Lemma HMAC_DRBG_generate_helper_Z_Zlength_fst: forall HMAC key v z, 0 <= z -> Zlength v = 32 -> (forall x y, Zlength (HMAC x y) = 32) -> Zlength (fst (HMAC_DRBG_generate_helper_Z HMAC key v z)) = 32.