CryptProtectData

C# Signature:

[
DllImport("Crypt32.dll",
SetLastError=true,
CharSet=System.Runtime.InteropServices.CharSet.Auto)
]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool CryptProtectData(
    ref DATA_BLOB pDataIn, 
    String szDataDescr, 
    ref DATA_BLOB pOptionalEntropy,
    IntPtr pvReserved, 
    ref CRYPTPROTECT_PROMPTSTRUCT pPromptStruct, 
    CryptProtectFlags dwFlags, 
    ref DATA_BLOB pDataOut
);

VB .NET Signature:

<DllImport("Crypt32.dll", SetLastError:=True, CharSet:=System.Runtime.InteropServices.CharSet.Auto)> _
Private Shared Function CryptProtectData ( _
    ByRef pDataIn As DATA_BLOB, _
    ByVal szDataDescr As String, _
    ByRef pOptionalEntropy As DATA_BLOB, _
    ByVal pvReseved As IntPtr, _
    ByRef pPromptStruct As CRYPTPROTECT_PROMPTSTRUCT, _
    ByVal dwFlags As Integer, _
    ByRef pDataOut As DATA_BLOB _
) As Boolean
End Function