A method, wherein the method comprises the steps of: • when a server receives a group joining request that is sent by a first terminal and that is used for joining a trusted group, generating, by the server, a first certificate for the first terminal based on a first version number (step 104), wherein the trusted group is formed by a plurality of terminals; • sending, by the server, the first certificate and the first version number to the first terminal (step 105); • when the server determines that a second terminal is removed from the trusted group, updating, by the server, the first version number to a second version number according to a preset rule (step 202); • generating, for each terminal not being removed from the trusted group, by the server based on the second version number, a corresponding second certificate (step 203); • separately sending, by the server, the corresponding second certificate and the second version number to those terminals not removed from the trusted group (step 204); the method being characterized by the further steps of: • receiving, by the first terminal, an authentication request sent by a third terminal, where the authentication request includes a version number and an identifier of the third terminal; • the first terminal stores a device list sent by the server, the device list includes recorded information of all the terminals not removed from the trusted group, and the recorded information includes an identifier and a public key of each terminal not removed from the trusted group; • when determining that the version number of the third terminal is less than or equal to the second version number, the first terminal determines whether the device list includes recorded information of the third terminal; the first terminal may match the received identifier sent by the third terminal with the recorded information in the device list; and when there is a same matched result, the first terminal determines that the identity of the third terminal is valid. • when a server receives a group joining request that is sent by a first terminal and that is used for joining a trusted group, generating, by the server, a first certificate for the first terminal based on a first version number (step 104), wherein the trusted group is formed by a plurality of terminals; • sending, by the server, the first certificate and the first version number to the first terminal (step 105); • when the server determines that a second terminal is removed from the trusted group, updating, by the server, the first version number to a second version number according to a preset rule (step 202); • generating, for each terminal not being removed from the trusted group, by the server based on the second version number, a corresponding second certificate (step 203); • separately sending, by the server, the corresponding second certificate and the second version number to those terminals not removed from the trusted group (step 204); the method being characterized by the further steps of: • receiving, by the first terminal, an authentication request sent by a third terminal, where the authentication request includes a version number and an identifier of the third terminal; • the first terminal stores a device list sent by the server, the device list includes recorded information of all the terminals not removed from the trusted group, and the recorded information includes an identifier and a public key of each terminal not removed from the trusted group; • when determining that the version number of the third terminal is less than or equal to the second version number, the first terminal determines whether the device list includes recorded information of the third terminal; the first terminal may match the received identifier sent by the third terminal with the recorded information in the device list; and when there is a same matched result, the first terminal determines that the identity of the third terminal is valid. <EOS>