The present invention provides an auxiliary display system, device and method. The auxiliary display system includes a client and a server. The client includes an auxiliary display unit which further includes a security module. The server generates information to be shown in the auxiliary display unit, and uses a shared encryption key of the auxiliary display unit to encrypt the information. The security module uses the shared encryption key to verify validity of encrypted information from the server, and decrypts the encrypted information so that the decrypted information will be shown in the auxiliary display unit. The present invention can prevent from forging the auxiliary display information by malicious programs and provide users with reliable information display, and improve experience of the users.