thing.ex

# DOES NOT WORK
  def sub_word(<< w :: size(32) >>) do
    for <<b <- w>>, into: <<>> do
      << :binary.at(@s_box, b) >>
    end
  end
#  ** (ArgumentError) argument error
#    :erlang.bit_size(1)
#    lib/symmetric/aes.ex:27: Symmetric.AES.sub_word/1


  # WORKS
  def sub_word_alt(<< a, b, c, d >>) do
    <<
    :binary.at(@s_box, a),
    :binary.at(@s_box, b),
    :binary.at(@s_box, c),
    :binary.at(@s_box, d),
    >>
  end