C / C++ / MFC

Brandon T. H. wrote:

I mean other anti viruses can do that, I wonder how they can though...

szTextChar = szDomainName[ (i % wcslen(szDomainName)) ];
szKeyChar = pzApplicationName[ (i % wcslen(szDomainName)) ];

Private Const VALID_CHARACTERS = "0123456789ABCDEFGHJKLMNPQRSTUVWXYZ"
Private Const DEFAULT_FORMAT = "&&&&-&&&&-&&&&-&&&&"

For i = 1 To CountAmpersands(sFormat)
L1  strTextChar = Mid(strDomainName, (i Mod Len(strDomainName)) + 1, 1)
L2  strKeyChar = Mid(ApplicationName, (i Mod Len(ApplicationName)) + 1, 1)
L3  intTemp = (((Asc(strKeyChar) * i) * Len(ApplicationName) + 1) Mod Len(ValidCharacters) + 1) 'vb returns &H10 which is 16
L4  strTextChar = Chr(Asc(strTextChar) Xor intTemp)
L5  intTemp = (((Asc(strKeyChar) * i) * Len(DomainName) + 1) Mod Len(ValidCharacters) + 1)
L6  strTextChar = Chr(Asc(strTextChar) Xor intTemp)
L7  intEncryptedChar = ((Asc(strTextChar) Xor Asc(strKeyChar)) Mod Len(ValidCharacters)) + 1
L8  strKey = strKey & Mid(ValidCharacters, intEncryptedChar, 1)

   Select Case i
      Case 4, 8, 12
        strKey = strKey & "-"
      End Select

Next i

for (int i = 1; i <= iCount; ++i) {
L1 szTextCharA = szDomainNameA[ ( i % strlen( szDomainNameA )) ];  // Correct
L2 szKeyCharA = szAppKeyA[ ( i % strlen( szAppKeyA )) ];   // Correct
L3 iTemp = ((szKeyCharA * i) * strlen(szAppKeyA)) % strlen( LICENSEKEY_CHARACTERS );//iTemp 16 or &H10
L4 szTextCharA = (char) ((int)szTextCharA ^ iTemp );   // iTemp should be 16 or &H10
L5 iTemp = (int)(szKeyCharA * i) * strlen(szDomainNameA) % strlen( LICENSEKEY_CHARACTERS );
L6 szTextCharA = (char)((int)szTextCharA ^ iTemp);
L7 iEncryptedChar = (int)szTextCharA ^ (int)szKeyCharA % strlen(LICENSEKEY_CHARACTERS);

   // Build up the License Key till it's done.
   if ( i == 1) {
      strncpy_s( szKeyA, iKeyA, &LICENSEKEY_CHARACTERS[ iEncryptedChar ], 1 );
   }
   else {
      strncat_s( szKeyA, iKeyA, &LICENSEKEY_CHARACTERS[ iEncryptedChar ], 1 );
   }

}   // End of for loop

	const char LICENSEKEY_CHARACTERS [] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
	const char LICENSEKEY_FORMAT [] = "&&&&-&&&&-&&&&-&&&&";

WCHAR* CA_LicenseKey::_makeKey( WCHAR *pzAppKeyW, WCHAR *pzDomainNameW )
{
	INT iTemp;
	int iEncryptedChar;	
	char szTextCharA;
	char szKeyCharA;
	char *szKeyA = NULL;
	
	if ( wcslen(pzDomainNameW ) == 0) {
		DWORD dwKey = wcslen( L"Invalid Domain Name" );
		WCHAR *szReturnW = new WCHAR[dwKey+1];
		wcsncpy_s(szReturnW, dwKey+1, L"Invalid Domain Name", dwKey );
		return szReturnW;
	}

	int iDomainNameA = (WideCharToMultiByte(CP_UTF8, 0, (pzDomainNameW), -1, NULL, 0, NULL, NULL) - 1) + 1;	
	char *szDomainNameA = new char[iDomainNameA];
	WideCharToMultiByte(CP_UTF8, 0, pzDomainNameW, -1, szDomainNameA, iDomainNameA, NULL, NULL);
	_strlwr_s( szDomainNameA, iDomainNameA );
	
	int iAppKeyA = (WideCharToMultiByte(CP_UTF8, 0, pzAppKeyW, -1, NULL, 0, NULL, NULL) - 1) + 1;	
	char *szAppKeyA = new char[iDomainNameA];
	WideCharToMultiByte(CP_UTF8, 0, pzAppKeyW, -1, szAppKeyA, iAppKeyA, NULL, NULL);
		
	int iCount = _countAmpersands();
	int iKeyA = strlen(LICENSEKEY_FORMAT)+1;
	szKeyA = new char[ iKeyA+1 ];	
		
	for (int i = 1; i <= iCount; ++i) {				
		
		szTextCharA = szDomainNameA[ ( i % strlen( szDomainNameA )) ];	// Correct
		szKeyCharA = szAppKeyA[ ( i % strlen( szAppKeyA )) ];	// Correct
		
		iTemp = ((szKeyCharA * i) * strlen(szAppKeyA)) % strlen( LICENSEKEY_CHARACTERS ); // iTemp should be 16 or &H10	
		szTextCharA = (char) ((int)szTextCharA ^ iTemp );	// iTemp should be 16 or &H10
		
		iTemp = (int)(szKeyCharA * i) * strlen(szDomainNameA) % strlen( LICENSEKEY_CHARACTERS );
		szTextCharA = (char)((int)szTextCharA ^ iTemp);
		iEncryptedChar = (int)szTextCharA ^ (int)szKeyCharA % strlen(LICENSEKEY_CHARACTERS);
		
		// Build up the License Key till it's done.
		if ( i == 1) {
			strncpy_s( szKeyA, iKeyA, &LICENSEKEY_CHARACTERS[ iEncryptedChar ], 1 );
		}
		else {
			strncat_s( szKeyA, iKeyA, &LICENSEKEY_CHARACTERS[ iEncryptedChar ], 1 );
		}
		
	}	// End of for loop

	delete [] szDomainNameA;
	delete [] szAppKeyA;
	
	WCHAR *szKeyW = NULL;
	return szKeyW;
}

int CA_LicenseKey::_countAmpersands( void )
{
	INT iCount = 0;
	int iLength = 0;
	char *szFormatA = NULL;
	
	iLength = strlen(LICENSEKEY_FORMAT);
	szFormatA = new char[iLength+1];
	strncpy_s( szFormatA, iLength+1, LICENSEKEY_FORMAT, iLength );
	
	for (int i = 0; i <= iLength; ++i) {				
		if ( strncmp( &szFormatA[i], "&", 1) == 0 ) {
			++iCount;
		}		
	}

	delete szFormatA;
	return iCount;
}

strTextChar = static_cast<wchar_t>(static_cast<int>(strTextChar[0]) ^ intTemp);

wcsncmp( &szFormat[i], L"&", 1 ) == 0

if (szFormat [i] == L'&')

for (int i = 0; i <= dwLength; ++i) {
    if (wcsncmp(&szFormat [i], L"&", 1) ==0) {
        ++dwCount;
    }
}