Data transmission method, first device, and second device

A method for transmitting data, comprising:

• receiving, by a second device, a transmission message transmitted from a first device, wherein the transmission message comprises transmission data, and a security context identifier of an inactive terminal device;
• matching, by the second device, the security context identifier of the inactive terminal device with a security context identifier of at least one local terminal device;
• and
• deciding, by the second device, whether to active security of the inactive terminal device according to a result of the matching.

A second device, comprising:

• a processor, a memory, and a transceiver, wherein:
• the processor is configured to read and execute program in the memory:
• to receive, through the transceiver, a transmission message transmitted from a first device, wherein the transmission message comprises transmission data, and a security context identifier of an inactive terminal device;
• to match the security context identifier of the inactive terminal device in the transmission message received through the transceiver with a security context identifier of at least one local terminal device;
• and
• to decide whether to active security of the inactive terminal device according to a matching result.