Definition gap:list byte -> list int := SHA256.generate_and_pad.

Lemma FOLD_HB_eq: forall l ls, length l = (c + p)%nat -> Forall (fun x => length x = (c + p)%nat) ls -> fold_left h (l :: ls) (Vector.to_list iv_v) = hash_blocks_bits (HMAC_spec_concat.HMAC_Concat.b c p) B h (Vector.to_list iv_v) (l ++ concat ls).