  We present models for utilizing blockchain and smart contract technology with
the widely used OAuth 2.0 open authorization framework to provide delegated
authorization for constrained IoT devices. The models involve different
tradeoffs in terms of privacy, delay, and cost, while exploiting key advantages
of blockchains and smart contracts. These include linking payments to
authorization grants, immutably recording authorization information and
policies in smart contracts, and offering resilience through the execution of
smart contract code on all blockchain nodes.
