EOS Decrypt

#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <Wincrypt.h>

#ifdef _MSC_VER
#pragma warning( push )
 #pragma warning( disable : 4996 )
#endif

#define NBYTE(x) (*((BYTE*)&(x)))

static const BYTE pKey[8] = {0xFF, 0x41, 0x54, 0x73, 0x84, 0x9A, 0xC8, 0xA6};

int nDecryptBlock(HCRYPTKEY hKey, unsigned char* pBuffer)
{
  signed int i = 0;
  int dwCheck;
  int result;
  DWORD dwBlockSize = 8;

  CryptDecrypt(hKey, 0, 1, 0, (BYTE *)pBuffer + i, &dwBlockSize);
  i = 0;
  do
  {
    NBYTE(dwCheck) = *(BYTE *)(i + pBuffer);
    if ((BYTE)dwCheck == 0x7F)
    {
      result = 0;
    }
    else if ((BYTE)dwCheck == 0x80u)
    {
      result = 0xFF;
    }
    else
    {
      dwCheck = (unsigned __int8)dwCheck;
      if ((unsigned __int8)dwCheck >= 0x80u)
        result = dwCheck - 1;
      else
        result = dwCheck + 1;
    }
    *(BYTE *)(i++ + pBuffer) = result;
  }
  while ( i < 8 );
  *(DWORD *)pBuffer ^= 0xA4A7FF88;
  *(DWORD *)(pBuffer + 4) ^= 0xA0447823;

  return result;
}

int _tmain(int argc, _TCHAR* argv[])
{
    if(argc != 3)
    {
      printf("Echo of Soul Files Decryptor\n");
      printf("(c) 2015 / Ekey (h4x0r) / v0.1a\n\n");
      printf("[Usage]\n");
      printf("\tEOSDecryptor <pScrFile> <pDstFile>\n");
      printf("[Examples]\n");
      printf("\tEOSDecryptor EOS.ini EOS.ini.dec\n\n");
      return -1;
    }

    FILE * fi = fopen(argv[1], "rb");
    FILE * fo = fopen(argv[2], "wb");

    if (fi == NULL)
    {
      printf("[ERROR]: Can't open file %s\n", argv[1]);
      return -1;
    }

    if (fo == NULL)
    {
      printf("[ERROR]: Can't write output file %s\n", argv[2]);
      return -1;
    }

    fseek(fi, 0, SEEK_END);
    size_t dwSize = ftell(fi);
    fseek(fi, 0, SEEK_SET);

    dwSize -= 4;
    fseek(fi, 4, SEEK_SET);

    unsigned char *pBuffer = new unsigned char[dwSize];
    memset(pBuffer, 0, dwSize);

    fread((char*)pBuffer, dwSize, 1, fi);

    HCRYPTPROV hCryptProv = 0;
    HCRYPTKEY hKey = 0;
    HCRYPTHASH hHash = 0;

    if (!CryptAcquireContextW(&hCryptProv, L"SBENCRYPTIONKEYCONTAINER10", L"Microsoft Enhanced Cryptographic Provider v1.0", 1u, 0) && GetLastError() == 0x80090016)
        CryptAcquireContextW(&hCryptProv, L"SBENCRYPTIONKEYCONTAINER10", 0, 1u, 8u);

    CryptCreateHash(hCryptProv, 0x8003u, 0, 0, &hHash);
    CryptHashData(hHash, pKey, 8u, 0);
    CryptDeriveKey(hCryptProv, 0x6801u, hHash, 0x800000, &hKey);

    int i = 0;
    int dwBlocks = dwSize >> 3;

    do
    {
       nDecryptBlock(hKey, pBuffer + i);
       i += 8;
       --dwBlocks;
    }
    while (dwBlocks);

    fwrite(pBuffer, dwSize, 1, fo);

    fclose(fi);
    fclose(fo);
    printf("Done!\n");
    return 0;
}