static internal void InitPromptstruct(
ref NativeMethods.CRYPTPROTECT_PROMPTSTRUCT ps)
{
ps.cbSize = Marshal.SizeOf(
typeof(NativeMethods.CRYPTPROTECT_PROMPTSTRUCT));
ps.dwPromptFlags = 0;
ps.hwndApp = NativeMethods.NullPtr;
ps.szPrompt = null;
}
internal static byte[] UnprotectData(byte[] data,
int dwFlags)
{
byte[] clearText = null;
// Copy data into unmanaged memory.
NativeMethods.DATA_BLOB din =
new NativeMethods.DATA_BLOB();
din.cbData = data.Length;
din.pbData = Marshal.AllocHGlobal(din.cbData);
Marshal.Copy(data, 0, din.pbData, din.cbData);
NativeMethods.CRYPTPROTECT_PROMPTSTRUCT ps =
new NativeMethods.CRYPTPROTECT_PROMPTSTRUCT();
InitPromptstruct(ref ps);
NativeMethods.DATA_BLOB dout =
new NativeMethods.DATA_BLOB();
try {
bool ret =
NativeMethods.CryptUnprotectData(
ref din,
null,
NativeMethods.NullPtr,
NativeMethods.NullPtr,
ref ps,
dwFlags,
ref dout);
if (ret)
{
clearText = new byte[dout.cbData];
Marshal.Copy(dout.pbData,
clearText, 0, dout.cbData);
NativeMethods.LocalFree(dout.pbData);
}
else
{
#if (DEBUG)
Console.WriteLine("Decryption failed: " +
Marshal.GetLastWin32Error().ToString());
#endif
}
}
finally {
if (din.pbData != IntPtr.Zero)
{
Marshal.FreeHGlobal(din.pbData);
}
}
return(clearText);
}