encrypted_field.ex

defmodule MyApp.EncryptedField do
  @behaviour Ecto.Type

  def type, do: :binary

  def cast(value) do
    {:ok, to_string(value)}
  end

  # This is called when the field value is about to be written to the database
  def dump(value) do
    ciphertext = value |> to_string |> MyApp.EncryptionTool.encrypt
    {:ok, ciphertext}
  end

  # This is called when the field is loaded from the database
  def load(value) do
    {:ok, MyApp.EncryptionTool.decrypt(value)}
  end
end