free c:channel.

fun h(bitstring):bitstring.

const a,b:bitstring.

free k:bitstring [private].

event A(bitstring).
event B.

const ok,ko:bitstring.

not attacker(k).

process
  in(c,x:bitstring);
  if x = diff[a,a]
  then
    event A(a);
    out(c,diff[k,k])
  else
    out(c,ko)

(* EXPECTPV
Error: you have given a secrecy assumption that I could not verify.
xtime: error in child process (status : 2)
END *)
