Definition fulllen (len : Z) :=
  len + 1%Z + (- (len + 9) mod 64).

(* Specifications: *)
Lemma app_left : forall (a b c d : list byte), a ++ b ++ c ++ d = (a ++ b ++ c) ++ d.
Theorem pad_compose_equal : forall (msg : list byte), generate_and_pad' msg = generate_and_pad msg.
Theorem length_equal_pad_length : forall (msg1 : list byte) (msg2 : list byte), Zlength msg1 = Zlength msg2 -> Zlength (generate_and_pad msg1) = Zlength (generate_and_pad msg2).