  Automata representing game-semantic models of programs are meant to operate
in environments whose input-output behaviour is constrained by the rules of a
game. This can lead to a notion of equivalence between states which is weaker
than the conventional notion of bisimulation, since not all actions are
available to the environment. An environment which attempts to break the rules
of the game is, effectively, mounting a low-level attack against a system. In
this paper we show how (and why) to enforce game rules in games-based hardware
synthesis and how to use this weaker notion of equivalence, called coherent
equivalence, to aggressively minimise automata.
