-type cipher() :: aes_cbc | aes_gcm.

-type enc() ::
          #jose_jwe_enc_aes{cipher :: undefined | {cipher(), key_size()},
                            bits :: undefined | pos_integer(),
                            cek_len :: undefined | pos_integer(),
                            iv_len :: undefined | pos_integer(),
                            enc_len :: undefined | pos_integer(),
                            mac_len :: undefined | pos_integer(),
                            tag_len :: undefined | pos_integer(),
                            hmac :: undefined | sha256 | sha384 | sha512}.

-type key_size() :: 128 | 192 | 256.