encrypto.ex

defmodule Encrypto do
  @encrypto_secret_key System.get_env("ENCRYPTO_SECRET_KEY")
  @encrypto_aad_context System.get_env("ENCRYPTO_AAD_CONTEXT")

  def encrypt(msg) do
    decoded_key = Base.decode16!(@encrypto_secret_key)

    iv = :crypto.strong_rand_bytes(32)

    {ct, tag} = :crypto.block_encrypt(:aes_gcm, decoded_key, iv, {@encrypto_aad_context, msg})

    Base.encode16(iv <> tag <> ct)
  end

  def decrypt(msg) do
    decoded_key = Base.decode16!(@encrypto_secret_key)

    <<iv::binary-32, tag::binary-16, ct::binary>> = Base.decode16!(msg)

    :crypto.block_decrypt(:aes_gcm, decoded_key, iv, {@encrypto_aad_context, ct, tag})
  end
end