  Smart contract access control mechanisms can introduce centralization into
supposedly decentralized ecosystems. In our view, such centralization is an
overlooked risk of smart contracts that underlies well-known smart contract
security incidents. Critically, mitigating the known vulnerability of missing
permission verification by implementing authorization patterns can in turn
introduce centralization. To delineate the issue, we define centralization risk
and describe smart contract source code patterns for Ethereum and Algorand that
can introduce it to smart contracts. We explain under which circumstances the
centralization can be exploited. Finally, we discuss implications of
centralization risk for different smart contract stakeholders.
