Embodiments provide a communication method and apparatus and system for executing the method. The method includes sending a registration request message. The registration request message is usable to request registration with a network, and the registration request message includes an identifier of a terminal device. Activating a security context in response to authentication of the network by the terminal device succeeding. The security context is useable to protect secure communication between the terminal device and a network element. Performing integrity verification on a first message from the network element based on the security context. The first message is useable to request to perform a first operation on the terminal device. Performing the first operation in response to the integrity verification succeeding.