Public Function Sha256_Base64(ByVal ClearString As String, ByVal base64 As Boolean) As String
        Dim sha256x As SHA256 = SHA256Managed.Create()
        Dim bytes As Byte() = Encoding.UTF8.GetBytes(ClearString)
        Dim hash As Byte() = sha256x.ComputeHash(bytes)
        Dim stringBuilder As New StringBuilder()
        For i As Integer = 0 To hash.Length - 1
            stringBuilder.Append(hash(i).ToString("x2"))
        Next
        If base64 = True Then
            Return Convert.ToBase64String(hash)
        Else
            Return stringBuilder.ToString()
        End If
        Return Nothing
    End Function