Lemma HMAC_DRBG_generate_helper_Z_incremental_snd:
forall HMAC key v z v',
0 <= z ->
v' = fst (HMAC_DRBG_generate_helper_Z HMAC key v (z + 32)) ->
snd (HMAC_DRBG_generate_helper_Z HMAC key v z) ++ v' = snd (HMAC_DRBG_generate_helper_Z HMAC key v (z + 32)).