Hint Rewrite Znth_nthi using (auto; omega) : sublist.
Hint Resolve Zland_in_range.

Lemma sigma_0_eq:
forall s, sigma_0 s =
Int.xor
(Int.xor
(Int.or (Int.shl s (Int.repr 25))
(Int.shru s (Int.sub (Int.repr 32) (Int.repr 25))))
(Int.or (Int.shl s (Int.repr 14))
(Int.shru s (Int.sub (Int.repr 32) (Int.repr 14)))))
(Int.shru s (Int.repr 3)).