Transparent generate_word.

(* Specifications: *)
Lemma generate_word_lemma1:
forall b n, length b = 16%nat ->
firstn 16 (rev (generate_word (rev b) n)) = b.
Lemma length_generate_word: forall b n,
length (generate_word b n) = (length b + n)%nat.
Lemma nth_generate_word_S:
forall k i n b',
nth (i+k) (generate_word b' (n+k)) = nth i (generate_word b' n).
Lemma generate_word_small:
forall i b n,
length b = 16%nat ->
(i < length b)%nat ->
nth i (rev (generate_word (rev b) n)) = nth i b.
Lemma generate_word_plus:
forall msg a b, (16 <= length msg)%nat ->
generate_word msg (a+b) = generate_word (generate_word msg a) b.