Definition QuadWordRep (q:QuadWord):list val :=
  match q with (q0, q1, q2, q3) => map Vint [q0;q1;q2;q3] end.Definition SixteenWordRep (w:SixteenWord):list val :=
  match w with (q0, q1, q2, q3) => QuadWordRep q0 ++ QuadWordRep q1 ++ QuadWordRep q2 ++ QuadWordRep q3 end.Definition littleendian_of_SixteenByte (x:SixteenByte): QuadWord :=
  match x with (q0, q1, q2, q3) => (littleendian q0, littleendian q1, littleendian q2, littleendian q3) end.

Lemma SixteenWR_int s i: (0<=i<16)%nat -> exists ii, nth i (SixteenWordRep s) Vundef = Vint ii.