Parameter sending method and apparatus

A method, wherein the method comprises:

• sending, in an authentication process, a random number and a first sequence number to a terminal device;
• receiving a synchronization failure message from the terminal device, wherein the synchronization failure message carries a synchronization failure parameter;
• obtaining a message authentication code from the synchronization failure parameter;
• and
• obtaining a second sequence number from the synchronization failure parameter based on an authentication key, wherein the authentication key is generated based on a first parameter and a first reference value, and the first reference value is generated based on a second parameter and a third parameter, wherein each of the first parameter, the second parameter, and the third parameter comprises any one of the following:
• the random number, a key K of the terminal device, or the message authentication code.

A method, wherein the method comprises:

• receiving, in an authentication process, a random number and a first sequence number from a core network device;
• after determining that a difference between the first sequence number and a locally prestored second sequence number is greater than a threshold, performing symmetric encryption on the locally prestored second sequence number by using an authentication key to generate a synchronization failure parameter, wherein the authentication key is generated based on the random number and a locally prestored key K;
• and
• sending a synchronization failure message to the core network device, wherein the synchronization failure message carries the synchronization failure parameter.

A method, wherein the method comprises:

• sending, in an authentication process, a random number and a first sequence number to a terminal device;
• receiving a synchronization failure message from the terminal device, wherein the synchronization failure message carries a synchronization failure parameter;
• and
• performing symmetric decryption on the synchronization failure parameter based on an authentication key to obtain a second sequence number, wherein the authentication key is generated based on the random number and a key K of the terminal device.

A communication apparatus, comprising at least one processor and one or more memories, wherein the one or more memories are coupled to the at least one processor and store programming instructions for execution by the at least one processor to:

• receive, in an authentication process, a random number and a first sequence number from a core network device;
• after determining that a difference between the first sequence number and a locally prestored second sequence number is greater than a threshold, concatenate a message authentication code after an exclusive OR value of an authentication key and the locally prestored second sequence number to generate a synchronization failure parameter, wherein the authentication key is generated based on a first parameter and a first reference value, and the first reference value is generated based on a second parameter and a third parameter, wherein each of the first parameter, the second parameter, and the third parameter comprises any one of the following:
• the random number, a locally prestored key K, or the message authentication code;
• and
• send a synchronization failure message to the core network device, wherein the synchronization failure message carries the synchronization failure parameter.

A communication apparatus, comprising at least one processor and one or more memories, wherein the one or more memories are coupled to the at least one processor and store programming instructions for execution by the at least one processor to:

• send, in an authentication process, a random number and a first sequence number to a terminal device;
• receive a synchronization failure message from the terminal device, wherein the synchronization failure message carries a synchronization failure parameter;
• obtain a message authentication code from the synchronization failure parameter;
• and
• obtain a second sequence number from the synchronization failure parameter based on an authentication key, wherein the authentication key is generated based on a first parameter and a first reference value, and the first reference value is generated based on a second parameter and a third parameter, wherein each of the first parameter, the second parameter, and the third parameter comprises any one of the following:
• the random number, a key K of the terminal device, or the message authentication code.