Method of operation of a terminal device in a cellular communications network
A method of operation of a terminal device in a cellular communications network is disclosed. The method comprises sending a GMM Attach Request message to the network, the GMM Attach Request message identifying security capabilities of the terminal device. The terminal device receiving from the network an echo message in the GMM layer including information identifying the security capabilities of the terminal device, wherein the echo message is received with integrity protection.
1. A method of operation of a terminal device in a cellular communications network, the method comprising:
sending a General Packet Radio Service (GPRS) Mobility Management Attach Request message to the network, the GPRS Mobility Management (GMM) Attach Request message identifying security capabilities of the terminal device; and
receiving from the network an echo message in a GMM layer including information identifying the security capabilities of the terminal device, wherein the echo message is received with integrity protection.
2. The method of claim 1 , wherein the integrity protection is provided by a Message Authentication Code in the echo message.
3. The method of claim 1 , wherein the echo message is a GMM Authentication and Ciphering Request message.
4. The method of claim 1 , wherein the security capabilities identified in the GMM Attach Request message include at least one of: an integrity protection algorithm supported by the terminal device or an encryption algorithm supported by the terminal device.
5. The method of claim 4 , wherein the echo message further includes information identifying at least one of: an integrity protection algorithm selected by the network and supported by the terminal device or an encryption algorithm selected by the network and supported by the terminal device.
6. The method of claim 1 , further comprising:
verifying a Message Authentication Code included in the echo message.
7. The method of claim 6 , further comprising verifying the Message Authentication Code in the GMM protocol layer in the terminal device.
8. The method of claim 6 , further comprising verifying the Message Authentication Code in the terminal device using a counter value.
9. The method of claim 8 , wherein the counter value includes bits of a random number (RAND) value.
10. The method of claim 6 , further comprising, if the Message Authentication Code is verified:
determining whether the security capabilities of the terminal device identified in the echo message match the security capabilities of the terminal device identified in the GMM Attach Request message; and
maintaining the connection with the network only if the security capabilities of the terminal device identified in the echo message do match the security capabilities of the terminal device identified in the GMM Attach Request message.
11. The method of claim 10 , further comprising, if the security capabilities of the terminal device identified in the echo message do match the security capabilities of the terminal device identified in the GMM Attach Request message:
deriving at least one security key; and
activating integrity protection in a Logical Link Control (LLC) protocol layer by assigning the derived security key to the LLC protocol layer.
12. A terminal device for use in a cellular communications network, the terminal device being configured to:
send a General Packet Radio Service (GPRS) Mobility Management Attach Request message to the network, the GPRS Mobility Management (GMM) Attach Request message identifying security capabilities of the terminal device; and
receive from the network an echo message in a GMM layer including information identifying the security capabilities of the terminal device, wherein the echo message is received with integrity protection.
13. A method of operation of a network node in a cellular communications network, the method comprising:
receiving a General Packet Radio Service (GPRS) Mobility Management Attach Request message from a terminal device, the GPRS Mobility Management (GMM) Attach Request message identifying security capabilities of the terminal device; and
transmitting to the terminal device an echo message in a GMM layer,
wherein the echo message includes information identifying the security capabilities of the terminal device, corresponding to the security capabilities identified in the GMM Attach Request message, and
the method further comprises transmitting the echo message with integrity protection.
14. The method of claim 13 , wherein the integrity protection is provided by a Message Authentication Code in the echo message.
15. The method of claim 13 , wherein the echo message is a GMM Authentication and Ciphering Request message.
16. The method of claim 13 , wherein the security capabilities identified in the GMM Attach Request message include at least one of: an integrity protection algorithm supported by the terminal device or an encryption algorithm supported by the terminal device.
17. The method of claim 16 , wherein the echo message further includes information identifying at least one of: an integrity protection algorithm selected by the network and supported by the terminal device or an encryption algorithm selected by the network and supported by the terminal device.
18. The method of claim 13 , further comprising activating integrity protection in a Logical Link Control (LLC) protocol layer after receiving from the terminal device a response indicating successful authentication with the network.
19. The method of claim 18 , wherein the response indicating successful authentication with the network is a GMM message.
20. The method of claim 19 , wherein the response indicating successful authentication with the network is a GMM Authentication and Ciphering Response message.
21. The method of claim 18 , wherein the security key used for integrity protection in the LLC protocol layer is the same as the key used for integrity protection in the GMM layer.
22. The method of claim 18 , wherein the security key used for integrity protection in the LLC protocol layer is different from the key used for integrity protection in the GMM layer.
23. A network node for use in a cellular communications network, being configured to:
receive a General Packet Radio Service (GPRS) Mobility Management Attach Request message from a terminal device, the GPRS Mobility Management (GMM) Attach Request message identifying security capabilities of the terminal device;
transmit to the terminal device an echo message in a GMM layer, wherein the echo message includes information identifying the security capabilities of the terminal device, corresponding to the security capabilities identified in the GMM Attach Request message; and
transmit the echo message with integrity protection.
24. The network node of claim 23 , wherein the network node is further configured to activate integrity protection in a Logical Link Control (LLC) protocol layer after receiving from the terminal device a response indicating successful authentication with the network.