A first communication request including a digital certificate of a first node sent from the first node in a blockchain is received at a second node in the blockchain, where the digital certificate of the first node is stored in the blockchain. Certificate validity information stored in the blockchain and associated with the nodes in the blockchain is accessed by the second node based on the first communication request, where the certificate validity information reflects the validity status information of digital certificates of the nodes in the blockchain. A verification of whether the digital certificate of the first node is valid is performed by the second node based on the first communication request and the accessed certificate validity information. A communication connection to the first node is established by the second node in response to verifying that the digital certificate of the first node is valid.