Appearance data of a target entity is collected as appearance data, where the target entity comprises a physical entity capable of accessing, as a member, a blockchain. The appearance data is registered in a distributed database associated with the blockchain as an identity of the target entity. A target transaction initiated by a member node device in the blockchain is received, where the target transaction comprises the appearance data of the target entity that is collected by the member node device and a service event that is related to the target entity and that is detected by the member node device. A smart contract that corresponds to the service event is invoked. Based on the identity indicated by the appearance data of the target entity, service logic stated in the smart contract is executed.