Specified key is not a valid size for this algorithm

Hey,

Sidder og roder med noget kryptering, men jeg får en Exception når jeg forsøger at kryptere noget.

"Specified key is not a valid size for this algorithm" - ja, det siger jo det hele, men hvordan får jeg nøglen til at være en gyldig størrelse?

Min kode:

Private _password As String
        Private _iv As Byte() = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}

        Public Property Password() As String
            Get
                Return _password
            End Get
            Set(ByVal value As String)
                _password = value
            End Set
        End Property

Public Sub Encrypt(ByVal name As String, ByVal data As String)
            Dim loc As String = String.Format("{0}\{1}.txt", Locations.SafeItemsDirectory, name)
            Dim key As Byte() = Encoding.UTF8.GetBytes(_password)

            Dim fStream As FileStream = File.Open(loc, FileMode.OpenOrCreate)

            Dim RijndaelAlg As Rijndael = Rijndael.Create
            RijndaelAlg.Key = key ' Her går det galt
            RijndaelAlg.IV = _iv

            Dim cStream As New CryptoStream(fStream, RijndaelAlg.CreateEncryptor(), CryptoStreamMode.Write)
            Dim sWriter As New StreamWriter(cStream)

            sWriter.WriteLine(data)
            sWriter.Close()
            cStream.Close()
            fStream.Close()
        End Sub