fun tdcommit/3.
fun open/2.
fun f/4.

equation open(tdcommit(x,y,z),y) = z.
equation tdcommit(x2,f(x1,y,z,x2),z) = tdcommit(x1,y,z).
equation open(tdcommit(x1,y,z), f(x1,y,z,x2)) = x2.
equation f(x2,f(x1,y,z,x2),z,x3) = f(x1,y,z,x3).

free c,pk,s,t.

process out(c, choice[s,t])

