free c:channel.
free d:channel [private].

fun h(bitstring):bitstring.

const a,b:bitstring.

event A(bitstring).
event B(bitstring).

const ok,ko,k:bitstring[private].

axiom x:bitstring,y:bitstring; event(A(x)) ==> x=a && event(B(a)) [discardSat].


query x:bitstring;
        attacker(ok).

process
  (in(c,x:bitstring);
   event B(x);
   event A(x);
   out(d,x))
  | in(d,x:bitstring); if x <> a then out(c,ok)

(* EXPECTPV
RESULT not attacker(ok) is true.
0.008s (user 0.008s + system 0.000s), max rss 7312K
END *)
