A combinatorial auction mechanism consists of an allocation rule that defines the allocation of goods for each agent, and a payment rule that defines the payment of each winner. There have been several studies on characterizing strategyproof allocation rules. In particular, a condition called weakmonotonicity has been identified as a full characterization of strategy-proof allocation rules. More specifically, for an allocation rule, there exists an appropriate payment rule so that the mechanism becomes strategy-proof if and only if it satisfies weak-monotonicity. In this paper, we identify a condition called sub-additivity which characterizes false-name-proof allocation rules. Falsename-proofness generalizes strategy-proofness, by assuming that a bidder can submit multiple bids under fictitious identifiers. As far as the authors are aware, this is the first attempt to characterize false-name-proof allocation rules. We can utilize this characterization for developing a new fals...