Family key is symmetric

As I understand it, the Skipjack system is symmetric, i.e., decrypt key= encrypt key. Also, the unit serial number seems to only get encrypted with the family key. So, once the family key and the algorithm are known, it will be possible to create messages with any unit serial number you want, right? Wouldn't this be enough to foil the casual traffic-analysis feature of the crippler? --fnerd the keyhole chip the wing clipper co-intel inside as seen on whitehouse stationery only open a crack the taped lock cyphergate "Daffy, you quack me up." --Elmer