(*We're using sum in the following because it appears to compute more nicely.*)

(*hexstring_to_int*)
Definition x2i s : int := Int.repr (hexstring_to_Z s).Goal sum (x2i "c0a8787e"%string)
         (x2i "9fd1161d"%string) =
     x2i "60798e9b"%string.Goal Int.xor (x2i "c0a8787e"%string)
         (x2i "9fd1161d"%string) =
     x2i "5f796e63"%string.Definition QuadWord:Type := (int * int * int * int)%type.Definition quarterround (y:QuadWord): QuadWord :=
  match y with (y0, y1, y2, y3) =>
    let z1 := Int.xor y1 (Int.rol (sum y0 y3) (Int.repr 7)) in
    let z2 := Int.xor y2 (Int.rol (sum y0 z1) (Int.repr 9)) in
    let z3 := Int.xor y3 (Int.rol (sum z1 z2) (Int.repr 13)) in
    let z0 := Int.xor y0 (Int.rol (sum z2 z3) (Int.repr 18))
    in (z0, z1, z2, z3)
  end.Definition quarterround_old (y:QuadWord): QuadWord :=
  match y with (y0, y1, y2, y3) =>
    let z1 := Int.xor y1 (Int.rol (sum y0 y3) (Int.repr 7)) in
    let z2 := Int.xor y2 (Int.rol (sum z1 y0) (Int.repr 9)) in
    let z3 := Int.xor y3 (Int.rol (sum z2 z1) (Int.repr 13)) in
    let z0 := Int.xor y0 (Int.rol (sum z3 z2) (Int.repr 18))
    in (z0, z1, z2, z3)
  end.

Lemma QR y: quarterround y = quarterround_old y.