Implementations of the present disclosure provide techniques to improve security in blockchain networks. In some implementations, a linking request is received from a node. The node requests to be linked to a blockchain network. The linking request includes a digital code. One or more consensus verification messages are received from one or more blockchain nodes of the blockchain network. Each consensus verification message indicates whether a respective blockchain node approves or denies the linking request. A consensus verification result is determined based on the one or more consensus verification messages. In response to determining that the linking request is approved by the one or more blockchain nodes, the digital code is stored into the blockchain network as a digital certificate of the node.