I was attempting to use this class however I do not see the ProtectedData class under System.Security.Cryptography. Any reason why!

This is what I have so far ...

 Imports System.Security.Cryptography
 Imports System.text.Encoding
 Imports System

 Public Class Security
 Private Shared arrEntropybyte As Byte() = {1,2,3,4,5,6,7,8,9,0}

   Public Shared Function Encrypt(ByVal stringToEncrypt As String) As String
   Dim arrStringbyte As Byte()
   Dim encryptedDBString As Byte()
   Try
     ' Convert the string to a byte array:
     arrStringbyte = Unicode.GetBytes(stringToEncrypt)
     ' Encrypt string
     encryptedDBString = ProtectedData.Protect(stringToEncrypt, arrEntropybyte, DataProtectionScope.CurrentUser)
   Catch ex As Exception
     Throw ex
   End Try
   End Function
 End Class