32 from here

  u32 crc32 = ~0;

  for (int i = 64 - 16; i < 128 - 16; i += 4)
  {
    data[0] = data_buf[i + 0];
    data[1] = data_buf[i + 1];
    data[2] = data_buf[i + 2];
    data[3] = data_buf[i + 3];

    serpent256_decrypt_xts_next (data, tmp, T_serpent, ks_serpent);
    aes256_decrypt_xts_next     (tmp,  tmp, T_aes,     ks_aes, s_td0, s_td1, s_td2, s_td3, s_td4);

    crc32 = round_crc32_4 (tmp[0], crc32);
    crc32 = round_crc32_4 (tmp[1], crc32);
    crc32 = round_crc32_4 (tmp[2], crc32);
    crc32 = round_crc32_4 (tmp[3], crc32);
  }

  if (crc32 != crc32_save) return 0;

  return 1;
}

DECLSPEC int verify_header_twofish_serpent (GLOBAL_AS const u32 *data_buf, const u32 signature, PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2, PRIVATE_AS const u32 *ukey3, PRIVATE_AS const u32 *ukey4)
{
  u32 sk_twofish[4];
  u32 lk_twofish[40];

  u32 ks_serpent[140];

  u32 S[4] = { 0 };

  u32 T_twofish[4] = { 0 };
  u32 T_serpent[4] = { 0 };

  u32 data[4];

  data[0] = data_buf[0];
  data[1] = data_buf[1];
  data[2] = data_buf[2];
  data[3] = data_buf[3];

  u32 tmp[4];

  twofish256_decrypt_xts_first (ukey2, ukey4, data, tmp, S, T_twofish, sk_twofish, lk_twofish);
  serpent256_decrypt_xts_first (ukey1, ukey3, tmp,  tmp, S, T_serpent, ks_serpent);

  if (tmp[0] != signature) return 0;

  const u32 crc32_save = hc_swap32_S (~tmp[2]);

  // seek to byte 256

  for (int i = 4; i < 64 - 16; i += 4)
  {
    xts_mul2 (T_twofish, T_twofish);
    xts_mul2 (T_serpent, T_serpent);
  }

  // calculate crc32 from here

  u32 crc32 = ~0;

  for (int i = 64 - 16; i < 128 - 16; i += 4)
  {
    data[0] = data_buf[i + 0];
    data[1] = data_buf[i + 1];
    data[2] = data_buf[i + 2];
    data[3] = data_buf[i + 3];

    twofish256_decrypt_xts_next (data, tmp, T_twofish, sk_twofish, lk_twofish);
    serpent256_decrypt_xts_next (tmp,  tmp, T_serpent, ks_serpent);

    crc32 = round_crc32_4 (tmp[0], crc32);
    crc32 = round_crc32_4 (tmp[1], crc32);
    crc32 = round_crc32_4 (tmp[2], crc32);
    crc32 = round_crc32_4 (tmp[3], crc32);
  }

  if (crc32 != crc32_save) return 0;

  return 1;
}

// 1536 bit

DECLSPEC int verify_header_aes_twofish_serpent (GLOBAL_AS const u32 *data_buf, const u32 signature, PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2, PRIVATE_AS const u32 *ukey3, PRIVATE_AS const u32 *ukey4, PRIVATE_AS const u32 *ukey5, PRIVATE_AS const u32 *ukey6, SHM_TYPE u32 *s_te0, SHM_TYPE u32 *s_te1, SHM_TYPE u32 *s_te2, SHM_TYPE u32 *s_te3, SHM_TYPE u32 *s_te4, SHM_TYPE u32 *s_td0, SHM_TYPE u32 *s_td1, SHM_TYPE u32 *s_td2, SHM_TYPE u32 *s_td3, SHM_TYPE u32 *s_td4)
{
  u32 ks_aes[60];

  u32 sk_twofish[4];
  u32 lk_twofish[40];

  u32 ks_serpent[140];

  u32 S[4] = { 0 };

  u32 T_aes[4]     = { 0 };
  u32 T_twofish[4] = { 0 };
  u32 T_serpent[4] = { 0 };

  u32 data[4];

  data[0] = data_buf[0];
  data[1] = data_buf[1];
  data[2] = data_buf[2];
  data[3] = data_buf[3];

  u32 tmp[4];

  aes256_decrypt_xts_first     (ukey3, ukey6, data, tmp, S, T_aes,     ks_aes, s_te0, s_te1, s_te2, s_te3, s_te4, s_td0, s_td1, s_td2, s_td3, s_td4);
  twofish256_decrypt_xts_first (ukey2, ukey5, tmp,  tmp, S, T_twofish, sk_twofish, lk_twofish);
  serpent256_decrypt_xts_first (ukey1, ukey4, tmp,  tmp, S, T_serpent, ks_serpent);

  if (tmp[0] != signature) return 0;

  const u32 crc32_save = hc_swap32_S (~tmp[2]);

