Here: http://developer.mintchipchallenge.com/devguide/developing/c...
Each transfer message has both the Sender and Receiver encoded within it. These are opaque but generated by your mintchip provider.
Looking here: http://developer.mintchipchallenge.com/devguide/ecosystem.ht...
Suggests that your provider ("trusted broker") creates your mintchip ids. It might be possible to associate many keys to your physical person but I believe all of them could be traced back with the co-operation of the providers.