Demo for Microsoft's Crypt Library

[Mihai Moga]

In my spare time I have implemented a simple Visual C++ application to show the power of Microsoft Crypt Library. The following functions have been implemented and tested using MD5 checksum and RC4 encryption/decryption:

• BOOL GetChecksumBuff er(ALG_ID nAlgorithm, LPBYTE lpszOutputBuffe r, DWORD& dwOutputLength, LPBYTE lpszInputBuffer , DWORD dwInputLength);
• BOOL GetChecksumStri ng(ALG_ID nAlgorithm, CString& strResult, CString strBuffer);
• BOOL GetChecksumFile (ALG_ID nAlgorithm, CString& strResult, CString strPathName);
• BOOL EncryptBuffer(A LG_ID nAlgorithm, LPBYTE lpszOutputBuffe r, DWORD& dwOutputLength, LPBYTE lpszInputBuffer , DWORD dwInputLength, LPBYTE lpszSecretKey, DWORD dwSecretKey);
• BOOL EncryptFile(ALG _ID nAlgorithm, CString strOutputName, CString strInputName, LPBYTE lpszSecretKey, DWORD dwSecretKey);
• BOOL DecryptBuffer(A LG_ID nAlgorithm, LPBYTE lpszOutputBuffe r, DWORD& dwOutputLength, LPBYTE lpszInputBuffer , DWORD dwInputLength, LPBYTE lpszSecretKey, DWORD dwSecretKey);
• BOOL DecryptFile(ALG _ID nAlgorithm, CString strOutputName, CString strInputName, LPBYTE lpszSecretKey, DWORD dwSecretKey);

The demo application is using the computer's name as secret key for encryption/decryption. Target OS: 32bit Windows 2000, XP, Vista, 7. License: GNU General Public License version 3 (GPLv3).

Here is sample usage of the program

CString strBuffer1 = _T("abc"), strResult1;
VERIFY(GetChecksumString(CALG_MD5, strResult1, strBuffer1));
TRACE(_T("MD5(%s) => %s\n"), strBuffer1, strResult1);

CString strBuffer2 = _T("abc"), strResult2;
VERIFY(GetChecksumFile(CALG_SHA1, strResult2, _T("D:\\AddressBook.csv")));
TRACE(_T("SHA1(%s) => %s\n"), strBuffer2, strResult2);

CString strSecretKey = GetComputerID();
LPBYTE lpszSecretKey = (LPBYTE)(LPCTSTR)strSecretKey;
DWORD dwSecretKey = (strSecretKey.GetLength() + 1) * sizeof(TCHAR);
CString strFilename = _T("D:\\AddressBook.csv");
CString strEncrypt = _T("D:\\AddressBook.rc4");
CString strDecrypt = _T("D:\\AddressBook.txt");
VERIFY(EncryptFile(CALG_RC4, strEncrypt, strFilename, lpszSecretKey, dwSecretKey));
VERIFY(DecryptFile(CALG_RC4, strDecrypt, strEncrypt, lpszSecretKey, dwSecretKey));

[Mihai Moga]

How to read decrypted value from registry:

CString ReadCryptRegistry(HKEY hRoot, CString strPath, CString strName, CString strDefaultValue)
{
    CString strValue = strDefaultValue;
    HKEY hKey = NULL;
    DWORD dwResult = 0;
    DWORD dwType = 0;

    BYTE lpszSecretKey[0x1000] = { 0 };
    _tcscpy_s((LPTSTR) lpszSecretKey, sizeof(lpszSecretKey) / sizeof(TCHAR), GetComputerID());
    DWORD dwSecretKey = (_tcslen((LPTSTR) lpszSecretKey) + 1) * sizeof(TCHAR);

    BYTE lpszDataBuffer[0x1000] = { 0 };
    DWORD dwDataLength = 0x1000;

    BYTE lpszTempBuffer[0x1000] = { 0 };
    DWORD dwTempLength = 0x1000;

    if (RegCreateKeyEx(hRoot, strPath, 0, NULL, REG_OPTION_NON_VOLATILE,
        KEY_QUERY_VALUE | KEY_SET_VALUE, NULL, &hKey, &dwResult) == ERROR_SUCCESS)
    {
        if (RegQueryValueEx(hKey, strName, NULL, &dwType, lpszTempBuffer, &dwTempLength) == ERROR_SUCCESS)
        {
            if (DecryptBuffer(CALG_RC4, lpszDataBuffer, dwDataLength, lpszTempBuffer, dwTempLength, lpszSecretKey, dwSecretKey))
            {
                OutputDebugString(_T("Successfully read decrypted key from registry.\n"));
                strValue = (LPCTSTR) lpszDataBuffer;
            }
        }

        VERIFY(RegCloseKey(hKey) == ERROR_SUCCESS);
    }

    return strValue;
}

How to write encrypted value to registry:

CString WriteCryptRegistry(HKEY hRoot, CString strPath, CString strName, CString strValue)
{
    HKEY hKey = NULL;
    DWORD dwResult = 0;
    DWORD dwType = 0;

    BYTE lpszSecretKey[0x1000] = { 0 };
    _tcscpy_s((LPTSTR) lpszSecretKey, sizeof(lpszSecretKey) / sizeof(TCHAR), GetComputerID());
    DWORD dwSecretKey = (_tcslen((LPTSTR) lpszSecretKey) + 1) * sizeof(TCHAR);

    BYTE lpszDataBuffer[0x1000] = { 0 };
    DWORD dwDataLength = 0x1000;

    BYTE lpszTempBuffer[0x1000] = { 0 };
    DWORD dwTempLength = (strValue.GetLength() + 1) * sizeof(TCHAR);
    ::CopyMemory(lpszTempBuffer, (LPCTSTR) strValue, dwTempLength);

    if (EncryptBuffer(CALG_RC4, lpszDataBuffer, dwDataLength, lpszTempBuffer, dwTempLength, lpszSecretKey, dwSecretKey))
    {
        if (RegCreateKeyEx(hRoot, strPath, 0, NULL, REG_OPTION_NON_VOLATILE,
            KEY_QUERY_VALUE | KEY_SET_VALUE | KEY_CREATE_SUB_KEY, NULL, &hKey, &dwResult) == ERROR_SUCCESS)
        {
            if (RegSetValueEx(hKey, strName, 0, REG_BINARY, lpszDataBuffer, dwDataLength) == ERROR_SUCCESS)
            {
                OutputDebugString(_T("Successfully written encrypted key to registry.\n"));
            }

            VERIFY(RegCloseKey(hKey) == ERROR_SUCCESS);
        }
    }

    return strValue;
}