For private chain setups, Parity supports a Proof-of-Authority (PoA) consensus engine to be used as a replacement for the Proof-of-Work (PoW) consensus engine. Proof-of-Authority does not depend on nodes solving arbitrarily difficult mathematical problems, but instead uses a hard-configured set of "authorities" - nodes that are explicitly allowed to create new blocks and secure the blockchain. This makes it easier to maintain a private chain and keep the block issuers accountable.