fun sencrypt/2.
reduc sdecrypt(sencrypt(x,y),y) = x.

private free secret.
free e.

query	attacker : secret.

let processA =
	new cle;
	in(e,x);	
	if x = a then out(e,cle)
	else out(e,sencrypt(secret,cle)).

process new a;
	new b;
	out(e,a);
	out(e,b);
	!processA
		