Elixir implementation of encryption and decryption using erlang's :crypto.block_encrypt and :crypto.block_decrypt

erlang-elixir-aes-crypto.ex

defmodule Crypto.AES do
    @block_size 16
    @secret_key ""

    def encrypt(text) do
        secret_key_hash = make_hash(@secret_key, 16)
        
        text = pad_pkcs7(text, @block_size)
        encrypted_text = :crypto.block_encrypt(:aes_ecb, secret_key_hash, text)
        Base.encode64(encrypted_text)
    end

    def decrypt(ciphertext) do
        secret_key_hash = make_hash(@secret_key, 16)
        {:ok, ciphertext} = Base.decode64(ciphertext)
        decrypted_text = :crypto.block_decrypt(:aes_ecb, secret_key_hash, ciphertext)
        
        unpad_pkcs7(decrypted_text)
    end

    defp pad_pkcs7(message, blocksize) do
        pad = blocksize - rem(byte_size(message), blocksize)
        message <> to_string(List.duplicate(pad, pad))
    end

    defp unpad_pkcs7(data) do
        <<pad>> = binary_part(data, byte_size(data), -1)
        binary_part(data, 0, byte_size(data) - pad)
    end

    defp make_hash(text, length) do
      :crypto.hash(:sha512, text)
        |> Base.encode16
        |> String.downcase
        |> String.slice(0, length)
	end

end