(*Variant of Gen_loop_bvec that uses list byte instead of Bvector 256*)
Fixpoint Gen_loop_Zlist (k : list byte) (v : list byte) (n : nat)
  : list (list byte) * (list byte) :=
  match n with
  | O => (nil, v)
  | S n' =>
    let v' := HMAC256 v k in
    let (bits, v'') := Gen_loop_Zlist k v' n' in
    (List.app bits (List.cons v' List.nil), v'')     
  end.

Lemma Gen_loop_Zlist_ZlengthBlocks k: forall n v blocks u, Gen_loop_Zlist k v n = (blocks,u) -> Zlength blocks = Z.of_nat n.