  Complex DeFi services are usually constructed by composing a variety of
simpler smart contracts. The permissionless nature of the blockchains where
these smart contracts are executed makes DeFi services exposed to security
risks, since adversaries can target any of the underlying contracts to
economically damage the compound service. We introduce a new notion of secure
composability of smart contracts, which ensures that adversaries cannot
economically harm the compound contract by interfering with its dependencies.
