XorULong -TizzyT

    Public Structure XorULong
        Private Shared Rnd As New Random
        Private ReadOnly Secret As ULong
        Private StoredValue, TokenSum, ValueSum As ULong
        Public Sub New(ByRef Token As ULong)
            Secret = BitConverter.ToUInt64(BitConverter.GetBytes(Rnd.NextDouble), 0)
            Token = BitConverter.ToUInt64(BitConverter.GetBytes(Rnd.NextDouble), 0)
            TokenSum = (Secret Xor Token)
        End Sub
        Public Sub Store(ByRef Token As ULong, ByVal Value As ULong)
            If (Secret Xor Token) = TokenSum Then
                Token = BitConverter.ToUInt64(BitConverter.GetBytes(Rnd.NextDouble), 0)
                TokenSum = (Secret Xor Token)
                ValueSum = (Secret Xor Value)
                StoredValue = (Value Xor Token)
            Else
                Throw New Exception("Token checksum mismatch")
            End If
        End Sub
        Default Public ReadOnly Property Value(ByVal Token As ULong) As UInteger
            Get
                Dim R As ULong = (Token Xor StoredValue)
                If (R Xor Secret) = ValueSum _
                    Then Return R _
                    Else Throw New Exception("Value checksum mismatch")
            End Get
        End Property
    End Structure