Admitted.

Lemma Zlength_partially_expanded_key: forall i key_chars,
0 <= i < 7 ->
Zlength key_chars = 32 ->
Zlength (map Vint (pow_fun GrowKeyByOne (Z.to_nat (i * 8)) (key_bytes_to_key_words key_chars)) ++
repeat_op_table (60 - i * 8) Vundef id) = 68.