Lemma HMAC_DRBG_generate_helper_Z_Zlength_snd:
forall HMAC key v z,
0 <= z ->
(forall x y, Zlength (HMAC x y) = 32) ->
(exists n, z = n * 32) ->
Zlength (snd (HMAC_DRBG_generate_helper_Z HMAC key v z)) = z.