In contrast to both Bitcoin and Ethereum, Corda does not order transactions using a block chain and by implication does not use miners or proof-of-work. Instead each state points to a notary, which is a service that guarantees it will sign a transaction only if all the input states are un-consumed. A transaction is not allowed to consume states controlled by multiple notaries and thus there is never any need for two-phase commit between notaries. If a combination of states would cross notaries then a special transaction type is used to move them onto a single notary first. See §7 for more information.