Problem - Kevin Tafuro

}
}
if (hWndParent) EnableWindow(hWndParent, TRUE);
}
if (dEntropy >= cbOutput * 8) {
if (CryptGetHashParam(hHash, HP_HASHVAL, pbHashData, &cbHashData, 0)) {
bResult = TRUE;
CopyMemory(pbOutput, pbHashData, cbOutput);
}
}
done:
if (pbHashData) LocalFree(pbHashData);
if (hHash) CryptDestroyHash(hHash);
if (hProvider) CryptReleaseContext(hProvider, 0);
return bResult;
}
There are other ways to achieve the same result on Windows. For example, you
could install a temporary hook to intercept all messages and use the modal dialog
functions instead of the modeless ones that we have used here. Another possibility is
to be collecting entropy throughout your entire program by installing a more permanent
hook or by moving the entropy collection code out of
SpcGatherKeyboardEntropy( ) and placing it into your program’s main message-processing
loop. SpcGatherKeyboardEntropy( ) could then be modified to operate in global
state, presenting a dialog only if there is not a sufficient amount of entropy
collected already.
Note that the dialog uses a progress bar control. While this control is a standard control
on Windows, it is part of the common controls, so you must initialize common
controls before instantiating the dialog; otherwise, CreateDialog( ) will fail inexplicably
(GetLastError( ) will return 0, which obviously is not very informative). The following
code demonstrates initializing common controls and calling
SpcGatherKeyboardEntropy( ):
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine,
int nShowCmd) {
BYTE pbEntropy[20];
INITCOMMONCONTROLSEX CommonControls;
CommonControls.dwSize = sizeof(CommonControls);
CommonControls.dwICC = ICC_PROGRESS_CLASS;
InitCommonControlsEx(&CommonControls);
SpcGatherKeyboardEntropy(hInstance, 0, pbEntropy, sizeof(pbEntropy));
return 0;
}
See Also
Recipes 4.14, 6.5, 11.19
Gathering Entropy from the Keyboard | 637
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