Encryption in a wireless telecommunications

1. A method of transmitting encrypted user data to a mobile terminal in a wireless telecommunications network, the method comprising:

sending to the mobile terminal a data packet, the data packet comprising both:

an identifier of encryption information for use by the mobile terminal in initializing a security context that enables the mobile terminal to recover encrypted user data in response to receipt of the data packet, and

user data encrypted using said encryption information;

wherein the network comprises an LTE network;

wherein the data packet comprises a Security Mode Command, the Security Mode Command comprising the identifier of the encryption information.

2. A method according to claim 1 , wherein the identifier of the encryption information comprises an identifier of an encryption algorithm.

3. A method according to claim 2 , wherein the encryption information comprises an encryption key.

4. A method according to claim 2 , wherein the user data comprises user traffic data.

5. A method according to claim 2 , further comprising the step of the mobile terminal using the identified encryption information to recover the user data.

6. A method according to claim 5 , further comprising the mobile terminal storing the identified encryption information for use in recovering encrypted user data in a subsequently received data packet.

7. A method according to claim 1 , wherein the user data comprises user signaling data.

8. A method according to claim 7 , wherein the user signaling data comprises an NAS message or an RRC message.

9. A method according to claim 1 , further comprising the step of the mobile terminal using the identified encryption information to recover the user data.

10. A method according to claim 9 , further comprising the mobile terminal storing the identified encryption information for use in recovering encrypted user data in a subsequently received data packet.

11. A method according to claim 1 , wherein the user data comprises user traffic data.

12. A method according to claim 1 , wherein the encryption information comprises an encryption key.

13. An LTE wireless telecommunications base station comprising:

a transmitter adapted to transmit encrypted user data in a data packet, the data packet comprising:

an identifier of encryption information transmitted for the first time, said encryption information being adapted to be used in a receiver to recover encrypted user data, and

user data encrypted using said encryption information;

wherein the data packet comprises a Security Mode Command, the Security Mode Command comprising the identifier of the encryption information.

14. A wireless telecommunications terminal comprising:

a receiver; and

a processor;

wherein the receiver is adapted to receive a data packet, the data packet comprising both an identifier of encryption information to be used in recovering encrypted user data, and user data encrypted using said encryption information;

wherein in response to receipt of the data packet, the wireless telecommunications terminal initializes a security context using the identified encryption information;

wherein the processor is adapted to use said encryption information to recover the user data encrypted using said encryption information, the wireless telecommunications mobile terminal being adapted to store said encryption information for subsequent use;

wherein the terminal is an LTE wireless telecommunications terminal; and

wherein the data packet comprises a Security Mode Command, the Security Mode Command comprising the identifier of the encryption information.

15. A wireless telecommunications terminal according to claim 14 , wherein the processor is shared by the receiver.

16. A method for use by a mobile terminal in a wireless telecommunications network receiving encrypted user data, the method comprising:

receiving a first data packet at the mobile terminal, the first data packet comprising user data encrypted using first encryption information;

recovering the user data in the mobile terminal using the first encryption information stored in the mobile terminal;

receiving a next data packet at the mobile terminal, the next data packet comprising both an identifier of updated encryption information to be used in recovering encrypted user data in said next data packet, and user data encrypted using said updated encryption information;

wherein the mobile terminal is an LTE wireless telecommunications terminal; and

wherein the data packet comprises a Security Mode Command, the Security Mode Command comprising the identifier of the encryption information.

17. A method according to claim 16 , further comprising the step of the mobile terminal initializing a security context using the identified updated encryption information in response to receipt of said next data packet at the mobile terminal.

18. A method according to claim 17 , further comprising the step of the mobile terminal using said updated encryption information to recover the user data encrypted in said next data packet using said updated encryption information.

19. A method according to claim 18 , further comprising the step of the mobile terminal storing said updated encryption information for subsequent use in decrypting subsequent packets.

20. A wireless telecommunications terminal comprising:

means for receiving a data packet, the data packet comprising both an identifier of encryption information to be used in recovering encrypted user data, and user data encrypted using said encryption information;

means for initializing a security context of said wireless telecommunications terminal using the identified encryption information in response to receipt of said data packet;

means for recovering said user data encrypted using said encryption information; and

means for storing said encryption information for subsequent use;

wherein said terminal is an LTE wireless telecommunications terminal; and

wherein the data packet comprises a Security Mode Command, the Security Mode Command comprising the identifier of the encryption information.

21. A wireless telecommunications terminal according to claim 20 , wherein said means for receiving said data packet comprises a receiver of the wireless telecommunications terminal.

22. A wireless telecommunications terminal according to claim 20 , wherein said means for recovering said user data comprises at least one processor of the wireless telecommunications terminal.

23. A method of transmitting encrypted user data to a mobile terminal in a wireless telecommunications network, the method comprising:

sending to the mobile terminal a data packet, the data packet comprising both:

user data encrypted using encryption information; and

an identifier of said encryption information which is useable by the mobile terminal to initialize a security context for use in recovering said encrypted user data;

wherein the network comprises an LTE network; and

wherein the data packet comprises a Security Mode Command, the Security Mode Command comprising the identifier of the encryption information.