unsafe public static byte[] CryptProtectString(
string str, string description, uint dwFlags, string promptText)
{
// output buffer
DATA_BLOB dataOut = new DATA_BLOB();
try
{
// prompt struct
CRYPTPROTECT_PROMPTSTRUCT promptStruct = new CRYPTPROTECT_PROMPTSTRUCT();
promptStruct.cbSize = (uint)Marshal.SizeOf(promptStruct);
if (promptText != null)
{
promptStruct.dwPromptFlags = CRYPTPROTECT.PROMPT_ON_PROTECT;
promptStruct.szPrompt = promptText;
}
// pin buffer for encrypt
fixed (char* data = str)
{
// input buffer
DATA_BLOB dataIn = new DATA_BLOB();
dataIn.cbData = (uint)((str.Length + 1) * 2);
dataIn.pbData = new IntPtr(data);
// attempt to encrypt the data
if (!CryptProtectData(
ref dataIn, // data-input
description, // description of data
IntPtr.Zero, // no entropy data
IntPtr.Zero, // reserved
ref promptStruct, // prompt-info
dwFlags, // flags
ref dataOut))
{
throw new Win32Exception(Marshal.GetLastWin32Error(), "Error encryting " + description);
}
}
// return the encrtyped data as a managed byte-array
byte[] encryptedData = new byte[dataOut.cbData];
Marshal.Copy(dataOut.pbData, encryptedData, 0, (int)dataOut.cbData);
return encryptedData;
}
finally
{
if (dataOut.pbData != IntPtr.Zero)
Kernel32.LocalFree(dataOut.pbData);
}
}
unsafe public static string CryptUnprotectString(
byte[] encryptedStr, out string description, uint flags, string promptText)
{
// out variables
IntPtr dataDescription = IntPtr.Zero;
DATA_BLOB dataOut = new DATA_BLOB();
try
{
// prompt struct
CRYPTPROTECT_PROMPTSTRUCT promptStruct = new CRYPTPROTECT_PROMPTSTRUCT();
promptStruct.cbSize = (uint)Marshal.SizeOf(promptStruct);
if (promptText != null)
{
promptStruct.dwPromptFlags = CRYPTPROTECT.PROMPT_ON_UNPROTECT;
promptStruct.szPrompt = promptText;
}
// pin buffer for decryption
fixed (byte* data = encryptedStr)
{
// encrypted data
DATA_BLOB encrtypedData = new DATA_BLOB();
encrtypedData.cbData = (uint)encryptedStr.Length;
encrtypedData.pbData = new IntPtr(data);
// unencrypt
if (!CryptUnprotectData(
ref encrtypedData,
out dataDescription,
IntPtr.Zero,
IntPtr.Zero,
ref promptStruct,
flags,
ref dataOut))
{
throw new Win32Exception(Marshal.GetLastWin32Error(), "Error decrypting data");
}
// return the string
description = Marshal.PtrToStringUni(dataDescription);
return Marshal.PtrToStringUni(dataOut.pbData);
}
}
finally
{
if (dataDescription != IntPtr.Zero)
Kernel32.LocalFree(dataDescription);
if (dataOut.pbData != IntPtr.Zero)
Kernel32.LocalFree(dataOut.pbData);
}
}
public static extern bool CryptUnprotectData(
ref DATA_BLOB pDataIn,
out IntPtr ppszDataDescr,
IntPtr pOptionalEntropy,
IntPtr pvReserved,
ref CRYPTPROTECT_PROMPTSTRUCT pPromptStruct,
uint dwFlags,
ref DATA_BLOB pDataOut
);
public static extern bool CryptProtectData(
ref DATA_BLOB pDataIn,
[MarshalAs(UnmanagedType.LPWStr)] string szDataDescr,
IntPtr pOptionalEntropy,
IntPtr pvReserved,
ref CRYPTPROTECT_PROMPTSTRUCT pPromptStruct,
uint dwFlags,
ref DATA_BLOB pDataOut
);
