Get MD5 message digest by elixir-lang.

Crypto.ex

defmodule Crypto do
    def md5(s) do
        list_to_binary(Enum.map(bitstring_to_list(:crypto.md5(s)), fn(x) -> integer_to_binary(x, 16) end))
    end
end

It has an bug, because integer_to_binary/2 will trim the 0 in front of an number, like integer_to_binary(02, 16) -> "2" in this case, the caculated md5 length will be decreased. I write an little sample:

   def md5(s) do 
       :crypto.hash(:md5, s)
          |> bitstring_to_list
          |> Enum.map(&(:io_lib.format("~2.16.0b", [&1]))) 
          |> List.flatten 
          |> list_to_bitstring
   end

A few improvements:

1. As @benjamintanweihao points out, bitstring_to_list and list_to_binary have been removed from Elixir.
2. md5 is a top-level function in Erlang, so you can call it simply as :erlang.md5(s).

defmodule Crypto do
  def md5(data) do
    :erlang.md5(data)
    |> :erlang.bitstring_to_list
    |> Enum.map(&(:io_lib.format("~2.16.0b", [&1])))
    |> List.flatten
    |> :erlang.list_to_bitstring
  end
end

I found a clearer way to encode the bitstring: Base.encode16

defmodule Crypto do
  def md5(data) do
    Base.encode16(:erlang.md5(data), case: :lower)
  end
end

@bheeshmar ótima solução.

@bheeshmar awesome

@bheeshmar you win the internet. thanks for this