Every transaction that is processed on the Accumulate network has an actor, which is broadly defined as an entity that performs an action. For example, a Lite account is considered an actor when it creates an ADI, and an ADI is considered an actor when it creates a Key Book. When the protocol receives a transaction, the node loads the actor’s data record, locates the chain ID of the Key Book, and loads that particular Key Book. The transaction also specifies a Key Page priority, which refers to a Key Page within the key book that is associated with the actor. The keys in that Key Page are authorized to sign the transaction. If the transaction is signed by a key that is not in that Key Page, that signature is rejected.