  // seek to byte 256

  for (int i = 4; i < 64 - 16; i += 4)
  {
    xts_mul2 (T_aes,     T_aes);
    xts_mul2 (T_twofish, T_twofish);
    xts_mul2 (T_serpent, T_serpent);
  }

  // calculate crc32 from here

  u32 crc32 = ~0;

  for (int i = 64 - 16; i < 128 - 16; i += 4)
  {
    data[0] = data_buf[i + 0];
    data[1] = data_buf[i + 1];
    data[2] = data_buf[i + 2];
    data[3] = data_buf[i + 3];

    aes256_decrypt_xts_next     (data, tmp, T_aes,     ks_aes, s_td0, s_td1, s_td2, s_td3, s_td4);
    twofish256_decrypt_xts_next (tmp,  tmp, T_twofish, sk_twofish, lk_twofish);
    serpent256_decrypt_xts_next (tmp,  tmp, T_serpent, ks_serpent);

    crc32 = round_crc32_4 (tmp[0], crc32);
    crc32 = round_crc32_4 (tmp[1], crc32);
    crc32 = round_crc32_4 (tmp[2], crc32);
    crc32 = round_crc32_4 (tmp[3], crc32);
  }

  if (crc32 != crc32_save) return 0;

  return 1;
}

DECLSPEC int verify_header_serpent_twofish_aes (GLOBAL_AS const u32 *data_buf, const u32 signature, PRIVATE_AS const u32 *ukey1, PRIVATE_AS const u32 *ukey2, PRIVATE_AS const u32 *ukey3, PRIVATE_AS const u32 *ukey4, PRIVATE_AS const u32 *ukey5, PRIVATE_AS const u32 *ukey6, SHM_TYPE u32 *s_te0, SHM_TYPE u32 *s_te1, SHM_TYPE u32 *s_te2, SHM_TYPE u32 *s_te3, SHM_TYPE u32 *s_te4, SHM_TYPE u32 *s_td0, SHM_TYPE u32 *s_td1, SHM_TYPE u32 *s_td2, SHM_TYPE u32 *s_td3, SHM_TYPE u32 *s_td4)
{
  u32 ks_serpent[140];

  u32 sk_twofish[4];
  u32 lk_twofish[40];

  u32 ks_aes[60];

  u32 S[4] = { 0 };

  u32 T_serpent[4] = { 0 };
  u32 T_twofish[4] = { 0 };
  u32 T_aes[4]     = { 0 };

  u32 data[4];

  data[0] = data_buf[0];
  data[1] = data_buf[1];
  data[2] = data_buf[2];
  data[3] = data_buf[3];

  u32 tmp[4];

  serpent256_decrypt_xts_first (ukey3, ukey6, data, tmp, S, T_serpent, ks_serpent);
  twofish256_decrypt_xts_first (ukey2, ukey5, tmp,  tmp, S, T_twofish, sk_twofish, lk_twofish);
  aes256_decrypt_xts_first     (ukey1, ukey4, tmp,  tmp, S, T_aes,     ks_aes, s_te0, s_te1, s_te2, s_te3, s_te4, s_td0, s_td1, s_td2, s_td3, s_td4);

  if (tmp[0] != signature) return 0;

  const u32 crc32_save = hc_swap32_S (~tmp[2]);

  // seek to byte 256

  for (int i = 4; i < 64 - 16; i += 4)
  {
    xts_mul2 (T_serpent, T_serpent);
    xts_mul2 (T_twofish, T_twofish);
    xts_mul2 (T_aes,     T_aes);
  }

  // calculate crc32 from here

  u32 crc32 = ~0;

  for (int i = 64 - 16; i < 128 - 16; i += 4)
  {
    data[0] = data_buf[i + 0];
    data[1] = data_buf[i + 1];
    data[2] = data_buf[i + 2];
    data[3] = data_buf[i + 3];

    serpent256_decrypt_xts_next (data, tmp, T_serpent, ks_serpent);
    twofish256_decrypt_xts_next (tmp,  tmp, T_twofish, sk_twofish, lk_twofish);
    aes256_decrypt_xts_next     (tmp,  tmp, T_aes,     ks_aes, s_td0, s_td1, s_td2, s_td3, s_td4);

    crc32 = round_crc32_4 (tmp[0], crc32);
    crc32 = round_crc32_4 (tmp[1], crc32);
    crc32 = round_crc32_4 (tmp[2], crc32);
    crc32 = round_crc32_4 (tmp[3], crc32);
  }

  if (crc32 != crc32_save) return 0;

  return 1;
}