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