This specification describes techniques for processing service requests. One example method includes receiving an electronic credential request from a client, retrieving an electronic credential that corresponds to the user identifier, generating server signature information, and transmitting the server signature information and the electronic credential to the client. The server signature information includes the electronic credential and a user public key of the client. The electronic credential and the user public are signed using a server private key. The server signature information is configured to be cryptographically verified by the client and configured to enable the client to generate a two-dimensional barcode based on the electronic credential. The electronic credential included in the two-dimensional barcode is configured to be verified by a credential verification device. The credential verification end device is configured to generate the electronic credential based on the user identifier.